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Question DetailsAsked on 7/13/2016

What kind of check valve do i need if my basement floods and it comes out of shower and floor drain

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If this happens ONLY when water is being run, toilet flushed, washer emptying (usually the first cause noticed), etc, then you have a partial blockage in the sewer line and you need it routed/jetted out by a Sewer and Drain Cleaning contractor or a Plumber who does routing of sewer lines. IF on septic, can also be due to overfill of septic tank or saturated leach field causing backup.

See other comments on blocked lines in the Home > Sewer Cleaning link in Browse Projects about jetting versus routing and the reasons for having the blockage chased and cleaned all the way to the septic tank or street (as applicable) to avoid another blockage in the immediate future.

If this happens when there is NOT water running down drains in the house, then is probably associated with significant rain storms or high water conditions in local waterways, because your sewer line is backing up from overfull street sewers or leach field, as applicable to your case. You could check with sewer utility (if on public sewer) regarding whether this is common in your area or possibly indicates a blockage in their lines that thye will clear. Neighbors should also be able to tell you if they have this happen or have a backflow prevention device or lift pump in their basement.

In this sort of case, if a repeating event during high water conditions locally, you have four common possible solutions - different ones are best used in different situations and it depends largely on your comfort level with a system that might fail on you when out of the house, on the frequency of this sort of event, and of course cost.

1) simplest is commonly to put in a manually-operated shutoff valve on the basement sewer line IF it is a separate branch that can be shut off without shutting off the upstairs line(s). In this case, you would have to manually close the valve during risk periods AND hang DO NOT USE signs on all the basement water sources so no one uses any basement water and causes flooding. Commonly $250-700 range depending on whether the line can readily be tapped or if concrete has to be dug up to get to the line. Of course, forget to open and basement drains will not drain out - forget to close afterwards (a lot more common) and there is no backflow prevention. If you go this route, put a LARGE obvious sign on basement door or other obvious place indicating when it has been opened. For this application, closed would be the normal mode - open onlhy when using downstairs water sources.

2) next simplest, similar cost (about $250-700 typically depending on ease of access to the line and where you are willing to put the valve) is a sewer backflow check valve - works like this -

- which is an in-line flapper valve that is supposed to only allow outflow and shut off when inflow (reverse flow) starts in the sewer line. Commonly leak a small amount at times and can stick all the way open without warning, so the risk of a backflow event like you are having now still exists with this type of valve. As you can tell, I do not trust them.

3) more expensive (over $500 certainly and possibly pushing $750-1200) is an electric backflow prevention valve - like above but senses backflow and electrically shuts a valve. Less likely to leak or stick open though small leaks due to grit and paper getting caught in the valve can occur, so you commonly have to run water in each basement drain every few days to clean it out and clear accumulated liquid in the pipes to be sure to avoid a backup. Unless battery-backup is provided will not work when there is a power outage - like major thunderstorm or tornado which commonly also is when this type of flooding occurs, so a significant drawback there. A more sophisticated type measures buildup of pressure from the inflow side and only opens it when there is water coming down the line from inside the house - which minimizes the backflow issue but if it fails means your basement shower/basin stop draining. More on $1000-1600 range commonly.

4) final comon alternative is a septic lift pump - a pump with enclosed tank that the basement drains flow into, and it pumps the liquid up to or above the ground floor (above the highest possible outside pipe fluid level, which is generally septic tank or street manhole elevation) into the sewer line there, so above the level that the water is trying to back up to in the sewer lines. Certainly $1500 plus and commonly more in the $2000 range by the time done unless the sewer lines are all exposed - and requires that the upstairs sewer line not flow through the basement connecting to the basement drains (which it might if they are not on a separate branch line) - has to flow direct to septic tank/street from the upstairs lines. So sometimes the upstairs line has to be cut and rerouted direct to the outside, the connection to the basement plugged off, connection to basement line capped in basement (and possibly a new vent line run in some cases), then the lift pump cut into the basement line and routed upstairs, and the old basement line to outside dug up and capped off or routed out of service by replacing a wye with a straight-through piece or elbow at that connection to avoid future blockages. Bad idea to abandon a sewer line in-place connected to an active one - can back up into the unused line and form a heavy sludge and paper blockage that can "grow" out into the active line and block it. If an incoming branch is going to be abandoned in-place, put a cleanout at the point it is being cut out of the system so the old abandoned section can be routed out if needed in the future. Leaving that old unused branch in service can also result (especially with metal pipe) in a lot quicker corrosion failure and leakage of that section because it will go totally anaerobic, causing corrosive sulfur bacteria and corrosion products to flourish.

Answered 3 years ago by LCD

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