Backwater valve
backflow prevention device
A backwater valve is a backflow prevention device used to prevent outbound water through a dwelling's drain pipes from re-entering -- "back flowing"—into a home. The valve contains a flap that allows water to exit the home, but closes to prevent the back flow into the home.
Backwater valves commonly activate when a city's sewer lines are unable to handle a large amount of falling precipitation; this puts homes that are tied into the storm lines at risk of having water back flow into them.
There is a big difference between backwater valves and backflow preventers:
A backwater valve prevents raw sewage from backing up into your home through your toilets, showers, etc.
A backflow preventer deals with protecting a potable water source from being contaminated by a reverse flow of foul water (ex: isolating your toilet's flush cistern and water supply from the toilet bowl water itself).
This brief starts where responsible research should: with the source description of “Backwater valve” as backflow prevention device. Everything that follows is an evidence route, not borrowed authority.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Apr 9, 2025. The linked authority identifier is Q22906605. None of the 0 selected statements returned an explicit reference.
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This entry incorporates text from “Backwater valve” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.