Let’s begin with a brief introductory exercise to become familiar with flood proofing terms. See if you can match the following descriptions with the numbers on the illustration (answers are at the end of the glossary):
Even after a few short years, you can see where the soil has settled, but may not be able to see depressions hidden by decks, stairs or patios. During rains, low areas become puddles next to the foundation.
To combat this problem, clay soil is recommended as a cap for the backfill zone (shown in the illustration). Top soils or sandy soil are not recommended. They allow water to percolate down into the backfill zone. But if you want a flower bed around the perimeter of the foundation, start with a clay base 8 - 10 inches thick. Slope the clay so that water will drain away from the house. Extend the clay 6 - 8 feet out from the house. Decorative landscaping materials or a flower bed may then be added.Our heavy clay soil contributes to basement flooding in two ways. First, by blocking the flow of water away from the backfill zone and second, by swelling and cracking concrete walls and floor. Water trapped between the basement wall and the undisturbed clay soil may eventually seep through the basement wall. Or, as the clay soil gets wet and swells and then dries, powerful forces crack basement walls and floors. The following example explains this concept.
Referring to the first frame of the illustration, we see a large hole or excavation much like a swimming pool. When filled with water, the undisturbed clay soil swells and expands, creating a barrier that could retain water for weeks.
If, instead of digging a swimming pool we were to excavate a new basement, the same reasoning would apply. Any water percolating into the soil on the outside of the walls would remain trapped within the backfill zone as shown in the second frame. With time, rainwater or snow melt could soak into the backfill zone.
The third frame of the illustration shows unwanted water in the backfill zone. Powerful pressures from swelling and shrinking clay soil crack the concrete walls and floor. Cracks become pathways for water to enter the basement.
So we see that water entering the backfill zone either seeps into the basement or enters through cracks in the concrete.
Preventing water from entering the backfill zone is the answer.
Eavestroughs catch rainwater and downspouts carry water from the rooftop to the ground. Downspouts that are too short will pour rain water directly into the backfill zone as shown below. Soil erosion and water in the backfill zone are consequences of short downspouts.
But what if rainwater does enter the backfill zone? Where will it go? How can it be disposed of to avoid structural or in-basement property damage? The modern answer is a foundation drain or weeping tile system.
Rainwater entering weeping tile varies from house to house. Weeping tile flow ranges from a few teaspoons to hundreds of gallons per day. Strongest flows usually happen during spring melt or from a long rainstorm.
To help you visualize your foundation drain, consider the following step-by-step description for new home installation of weeping tile. Illustrations correspond with each step. The illustration enclosed in the circle (on left) is a magnified view from the bottom edge of the excavation. The illustration on the right is the excavation or site where the basement will be built.
1. A backhoe (large earth moving equipment) is used to dig a hole for the basement to rest in. The size of the hole or excavation should be as small as practically possible, yet allow room for work crews. The base of the excavation is to be as flat as possible.
Examine the illustration which shows House A. Note water percolating through the backfill zone to the weeping tile, sump pit and finally into the domestic sewer. Rainwater has taken up space in the underground sewer pipe. That space was meant for sewage, not rainwater. When the pipe is over filled like this, it is called sewer surcharge.
Combating sewer surcharge may involve some or all of the following in-basement actions: installation of a sump pump, installation of a backflow valve and permanent disconnection of weeping tile water from the domestic sewer.
Equally important are actions that can be taken in the yard. Sloping soil from the foundation will drain rainwater and snow melt away from your basement. Checking and cleaning eaves and downspouts will ensure they discharge properly to a splash pad.
Each year in Edmonton, thousands of gallons of clean rain and snow melt enter the domestic sewer unnecessarily. Rainwater or snow melt is transported to and processed at the sewage treatment plant. Instead, it could be pumped from sump pits onto streets where it would run off into a storm sewer and then to the North Saskatchewan River.
|Pump weeping tile water out of your basement onto your yard. While there are other options, a properly installed sump pump is a positive step to reducing the risk of sewer backup in your home and other homes in Edmonton.|
Whichever approach you decide to adopt, the more effort taken to diagnose basement flooding problems, the lower the cost and the better the solution.
The next section introduces ways to diagnose basement flooding problems. Before moving into this section we discuss briefly how to locate your sump pit. It is really the starting place when flood proofing.
Once you find the sump pit, you can check for several things:
If you thread-in the P-trap cap during a storm, bear in mind that the weeping tile will continue to flow. You will need to check the sump pit water level frequently to ensure it doesn’t overflow.
A sump pump will start automatically. Save yourself a sleepless night of bailing. Install a sump pump now!
|Remember, weeping tile water is just water
that has made its way through the soil into the sump pit. A properly
functioning sump pit includes a sump pump that will move weeping tile
water outside the house, where it can drain from your yard into the
storm sewer. In so doing, rain or snow melt is not overloading the
domestic sewer and contributing to the flooding of someone else’s
|1.Problem:||Water entering at the basement walls
and concrete floor
|Symptom:||Wet carpets and floors along basement walls.|
|Downspouts are too short and water is percolating through
the backfill zone.
|Solution #1:||Extend downspouts so that they discharge rainwater at least six feet from the foundation onto a splash pad.|
|Solution #2:||Position a rain barrel so that it will catch rooftop water. Be sure to have an overflow spout so that water is discharged away from the foundation as described above.|
|Downspouts and/or eavestroughs are clogged and rainwater
is spilling onto the ground around the foundation and percolating into
the backfill zone.
|Solution #1:||Clean and leak proof eaves and downspouts each spring.|
|Solution #2:||If your eaves are clean and working well, yet water is still spilling over, there may be another problem. If the underground yard pipe is buried, it may have become blocked with roof debris. Disconnect your downspout the next time it rains. If there is a sudden, strong, steady flow that quickly slows after a few minutes, the underground yard pipe is plugged. You may wish to redirect the downspout to the surface. This will require adding an extension and splash pad.|
|Low spots on the backfill zone are allowing water to pool
next to the foundation.
|Solution #3:||Add soil over the backfill zone, sloping it away from the foundation. Remember to pay special attention to areas under decks, steps and other covered or hidden areas. Often, these areas are neglected yet contribute to wet basements.|
|General Comments:||Clogged downspouts and low areas next to homes commonly contribute to basement flooding in Edmonton. They may require attention every few years. Routine maintenance, combined with sound flood proofing practices, will keep water out of your basement.|
|2.Problem:||Water entering the basement from under
the basement floor from the sump pit (no sump pump is installed as shown
|Symptom:||Water flowing from sump pit onto basement floor or heaving basement floor.|
|Water being collected by the weeping tile is accumulating
in the sump pit with P-trap cap in place as shown on the previous page.
|Solution #1:||Remove the P-trap cap to drain water from the sump pit into the domestic sewer.|
|Solution #2:||If you are unable to remove the P-trap cap and weeping tile water is filling the sump pit, handbailing is another way to dispose of the rainwater.|
|Solution #3:||Install a proper sump pump to move water outside the house and away from the foundation, as shown below. This is the recommended solution.|
|If the domestic sewer is surcharged, you risk sewer backup by removing the P-trap cap.|
|General||As a rule, P-trap caps should not be threaded into place unless your home is equipped with a properly functioning sump pump. Homeowners who have a properly functioning sump pump, P-traps in place, and close off any floor drains during and after storms can expect to have a high measure of flood protection.|
|3.Problem:||Water enters the basement from the sump
pit (sump pump in place).
|Symptom:||Water flowing onto the basement floor out of the sump pit.|
|The sump pump has failed.
|Solution:||Should you want to service the sump pump yourself, the
following is a list of things to check:
Another option is opening the P-trap by removing the cap. Remember, if the sewer is surcharged, there is a risk of sewer backup in addition to the weeping tile flooding.
|Exercise extreme care when around the sump pump, your contractor will be working with electricity near water. Have your consultant insure that the contractor follow the instruction manual supplied with the sump pump.|
|General Discussion:||Sump pumps contain parts that may be continually submersed in water. Rust and small soil particles can damage the pump. Regular inspection is important. Servicing the sump pump every few years will ensure it is ready to function when needed.|
|4.Problem:||Sewer backup entering at basement floor
|Symptom:||Sewage flowing from floor drains and basement plumbing such as toilets, showers and washing machine standpipes.|
|Too much storm water or snow melt in the domestic sewer
is causing the sewer to back up.
|Solution #1:||Thread in all basement floor drain caps, including the P-trap. Also, close the gate valve. This is usually a large, red handled valve. Sometimes it is recessed in the floor. In developed basements the gate valve is often hidden between walls or under a sink vanity. If sewage is coming out of the floor drains, close the gate valve until the flow stops. A gate valve is opened and closed manually by hand cranking. The gate valve protects only the plumbing connected to that pipe. Remember to open the gate valve after the storm has passed.|
|Solution #2:||Install a sewer backflow valve as shown in the illustration below. This prevents sewer backup from the domestic sewer, automatically preventing raw sewage from entering your home. A sump pump will automatically discharge weeping tile water from the sump pit to your yard. Not only will weeping tile water be removed from your basement but it will not contribute to overloading the sewer and potentially enter other basements. The overall impact of widespread use of sump pumps in Edmonton is a lower risk of sewer backup around the city. A sump pump and backflow valve combination offer a high level of basement flooding protection.|
|Some automatic backflow valves require venting. Discuss this with your Consultant.|
|5.Problem:||Your sump pump operates continually,
but doesn’t move much water.
|Symptom:||Only small volumes of water are pumped and the sump pit water level hardly drops; but the sump pump works constantly.|
|No check valve is in the sump pump discharge pipe.
Without a check valve, water flows back down the discharge pipe into the
sump pit, partially refilling it and initiating another pump cycle.
|Solution:||Inspect the sump pump to see if there is a check valve in the pipe. Check valves can be located just above the sump pump or near the basement ceiling where the pipe passes through the house wall. Two check valve locations are shown at points A and B on the illustration below.|
|6.Problem:||The sump pit overflows quickly during a
|Symptom:||Water flowing onto the basement floor from sump pit.|
|The sump pit is too small to contain the weeping tile water until the power comes on again.|
|Solution:||Enlarge the sump pit to handle a two-hour power outage.
The sump pit should have a water storage capacity of 60 gallons.
Recommended minimum dimensions are:
Hire a Qualified Consultant
Remember, you must obtain a City of Edmonton Building Permit if you intend to install a backflow valve so that the City of Edmonton can inspect the work to ensure that the job has been done according to the Plumbing Code. A permit is not required for adding a sump pump.
|1 Flooding Symptom in
||2 Probable Causes:|
are too short
|Downspouts blocked||Weeping tile water held in sump pit||Sump pump failure||Storm water overload in domestic sewer||Check valve missing||Power failure with too small sump pit||Weeping tile blocked|
|1. Wet carpet around edges of basement walls||A,B||C,D||M|
|2. Clear water overflow from sump pit or heaving basement floor||E,F,G,H||H|
|3. Clear water overflowing from sump pit (sump pump installed)||H|
|4. Sewer backup at floor drains||I,J|
|5. Continual sump pump activity||A||D||H||K|
|6. Clear water flowing onto basement floor from sump pit||A||C||E,F,G||H||E,F,L|
|7. Water ponding around house next to basement||A||C,D||N|
|3 Solutions Chart:
(Yes or No)
|A. Extend downspouts and add
|B. Install rain barrel with
overflow to splash pad
|C. Clean and leak proof eaves
|D. Disconnect downspout from
underground yard pipe
|E. Remove P-trap cap to drain sump
|F. Hand bail sump pit
|G. Install a sump pump
|H. Service sump pump
|I. Close all basement drains,
|J. Install backflow valve
|K. Install check valve or sump
pump discharge pipe
|L. Enlarge sump pit to hold 60
|M. Call professional foundation
|N. Add soil around house to drain
|Downspout extensions checked and in place|
|Grade of Property Checked (sloped away from foundation)|
|General Grade Around House|
|Under Back Step|
|Under Front Step|
|Installation Date :|
|Visual Inspection and Test:|
|Installation Date :|
|Last Time Update:|