Apologies if I missed this as I searched topics.
Question: when we find an S-Trap under a sink vanity where the drain pipe exits through the floor of the vanity (and the actual floor), how can that be corrected by replacing with a P-Trap? Sorry if I’m slow on the uptake. Does a certain length of horizontal pipe need to be added (from the newly installed P-Trap) and THEN have it drain to original drain exit spot in the floor of the vanity?
Needs to reach some venting before heading down so extending the trap arm won’t help. Most jurisdictions allow AAVs (air-admittance valves) which can be a lot easier than reaching venting.
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If you look at the illustration the vertical pipe behind the wall in the second picture is also in place in the s trap version. It is usually located in the corner of the room and the sink will have a pipe in the floor going horizontally over it.
Changing he s trap to the p trap can be a real pain depending on the floor and wall layout. You can point it out, but I grew up in an old farm house and we had those s traps everywhere (once indoor plumbing was added) nary a problem.
The change had to do with the possibilty of sucking the s trap dry with a large volume of water.
While you are looking at the plumbing, since these s traps appear in older homes, be aware that galvanized pipe will often accompany these arrangements (depending on age). Galvanized plumbing will drain fine until it doesn’t and no amount of roto rooter will unclog it. (been there done that).
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Though this job is pretty crappy, it does illustrate Matt’s point. (I think the AAV is a little low. There is no way to disassemble it for maintenance. Pipe dope on the AAV joint? Strainer connection?)
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Did you call out the galvanized pipe?
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Thank you, Matt.
Required minimum 4 inches above the horizontal branch run…
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