HANDBOOK FOR REDUCING BASEMENT FLOODING
Option 1: Visit your municipal government's website or contact the public works, utilities or building department to find out about basement flooding
Review your municipality’s website or talk to officials in your municipal government about basement flooding. In most cases, they will be able to point you toward useful information on flood problems in your community, and what homeowners can do to reduce flooding in their homes and neighbourhood. Here are a few questions you should consider when talking to your municipal government:
What is your municipality doing to address flooding in your community and neighbourhood?
Has the municipality conducted any engineering studies on flooding in your community? If they have, do the studies provide recommendations on what homeowners can do to reduce flood risk?
Are any sewer system improvements planned in your area? Are there any upcoming flood related public meetings or workshops that you could attend to learn more about basement flooding?
Are there any opportunities to share your experience with basement flooding (for example, at public meetings)?
Does your municipality provide flood reduction guidance and education for homeowners?
In most cases, your municipal government is the best source of information on how to reduce flooding in your home and neighbourhood.
Does your municipal government provide financial assistance for basement flood reduction measures?
Some municipalities provide partial financial assistance for homeowners to install or alter plumbing and lot characteristics to reduce flood risk. Financial assistance may be provided for:
• Disconnecting eavestrough downspouts (see Option 12).
• Disconnecting weeping tiles from sanitary sewer laterals and installing sump-pits and sump-pumps (see Option 14).
• Installing backwater valves (see Option 15).
Talk to your municipal government to see if there is a similar program in your community. Your municipal government may also inspect and repair sewer laterals as a free service on a one-time basis.
Does your municipality provide a list of pre-qualified plumbers and contractors?
Hiring plumbers and contractors recommended by your municipal government will help to ensure that the right construction practices and materials are used when flood reduction measures are incorporated into your home. Using pre-qualified professionals will also ensure that the right plumbing devices are installed properly, and that you are getting a fair price for plumbing work.
Ask about all necessary permits, underground utility location services and inspection services
When talking to your municipal government, ask about all required permits, site visits and inspections that will be required for changes to your home’s plumbing and lot drainage. Remember to ask about underground utility locating policies and services, which may be required to identify the location of your home’s sewer laterals and other underground services before you dig up sections of your lot to access weeping tiles or sewer laterals.
Underground utility location and inspection services provided by municipal governments or utility companies may take several days or possibly weeks to complete, so inquire about them early in the process. These services may be free or may require a payment. As well, your municipal government may require work to be completed within a limited time-frame after underground utility location or inspection services have been performed. If you are hiring a professional to work on your home, ensure that they have discussed all of the necessary procedures with the municipal government, and that any site work that will be completed by utility companies or your municipal government is coordinated so that your flood reduction work goes smoothly.
Option 2: Talk to your government about basement flooding that you've experienced
If you have basement flooding, let your municipal government know about it during or after the event. In many cases, municipal governments may ask homeowners to fill out a questionnaire or comment on their experience at public meetings. Municipal governments can use this information to identify solutions and carry out work on reducing flood risk in your neighbourhood.
If possible, record the following details when you have basement flooding so you can report them to your municipal government. Try to take pictures or videos of the flooding and flood damage. DO NOT gather this information unless it is safe to do so. Do not enter your basement while it is being flooded or when there is water present. This could lead to drowning or electrical shock.
• What was the date and time of flooding?
• Did the basement flooding occur because of rain, snow-melt or a combination of rain and snow-melt?
• Approximately how long was the rainstorm? Did the rainstorm appear to be extremely heavy, moderate or light?
• Were you using internal pumbing such as dishwashers, showers or laundry machines during the flooding?
• Was there any overland flooding in your neighbourhood?
– Was it flowing over private properties?
– If there was water flowing over the surface outside of your home, approximately how deep was it?
• How deep was the water in your basement?
• How did the water get into your home?
– Did it get in through windows, doors or vents?
– Did it seep in through cracks in the basement walls and floor?
– Did it come up through plumbing fixtures and floor drains?
• How did the water leave your basement?
– Did it eventually flow out through floor drains or did you have it pumped out?
• If you had a sump-pump, did it work properly?
• If you had a backwater valve, did it work properly?
• Did you hire a contractor, plumber, repair crew or cleaning crew to investigate the flooding incident or make repairs?
• Did you make an insurance claim?
• Was your claim denied or approved?
Option 3: Hire a licensed plumber to conduct a detailed plumbing inspection on your home
Each home is unique. A plumber or contractor who is fully versed in home and municipal drainage systems can help you understand the risk of flooding in your home. Some homes may have only a sanitary sewer lateral and some homes may have both a sanitary sewer lateral and a storm sewer lateral. Understanding the risks of flooding and the nature of your plumbing and sewer connections will help to ensure that the best course of action is taken to reduce future flooding in your home.
If possible, hire contractors or plumbers who have been pre-approved and recommended by your municipal government.
Contact the public works, utilities or building department in your municipal government and ask for a list of contractors or plumbers who have been pre-approved to carry out work related to basement flooding.
A detailed plumbing investigation may involve the use of closed circuit television (CCTV) camera inspections. This type of inspection will help to identify the type of connections that a home has to the municipal sewer system and the nature of the home’s plumbing.
Option 4: Check your insurance policy, or talk to your insurance provider or broker
Here are a few points to consider when thinking about your home insurance coverage for basement flooding:
• Does your home insurance policy cover sewer backup damage?
• Did you know that the vast majority of Canadian homeowners are not covered for damages caused by overland flooding or infiltration flooding?
• There have been cases where homeowners who have made repeated claims for sewer backup damage have experienced capping of their eligible sewer backup payouts, or cancellation of sewer backup coverage altogether.
Talk to your insurance provider or broker to find out about what types of flood damages are covered under your policy. Trying to make a claim after you have suffered basement flood damages is not a good way to find out that you didn’t have the proper coverage, or that some types of flooding are uninsurable.
You should also make sure that your insurance policy is up-to-date, and reflects any up-grades or renovations you have made to your home. This will increase the chances that you will receive an adequate payout from your insurance company when you make an insurance claim.
Option 5: Avoid pouring fats, oils and grease (FOGs) down your drains
Fats, oils and grease (FOGS) are by-products of preparing food and cleaning dishes, pots and pans. Over time, FOGS can build up in your sanitary lateral, or in the municipal sanitary sewer and cause blockages, which can result in sewer backup.
Instead of rinsing grease down your kitchen drain, wipe it off with a paper towel and put it in with your food waste, or wait until the grease congeals and dispose of it with your food waste. If you have FOGS to dispose of that won’t congeal, pour them into a disposable water tight container and place the container in the garbage.
If you have a lot of FOGS to dispose of, talk to your municipal government to see if there is a disposal program for large quantities of household FOGS
Option 6: Keep storm sewer grates clear
When storm sewer grates are clogged with yard waste, leaves, garbage, snow and ice or other debris, less water will enter the storm sewer system. When water can’t get into the sewer system, there is an increased chance that it will flow onto private properties and then into homes and basements. Here are a few things you can do to help keep storm sewer grates clear and working properly:
• Does your community have a yard waste pickup program? If it does, wait until the day that your yard waste will be picked up before placing it on the curb.
• If you live in an older neighbourhood that is densely-treed, watch for blockages in storm sewer grates from fallen leaves, especially during the fall months.
• Put out your garbage on collection days only.
• If you notice that a sewer grate is clogged with any debris including snow and ice, clear it out or let your municipal government know about it. If a storm sewer grate is repeatedly blocked or has a poor ability to drain water from the surface, it may be a sign of a larger problem in the catch basin. If you notice such a sewer grate, inform your municipal government. It may well save you and your neighbours from having basement flood damages.
Option 7: Seal cracks in foundation walls and basement floor
Sealing cracks is a simple way to help reduce basement flooding in your home and neighbourhood. Sealing cracks will help you reduce the chances that you’ll have infiltration flooding, and can reduce the amount of flood water that enters the municipal sanitary sewer system through your basement floor drain. In many cases, cracks can be effectively sealed from inside the basement, and you will not have to dig anywhere beside the foundation to repair them.
Talk to a plumber, contractor or check your local hardware or home improvement store for the best types of products for this job. If cracks appear to be severe, you may require the assistance of a qualified contractor or structural engineer, as severe cracks may represent a structural issue with the home and may require more substantial repairs.
Option 8: Considerations for overland flood entry-points
During an overland flood event, water can enter basements from unsealed openings in basement walls. These openings may include gaps between the basement wall and the framing around windows and doors, gaps around electrical wiring, phone and television cables and gaps around pipes and other services that enter the basement. Cracks in brickwork can also provide entry-points for overland floodwater. These gaps should be indentified and sealed.
Newer windows that have been properly installed are better able to hold back floodwater than older windows where framing, weather stripping and sealants have deteriorated. Newer window frames made from synthetic materials, rather than wood, can also help to reduce the chances that water will enter the basement.
The gap between door and window frames can be sealed to reduce the chances that water will seep between the door or window and the wall. The use of proper weather stripping in windows and doors can also reduce the chances that overland flooding will enter the basement. There are also opportunities to use glass in basement windows that is stronger and better able to hold back overland flood water. Talk to a qualified contractor to explore these and other options for sealing water entry-points in your basement.
Option 9: Reduce home water use during heavy rainfall events
During a heavy rainfall event, do whatever you can to reduce the amount of water you are putting into the municipal sewer system. The more stress placed on the municipal system, the greater the chances that you or your neighbours will have sewer backup problems. This is especially important if you have a backwater valve (see Option 15).
Waiting to do your laundry, run your dishwasher or use the bathroom until a few hours after a severe rainfall event can help reduce your chances and your neighbours’ chances of basement flooding.
Option 10: Maintain eavestroughs and downspouts
Regularly clean and maintain your eavestroughs and downspouts to make sure they are not clogged with debris. When eavestroughs and downspouts are clogged, water can pour over the side of eavestroughs, fall close to your home, and then run down the side of your foundation. Water can also pour into window wells, which may be connected to weeping tiles through a drainage pipe. If this water enters your weeping tile, or your basement through cracks in the foundation, this will increase the chances that you and your neighbours will have basement flooding.
Option 11: Avoid storing items directly on the basement floor
Keep things a few inches off the floor in your basement. If you are storing things on shelves, try not to use the bottom shelf, or try placing items on a solid foundation a few inches or feet off the ground. For example, arrange cinder blocks or bricks beneath important items to help raise them off the ground. If you must keep important documents or items in the basement, store them in watertight plastic containers to reduce their chances of being damaged if the basement floods.
If you can find out what a likely flood level might be in your home, you should elevate your possessions based on that level. Talk to your municipal government to see if this information is available.
Option 12: Downspout disconnection, extensions and splash pads
Downspouts are designed to convey water from eavestroughs and down the side of the house. Downspouts often direct water to the surface of the lot, but in many cases they may be connected to the weeping tile or the sanitary
sewer lateral. When connected to the municipal sewer system, eavestrough downspouts can contribute a substantial amount of water to these systems. Because of the environmental impacts resulting from combined sewer overflows and the increase in flood risk connected eavestroughs cause, it is illegal to connect downspouts to municipal sewer systems in many Canadian communities.
In some cases, downspouts may be connected to the municipal storm sewer system through a separate storm sewer lateral. If your downspout leads to an underground pipe, you should contact the department responsible for urban drainage in the municipal government. They should be able to tell you if your downspout should be connected to the sewer system, or if it should be directed over your lot. Identifying what the downspout is connected to should be part of the detailed plumbing investigation in your home (see Option 3).
When the downspout is disconnected from an underground pipe, the remaining exposed pipe leading underground should be capped to stop extra water from entering the sewer system. A 1.8 metre extension should be placed on the downspout to ensure that water is kept away from the home, and splash pads should be used help prevent erosion at the discharge point. Downspout water should be directed over a permeable surface, including lawns and gardens. A pipe can be used to direct flow to a lawn if the area surrounding the downspout is paved.
When downspouts are directed over a lot’s surface, they create the potential for damage, including flooding, erosion and ice build up, for neighbouring properties. You should consult your municipal government to ensure that downspouts are directing flows in a manner that does not negatively affect neighbouring properties.
A further benefit of disconnecting downspouts is that water from downspouts can be directed over permeable surfaces, thereby reducing the amount of water that enters municipal sewer systems. Reducing water that enters these systems can decrease the risk of flooding for you and your neighbours, and can reduce the environmental impacts of stormwater flows.
You may also consider installing a rain barrel when you are disconnecting your downspout. This will allow you to store some of the water that flows off of your roof so that you can use it during dry periods in the summer. If a rain barrel is to be installed, consider the following points:
• Rain barrels are not designed to capture a large volume of water during a storm, and will overflow during heavy downpours.
• Make sure that, when the barrel has filled with water during prolonged rain events, overflow is directed away from your foundation wall and onto a splash pad at least 1.8 metres away from
• During the winter, the rain barrel should be disconnected from the downspout to prevent damage from ice build-up in the barrel.
• Some municipalities will provide a partial subsidy for installing a rain-barrel, as they can help to reduce water use during the dry summer months.
• Water collected in rain barrels is unsuitable for drinking or other domestic uses, and should only be used to water gardens and lawns.
Follow manufacturer’s instructions for installation, operation and maintenance for the rain barrel.
Option 13: Lot grading, backfilling and swales
If you’ve ever had a look around newly constructed homes, you might notice that yards are gently graded away from houses. When a yard is graded in this manner, it helps keep water away from the home and foundation, and helps keep the basement dry. Most municipal governments in Canada have bylaws that require lot grading that directs water away from the home, as a properly graded yard can substantially reduce basement flood and moisture problems.
Over time, however, yards can lose this slope for a number of reasons. For example, landscaping work can impact lot grading, and over time, soil may settle and result in lot grading that directs water toward the home and foundation. New decks, additions to homes or alterations to your neighbour’s properties can also affect lot grading around your home.
When regrading lots to direct water flows away from the home, the following points should be considered:
• A drop of 10 to 15 cm over 1.5 metres from the wall of your home may be required to adequately direct water away from the home.
• Lot grading should direct water to an acceptable drainage outlet that can direct flows to municipal conveyance systems. Consult your local government to ensure that water from your lot is directed to the right place.
• Ensure that lot grading does not direct water in such a way as to create ice build-up on neighbouring properties or sidewalks.
• Ensure that water flows from your lot do not negatively affect neighbouring properties.
Swales are grassy depressions, like a shallow ditch, that help direct the flow of water away from homes. Swales generally direct water toward drainage infrastructure, including roadways or storm sewer catch basins. The same factors that affect lot grading can affect swales. For example, landscaping and the settling of soil can both damage swales.
Sheds and fences should not be placed in a manner that blocks drainage paths or catch basins. Consult your municipality to see if a drainage plan for your subdivision exists, and ensure you maintain the intended drainage plan if you are going to alter your yard by building fences or sheds.
When your home was constructed, the basement was dug from undisturbed soil. After the foundation was completed, soil was pushed back into the gap between your foundation walls and the undisturbed soil. This soil is not as compact as the rest of the undisturbed soil surrounding the foundation. This less compact soil is more permeable, and allows water to infiltrate into the ground beside the foundation.
Permeable soil next to the foundation can increase the chances of infiltration flooding in the home, and can increase flows into the weeping tile. If the weeping tile is connected to the municipal sewer system, excess water can increase overland flooding and sewer backup risk in the neighbourhood. If the weeping tile has been disconnected from the municipal system and is drained into a sump-pit, the sump-pump will have to run longer to pump excess water flows from the weeping tile.
As part of the lot grading improvements, a compact soil should be used to fill in any depressed areas directly beside the foundation wall. A compact soil, such as clay, should also be used to “cap” the backfill area, and should be properly sloped to keep water away from the home.
Option 14: Weeping tiles, sump-pits and sump-pumps
A foundation drain is an underground perforated pipe, or weeping tile, that runs along the bottom of a home’s foundation. The weeping tile helps keep the basement free of excess and is also very useful for helping to reduce infiltration flooding. The water that is conveyed by the weeping tile is relatively clean, and does not normally require treatment at sanitary sewage treatment facilities.
Here are some questions you should consider when thinking about foundation drains and weeping tiles:
Does my home have a foundation drain?
An assessment of whether or not your home has a foundation drain should be conducted during the detailed plumbing investigation of your home (see Option 3). Older Canadian homes, for example those built before the 1940s or 1950s, may not have foundation drains. If you find that your home does not have a foundation drain, you should consider having one installed. Make sure that you have the proper permits from your municipal government and that the work is undertaken by licensed trades people. This will likely be an expensive job; however, it can have a substantial impact on reducing water damage in your basement.
Are there any problems with the foundation drain?
Over time, weeping tiles may become clogged with debris or may collapse in some sections. When weeping tiles are not in good working order, they will not be able to effectively remove water from the foundation. A review of the foundation drainage should be included as part of the detailed plumbing investigation of the home (see Option 3).
If the home has older weeping tiles made of clay or concrete, the replacement of the entire system with new perforated plastic pipes may be necessary, as older weeping tiles are more susceptible to collapsing and blockages. If replacing the entire weeping tile is not possible, patch-work replacements of sections of the tile could be completed.
For a simple blockage due to a build up of soil or debris, and if there are no significant blockages or collapses in the weeping tile, a professional plumber or contractor might be able to flush the system from smaller access points, which can be dug from around the foundation walls. If the weeping tile must be replaced, installation of a clean-out port with access from the surface should be considered to allow easier maintenance in the future.
What is the weeping tile connected to?
It used to be a common practice in many Canadian communities to connect weeping tiles to a home’s sanitary sewer lateral. This allowed water to drain away from the foundation without the need for a sump-pump. However, over time, it became apparent that this practice contributed a substantial amount of water to municipal sanitary sewer systems, contributing to sewer backup problems.
Disconnecting your weeping tile from the sanitary or storm sewer can help to reduce the amount of water that enters the municipal sewer system during a heavy rainfall event. This can help reduce the chances that you and your neighbours will experience sewer backup, and can also reduce the risk of structural damage to the home.
If the weeping tile is connected to the storm sewer lateral, water can be pushed back into the weeping tile during a storm sewer surcharge. This can result in both structural damage to the home (including cracking or heaving in foundation walls and basement floors) and increased rates of infiltration flooding.
Other flood reduction options, including Option 10 and Option 12 in this handbook, can have an impact on foundation drainage. During a heavy rainfall event, or in instances where the water table is very high, a substantial amount of water can enter the weeping tile. Also, poor lot grading that directs water toward the home, backfill problems and poorly maintained eavestroughs and downspouts can increase the flow of water into the weeping tile.
Disconnection of the weeping tile from the municipal sewer system requires the installation of a sump-pit and sump-pump.
Sump-pits and sump-pumps
Water from the weeping tile should be directed to a sump-pit, and then pumped out of the sump-pit using a sump-pump. The location of the sump-pit depends on how weeping tiles are connected to the pit under the basement floor. Sump-pits are normally located where service connections enter the home (for example, where the sanitary sewer lateral enters the home).
In many cases, water from the weeping tile should be pumped to the surface of the home’s lot. If water is to be pumped onto the lot, the same precautions should be taken for the sump-pump discharge pipe as the downspout extension (Option 12):
• Ensure that the discharge point is at least 1.8 metres away from the home.
• Use a splash pad at the discharge point.
Care must be taken to ensure that this water does not affect neighbouring properties. Where lot sizes are too small or where lots cannot be graded in a manner that will keep water away from homes, a pipe may be used to carry the discharge away from neighbouring properties to municipal conveyance systems that can handle weeping tile discharge. Some municipalities may allow you to direct this water to the municipal sewer system to prevent ice build up in the winter. Talk to your municipal government to make sure that water is pumped to the right place.
Sump-pumps are usually designed to pump a low volume of water at a slow rate. While they can effectively remove water from weeping tiles, they will not be able to pump water out of the basement fast enough to prevent damage when the basement is flooding.
Sump-pumps are prone to blockage and possible failure if they are not routinely inspected and maintained. On-going maintenance will help to ensure the sump-pump will continue to operate over a long time period. A homeowner can inspect the sump-pump by pouring water into the sump-pit, and seeing whether or not the pump starts automatically. Check the manufacturer’s instructions for the pump or talk to your municipal government about proper maintenance and inspections for the pump.
Backup sump-pumps and power supplies
Most sump-pumps rely on electricity and will not operate during a power outage. It is also possible that a sump-pump could have a mechanical failure when it is most needed. If a sump-pump stops running during a storm, water from the weeping tile could flood the basement.
Backup sump-pumps and backup power supplies can help to make sure that sump-pumps operate during a power outage. Here are some backup options to consider:
- Install a backup battery powered sump-pump in the sump-pit along with the main sump-pump. The main sump-pump can be set to run when the water in the sump-pit is at a relatively low level, and the battery powered pump can be set to automatically run when the water in the sump-pit is at a higher level.
- Install a backup sump-pump that uses the municipal drinking water system for power. This unit can be connected to your home drinking water system, and as long as there is water pressure in your home, this type of sump-pump will continue to operate. As with the battery powered backup pump, this type of pump may be installed in the same sump-pit as the main sump-pump.
- Consider installing a generator to provide backup power. A generator must be specially wired into your home’s electrical system and must be located outside of the home. Generators may use propane, diesel or gasoline for fuel. Some generators can be connected to the home’s natural gas connection, ensuring that it will not run out of fuel when it is running for extended periods. The backup generator system can also be used to power other electronic appliances in your home, for example, fridges and freezers.
If you are thinking about installing a backup generator, you should thoroughly review your options. Talk to your municipal government, your electric utility provider and a licensed electrician about this option. The generator should be installed in a manner that is consistent with relevant electrical codes in your area and all relevant building and electrical permits should be attained before you proceed with this work.
Option 15: Mainline, normally open backwater valve
After a thorough plumbing inspection by a qualified professional has been completed, and after you have talked to your municipal government about appropriate actions you can take to reduce basement flooding in your neighbourhood, you can consider installing a backwater valve. Mainline backwater valves are placed directly into the sewer lateral at the foot of your basement wall, and serve to reduce the risk of sewer backup in your home.
The proper installation of a mainline backwater valve can be complicated. In an existing home, installation will require breaking up the concrete basement floor and cutting a section out of the sanitary sewer lateral. You will need the assistance of a licensed plumber to install a mainline backwater valve. Talk to your municipal government to see if they have a list of pre-approved plumbers who can install backwater valves.
Like any other part of the home, backwater valves require periodic maintenance to ensure proper performance over time. An improperly maintained valve may fail during a flood event. Most mainline backwater valves come with a see-through top so that you can check to see if it is clogged with debris. The valve should be checked regularly to ensure that it will function properly when it is needed. You will likely need the help of a qualified plumber to carry out maintenance of the valve.
In order to drain your foundation drain when the backwater valve is closed, you should also disconnect your weeping tile from the sanitary sewer, which will require the installation of a sump-pump and sump-pit (see Option 14). If weeping tiles are connected to the sanitary lateral, weeping tile drainage may backup into the basement when the backwater valve is closed, as this water will have no other way out of the home. Disconnecting the weeping tile from the sanitary sewer lateral will also reduce the chances that water will backup into the weeping tile and cause structural damage and infiltration flooding in the home.
For proper operation of the backwater valve, sewer cleanout ports must be properly capped and sealed. The placement of the sewer
cleanout relative to the backwater valve will vary depending on the nature of the home’s plumbing system.
Option 16: Maintain your sewer laterals
Sewer laterals, which connect a home’s plumbing system to the municipal underground sewer system, should be regularly maintained. Over time, cracks in sewer laterals can emerge from tree roots and shifting soil. Cracks can allow groundwater into your lateral, which can increase stress on the municipal sanitary sewer system, thereby increasing the chances of sewer backup. As well, loose joints where laterals are connected to home plumbing or the municipal sewer system can increase the risk of sewer backup.
Over time, the sanitary sewer lateral may also become clogged with fats, oils and grease (FOGS) or other debris, which can restrict flows and cause sewer backup (see Option 5). This may especially be a problem in older homes when the lateral has not been routinely maintained. Sewer laterals are accessed through the cleanout port, which may be located either inside of the basement or outside of the home, close to where the lateral enters the home.
To find out how well your sanitary sewer lateral has been maintained, you should talk to a licensed plumber who can carry out an assessment of your lateral.
Option 17: If you have a storm sewer connection, consider severing it as close to the municipal sewer system as possible
Sewer backup can occur not only when the municipal sanitary sewer system surcharges, but also when the municipal storm sewer system surcharges. A surcharging storm sewer can force water back into home storm sewer lateral connections. This water can then exfiltrate from (or be forced out of) storm sewer laterals. If the storm sewer lateral and the sanitary sewer lateral are close together, water that has exfiltrated from the storm sewer lateral can enter the sanitary sewer lateral and cause sewer backup in the home.
The storm sewer lateral should be severed as close to the municipal storm sewer as possible. This will reduce the chances that water will exfiltrate from the storm sewer lateral into the sanitary sewer lateral, thereby reducing the risk of sewer backup.
In some homes, weeping tiles may also be connected to the storm sewer lateral. If the weeping tiles are connected to the storm sewer lateral, a sump-pit and sump-pump should be installed to direct foundation drainage to the lot’s surface to allow for proper foundation drainage after the storm sewer lateral is severed (see Option 14).
High amounts of exfiltration from storm laterals into sanitary laterals can create significant excess flows of water in sanitary sewer systems. These excess flows can increase the risk of sewer backup for everyone in a neighbourhood. If a large group of homeowners sever storm sewer laterals that are subject to exfiltration, sewer backup risk can be reduced for everyone in the neighbourhood.
You will need permits from your municipal government and the assistance of professionals to sever your storm sewer lateral. Talk to your municipal government about this option before you consider severing your storm sewer lateral.
Option 18: Considerations for reverse sloped driveways
Reverse sloped driveways may be considered a necessity in high-density neighbourhoods, where there is no room for external garages. Reverse sloped driveways, however, create a significant flood risk as they can direct overland stormwater flows into homes. Water that enters homes through reverse sloped driveways can cause damage, and can also contribute to sewer backup problems if this water enters basement floor drains.
Catch basins are located at the bottom of reverse sloped driveways to drain water to the municipal storm sewer system. When there is a surcharge in the municipal storm sewer system, stormwater can be forced back into catch basins, where it will then flow into basements, garages and weeping tiles. Your municipality may recommend installing backwater valves into reverse sloped driveway catch basins to reduce stormwater backup.
As this type of backwater valve is located outside of the home, it is susceptible to blockages from debris and ice, and will require periodic inspections and maintenance. If downspouts or weeping tiles are connected to catch basins, they should be disconnected before a backwater valve is installed. Talk to your municipal government to see if they recommend this option, and ask for information on proper installation of this type of backwater valve.
Ensuring that reverse sloped driveways do not have a constant slope into the home from the street can also reduce the chances that water will enter the home. A 15 cm high-point between the surface of the street and the point where the reverse-sloped driveway begins to slope down toward the home can reduce the chances that overland flooding will enter the home through the reverse sloped driveway.
In some cases, the reversed sloped driveway catch basin may be connected into the home’s weeping tile system or sanitary sewer lateral, which would increase sewer backup risk for both the home and the neighbourhood. If the catch basin is connected to the sanitary sewer, talk to your municipal government about connecting it to the proper municipal sewer system. Identification of which municipal sewer system sloped driveway catch basins are connected to should be part of the detailed plumbing investigation of the home (see Option 3).
Option 19: Window wells and window well covers
Window wells can help improve drainage around your basement windows. Improved drainage can help to prevent water from entering your basement, and can also reduce dampness in your home. Window wells can also help to prevent rotting of window sills, which may compromise the ability of your windows to hold back flood water.
Window wells should be installed around all windows that are close to or below the lot’s surface. The outer edges of the window well should fit snugly against the foundation wall, and the bottom of the well should be a least 15 cm below the underside of the window. A mixture of coarse material such as gravel and soil should be placed in the well. Below ground window wells must be drained, otherwise they will fill up like a tub and pour through the seal of the window into the basement. Therefore, window wells normally drain into the weeping tile under the home.
The direct linkage from the surface to the foundation drain can cause overloading of the weeping tiles and increase the chances that water will enter the basement. Therefore, proper lot grading to shed overland water away from window wells and building walls is essential (see Option 13). Additionally, if there is the potential for a large volume of roof water to overflow the eavestroughs and spill directly into the window well, or if large amounts of rain can fall in the well, a window well cover should be installed to divert this rainwater away from the window and house. In this way, the window well cover can reduce the chances that water will enter the basement through the window, and will reduce the amount of water that enters the foundation drainage system.
Option 20: Avoid finishing basements and storing expensive, valuable or irreplaceable items in your basement
All types of basement flooding, including infiltration, overland and sewer backup flooding, can lead to considerable damages to the home and property within the home. Even if municipal governments and private homeowners have taken all reasonable actions to reduce basement flooding, there will always be a chance that basement flooding will occur.
Insurance companies and municipal governments have begun to recognize that one of the main culprits for damages in basement flooding events is the use of finished basements as additional living spaces. When flooding happens in a finished basement, damages can be very significant because of damages to carpeting and floor coverings, drywall and wall coverings, not to mention damage to home theatre equipment and furniture.
In many cases, damages caused by basement flooding are not eligible for insurance coverage, especially those caused by overland flooding and infiltration flooding.
If your basement is subject to infiltration, overland or sewer backup flooding, consider leaving it unfinished and only using it for limited storage. This may be the best way to prevent severe damages when the basement floods.
This handbook also provides some background information and descriptions of municipal sewer and stormwater management issues that have led to basement flooding problems. It is our hope that this handbook will provide useful guidance to any homeowner who would like to reduce their chances of having basement flooding.