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Greywater system: p-traps and vent?

Trevor_Lambert | Posted in General Questions on

In my new workshop I’m going to have a floor drain for car runoff and a utility sink. The drain will run through a filter bag to a drain basin outside the building. I originally imagined installing p-traps and vents, but now I’m thinking it’s not necessary. Not having to concern myself over trap arm length would certainly make the floor drain installation much less complicated.

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  1. kentthompson | | #1

    Hello Trevor,

    I used to install greywater systems. It's true that a p trap and vent aren't quite as critical if you're not connecting to a source of sewer gas. The other reason a p trap helps is it's another barrier to creepy crawlies coming up from your drain basin.

    Here's a link to some more information:

    I'd discourage using a filter're better off having everything flow to the basin. The filter bag will end up being a maintenance item you won't look forward to.

    1. Trevor_Lambert | | #2

      Maybe I'll have p-traps, but I won't worry about the vent for the floor drain. Most of the time it's just going to be a trickle, and in the rare case of putting enough water down it to empty the trap I can just manually fill it.

    2. Trevor_Lambert | | #3

      Reading that link made me realize what I'm doing isn't really a grey water system. I'm not trying to capture waste water for any purpose, mostly just directing water that would normally drain out the garage door and route it under the floor. The utility sink is basically just to capture splashes from filling vessels, or other essentially clean water that I just want to go outside.

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