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Home flood protection


Municipal governments prevent flooding by maintaining the sewage systems. If you
experience drainage problems, begin by ensuring that the source of flooding is not on your
property. Take steps to flood proof your home. First, learn how and why flooding occurs.

What is a Sanitary Sewer?
A sanitary sewer is a pipe, located in the street that is designed to transport wastewater
from your home. This consists of water from sanitary fixtures and floor drains inside your
house, as well as groundwater from weeping tiles around the foundation of your home.

What is a Storm Sewer?
A storm sewer is a pipe, located in the street that is designed to carry storm related water
runoff. Storm sewers are normally much larger than sanitary sewers because they are
designed to carry much larger amounts of flow.

What Causes Sewer Backup?
Extra storm-related water (from sources other than wastewater and groundwater) should
flow into the storm sewer or soak slowly into the ground without entering the sanitary

If excess storm water does enter the sanitary sewer system, it causes a supercharged
sewer flow. An eight-inch (20 cm) sanitary sewer can handle wastewater from up to 500
homes; however, it takes only a few unexpected water sources to overload this kind of

Sewer backup insurance is available on most homeowner policies for a small premium.
Check with your insurance agent or broker.

How Can a Supercharged Sanitary Sewer Cause Basement Flooding?
A supercharged sewer flows at a greater than normal level. Basement flooding can occur if
the home has sanitary fixtures or floor drains below the supercharged level.

Downspouts and Roof Drainage?
Most homes are equipped with downspouts which discharge the water collected by
eavestroughs directly into the ground. Excess water runs into the front street where it
enters the storm sewer. It is very important that this water does not enter the sanitary
sewer. If your downspout drains too close to the side of your house, this water can drain
into the sanitary sewer through the weeping tile adjacent to your house foundation.
Damage or sanitary sewer surcharging can occur if rainwater drains too close to your
house on ground that may not be tightly compacted. The excavation for your basement
may have been dug a few feet wider on all sides to allow working room during construction
of the basement walls. When this extra space was backfilled, the soil may not have been
tamped down as tightly as the original soil, making it more likely to settle and trap surface
Surface water soaking down to your foundation can create problems: it can damage your
foundation; seep through cracks in your basement wall, causing dampness; or overload the
sanitary sewer by draining through weeping tiles, causing a sewer backup.
What You Can Do to Prevent Flooding:

  • Fill in any settlement next to your house.
  • Redirect storm water away from your house.
  • Make sure the ground slopes away from your house on all sides.
  • Always keep your downspout extension in place.
  • Check to see that your downspout extension drains a good distance away from your
    house in an area that will not erode.
  • Be careful that water does not drain into your neighbour’s property.
  • If your downspout is connected to the weeping tile adjacent to your home, disconnect it
  • If you are constructing a new home and plan to build on a slab, or install a washroom in the basement, consider taking the necessary precautions to prevent sewage and water from backing up into your house through the sanitary drains.
  •  You may also consider taking these precautions in an existing home, but these changes
    vary in complexity and cost.
  • You may be able to do some “floodproofing” tasks yourself, while other changes need a
    qualified contractor or tradesman.
  • One aspect of flood protection involves the installation of backflow valves on toilets, floor drains, washing machine drains, rain downspouts, sump pumps and any sink drains in the basement. Main sewer lines and septic connections should also be considered. These are designed to prevent sewage and water from backing up through these waste lines. Some backflow valves operate automatically while others may have to be closed by hand.
  • In most cases the backflow valves may need to be installed by a qualified plumber or
    contractor according to existing building codes. Be sure you understand the type of
    backflow valves installed, including their operation and maintenance.
  • Your municipal office can advise on floodproofing in your geographic location.

Sewer Backup Protection Can Help

  • Talkto a qualified plumber before you install any sewer backup protection devices. Plumbing fixtures such as toilets, sinks, showers, floor drains and washing machines that are set below ground level require special protection from sewer backup. Read about the following devices and decide if they can help you.
    •  Screw Cap. If you’re having trouble with your floor drains, a screw cap installed upstream of the trap seal of the floor drain may be all you require.
    • A Canadian Standards Approval (CSA) Inline Sewer Backwater Valve should prevent sewer backup if you maintain it properly and have it checked regularly. Your plumber can provide you details on maintenance.
    • A Gate Valve. Where a backwater valve isn’t sufficient protection, you may need a gate valve and a backwater valve for basement plumbing fixtures that are subject to backflow.  Sewer Backup Insurance. This insurance is available on most policies for a small premium. Check with your insurance agent or broker.

Take special note of the preparations you must take to protect your home and major electrical and gas-fired appliances.

  • Seal hazardous materials such as weed killers and insecticides in plastic garbage
    possessions from the basement to an upper floor. bags, and move them into safe storage or dispose of them safely

Electrical Appliances

  • At the first warning turn off electrical power and leave it off. If the basement is already
    wet, be cautious. If you are confident that you can do it safely, stand on a dry wooden
    chair or box and use a dry board or stick to turn off the main switch.
  •  Water usually ruins electrical motors. Move all portable electric heaters, power tools and electrical appliances to a safe place.
  • If this isn’t possible, and if you are qualified to do so, consider removing the motors,
    controls and switches from furnaces, refrigerators and washers.
  •  If you can, consider moving all thermally insulated appliances such as freezers and
    refrigerators to upper floors of the house. This precaution should save you the expense of replacing insulation if it gets wet.

Gas-fired Appliances

  • At the first warning of flooding, turn off all gas-fired appliances and put out the pilot light.  Then turn off the gas inlet valve to your home, which is located at the gas meter. This will prevent gas from escaping when the inlet valve is re-opened, in the event that any burner controls had been accidentally been left open.
  • Do not remove any gas-fired appliances without ensuring that the main gas inlet valve
    has been closed.
    There should be no smoking or open flames of any kind in the area. To avoid causing
    sparks, use a flashlight taped in the “on” position.
  • For a forced air furnace, move the fan motor and fan to a dry storage place if possible.
  • Do not drain the hot water tank — it will serve as ballast to secure the tank in place.
    If gas appliances are removed, the gas outlets should be made tight by means of a
    plugged valve, a cap, or a plug on the piping system.

Remove any basement toilet bowls. Plug these outlets and all other basement outlets,
such as floor drains, sinks, laundry drains, etc., to prevent floodwater from entering them.

Emergency Management Alberta

sump pump design criteria

For more information, download the Basement Flood Handbook.