Are S traps same as P traps?


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Old 04-18-07, 11:03 AM
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Are S traps same as P traps?

I want to raise up a bathtub's P trap to between the floor joists, but obviously the following DWV must be just below the floor joists. If I raise up the trap, then add two elbows to lower the line down to the straight DWV run, then the result would effectively be an S trap. Would this still work? I don't see why not, but I may be missing something.

You can assume the p trap that exists is properly vented and resultantly the vent would come after the created S trap.
 
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Old 04-18-07, 01:47 PM
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Looks like S traps are a no-no according to Illinois...

http://www.ilga.gov/commission/jcar/admincode/077/07700890ZZ9996deR.html

Comments still accepted...
 
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Old 04-18-07, 02:00 PM
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The S trap they showed is a one piece trap. The traps you would find under a sink now(new install) are in 3 different pieces. They should be legal in your area. Check with your local inspector. A P trap is also showed on that page. A p-trap is in 2 different pieces, with nothing else joining it, which is legal.
 
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Old 04-18-07, 04:28 PM
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So curious what is hang up on one piece models? Difficult to clean out?

Yeah I don't see what the issue is with S trap-- once it makes it to the apex of the second peak it falls down to the main run, rather than falling away at the gradual slope taht would be at the exit of the "P".
 
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Old 04-18-07, 07:39 PM
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Scratch my previous post... looks like suction causes S traps to fail. What would multi-piece or single piece have to do with it? It seems to be suction issue.
 
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Old 04-18-07, 07:49 PM
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I guess my previous post didn't make it.

Yes, S traps are not allowed for "suction" reasons. An S trap is prone to siphoning and that removes the seal.
 
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Old 04-18-07, 10:12 PM
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I have a vent right at the outlet of the S trap so I think I'm going to go for it.

Should be analogous to the exit of a kitchen sink P trap heading into the wall with a wye to a vent right there in the wall.
 
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Old 04-19-07, 09:48 AM
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S-traps

Your call, when you start to smell sewer gas in your install you will realize why s-traps are against code!!
 
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Old 04-21-07, 08:42 AM
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Shacko-

How will my trap water get sucked dry with a vent at the top of the last turn?
 
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Old 04-21-07, 09:18 AM
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S-traps

S-traps drain too fast, this is the reason that they are not permitted under most codes, they drain so good that there is not enough water left to make the seal. A vent near the trap just increases this suction. Still your call.

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