Renovation & Design

ASK THE INSPECTOR: Sump pump, backflow valve in older home


QUESTION: With all the dire warnings in the news these days about the prospect of a flood this spring, I have been exploring our options regarding installing a sump pump and back-flow valve.

Our house is about 55 years old and has never had this equipment and has never had a flood problem, but I guess there is always a first time. Most of the things I have read about back-flow valves say they should be installed where the sewer enters the basement. One plumber I contacted says it's better to just put the valve on the sewer line that runs from the bathroom in the basement. He explained this would prevent sewage backup into the basement and still allow us to use the upstairs bathroom.

What do you think of his way of doing things? The price is approximately the same. Also, what kind of annual maintenance am I supposed to do on these pieces of equipment?

-- Louise Gillman

ANSWER: Installation of a backwater valve in your older home can prevent sewage from entering your home if the municipal sewers back up, but should be installed along with a sump pit and pump. The proper configuration and maintenance is very important for proper function of this system, which will be critical, but only when needed.

An in-line backwater valve is simply a one-way valve installed in your main sewer line below the basement floor slab. This valve allows water and waste to flow out towards the street sewer, but not the other way. If the flow begins to reverse itself, normally only during a major sewer backup or blockage, the valve shuts. This prevents the liquid sewage from backing up into the pipes below your floor and coming into your home through the floor drain and basement plumbing fixtures. The problem with this system is when it's operational, water and waste cannot leave the building either.

Most sewer backups occur when there is a large amount of rainfall, normally during heavy summer thunderstorms. During these storms, the weeping tiles around your foundation may be collecting large amounts of rainwater that has filtered through the soil around your home. In older homes like yours, these weeping tiles terminate in the catch basin, which empties the water into the drain below your basement floor.

If there is a backwater valve installed on your outgoing drain and it shuts due to backup, this rainwater has nowhere to go. In that case it will quickly begin to back up and flood your basement. That is why a sump pit and pump are needed. An overflow pipe should be installed between the top of the catch basin and the sump pit that allows this excess rainwater to drain by gravity to the sump. Once the water flows into the sump pit, the pump should engage and pump this water to the exterior of the home, where it will be harmless.

I'm not sure of your plumber's reasoning, unless he recommended installing the backwater valve in the drain protecting your basement bathroom in combination with a simple backup valve in the bottom of the catch basin. Floor drain backup valves are inexpensive, pressure-fitting devices that you install in the bottom of the catch basin. These normally have a rubber ball attached to the bottom of a metal rod, which is forced up into the body of the valve if the water level in the drain rises, blocking passage of any liquids.

If this device is installed, along with a proper backwater valve and sump pump, it should still provide adequate protection from basement flooding, unless you have separate basement laundry drains that would also be unprotected. This method may allow you to use your upstairs bathrooms during a sewer backup, but that would be very temporary. If you drained too much water too quickly, it could back up through your main floor fixtures.

My main concern with his suggestion is you will have two devices to inspect and maintain, and the cheap floor-drain devices have been known to deteriorate after several years, requiring replacement.

Maintenance of in-line backwater valves should be minimal, but sump pumps should be inspected and tested at least once a year. This testing is quite easy and can be accomplished by partially filling the sump with water, or by reaching into the pit and lifting the float switch attached to the pump. Some pumps also have a small pressure-switch testing hose extending from the plug that requires a few seconds of blowing or sucking before plugging back in to turn on the pump. If the pump does not operate when tested, it may have become corroded or seized and should be immediately replaced.

It is absolutely critical to test the pump regularly because it may never come on unless there is a backup event. If it is damaged or non-functional when needed, it will provide no protection from your basement filling with water.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the president of the Canadian Association of Home & Property Inspectors -- Manitoba ( Questions can be emailed to the address below. Ari can be reached at (204) 291-5358 or check out his website at


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