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Plumbing/drain question

jimy

Well-known member
Joined
Mar 25, 2015
Messages
157
I would like to add a sink in the finished part of my basement. The picture below is of the unfinished side which has the plumbing exposed. The sink will be opposite side of the sink shown. The pipes drain to the right. The 90 degree fitting at the left goes to the finished side and then up to the master bathroom. The basement has an exposed french drain on the perimeter. (the finished part of the basement is an addition - that is why you see the exposed french drain there. The horizontal main pipe is 24" above the floor.

1 - You can see a cast iron pipe/cleanout that feeds from the open french drain and under the concrete. Is this some sort of air vent for under the floor? Wouldn't this back sewage to under the floor if something downstream plugged?

2 - I known water goes downhill, but how much higher than the main horizontal pipe should be sink drain be to keep the master bath drain from filling into the sink? And I would want the sink drain to no go down the vent pipe.

The sink is just for occasional use so it can be higher than normal. Or I'm ok with putting a pump in if that is better.

Jim
 

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firebirdparts

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Joined
Jun 8, 2016
Messages
10,608
Location
Kingsport, TN
I'm a chemical engineer, so let me give you a fundamentalist answer: There is no amount of elevation in the basement that will be adequate to keep water from backing up when the water is coming from upstairs. However, there's also no additional height required if the sewer just drains like it's supposed to.

What happens in real life is that the elevation you mount the sink will dictate the amount of clogging that causes you to call the roto-rooter man. It's an equilibrium sort of thing. Mount it lower, you'll call him sooner. If it doesn't clog, then you'll never call.
 
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greenskeeper

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Joined
Dec 7, 2018
Messages
650
Location
PA
odd looking setup

under 2.5" pipe you need at least 1/4" drop per foot, and a vent no further than 8' unless you use a cheater vent

so the sink should be above those figures in height, standard is 29-36" depending on style/preference
 

stokefire7

Well-known member
Joined
Oct 5, 2011
Messages
616
That 2" contraption with the return bend is useless and unnecessary. You can use that horizontal branch for a trap arm( it's about the right height for a laundry tub).
 
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