The way the 2" rough in went we ended up with a trap of sorts then a pipe to where the tub trap will be. Not completed yet.
Just wondering if a tub trap and a trap made with the rough in piping will cause some sort of problem. The rough in trap was made off a 4x4x2 wye. Would that be adequate as a trap by itself if there should only be one?
Thanks,
Rosharo

Here is the rule, one drain, one trap. Please explain or post a picture reagrding what you mean when you say "a trap of sorts." usually they are or are not a trap.

The fittings formed a trap. Will look at it again today but it's like if you used a 90 st down a second 90 st into that and a 45 st coming up vs a another 90 st if you were making a normal 'trap'.
Anyone know why 'one drain, one trap'? Is it because you don't need another one or is is because there is a potential problem is you do use 2.
Thanks.

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Originally Posted by rosharo

The fittings formed a trap. Will look at it again today but it's like if you used a 90 st down a second 90 st into that and a 45 st coming up vs a another 90 st if you were making a normal 'trap'.
Anyone know why 'one drain, one trap'? Is it because you don't need another one or is is because there is a potential problem is you do use 2.
Thanks.

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Anything in a drain line that bells down and holds water's a trap in the line. Double traps are illegal for the same reason as "S" traps. Because the traps aren't vented it's possible for the draining water to suction the water out of the trap allowing sewer gas to enter your home. Does this answer your question? Regards, Tom

Yes, Tom... answers it very well! The light dawns. Thanks.

If a vent is put between 2 traps it would work. But why would you even want to pay the extra expense of having the 2nd trap or installing extra venting on a single fixture drain? In Philadelphia, Pa they have curb traps with a fresh air inlet. Upstream is a main vent for the main drain of the house. One drain-one trap from fixtures are installed into the main drain.

Even though you have the second trap at the curb it has no effect on the flow because there is venting between the fixture trap and the curb trap. The drain for the fixture can not be longer than 12 feet developed length from the vented line. They do allow "S" traps in Philadelphia, but P traps are a better choice.

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They do allow "S" traps in Philadelphia,

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WRONG! "S" traps in new construction and permitted remodels are outlawed in all 50 states and Canada.
While it's possible for "S" traps to be "grandfathered in" You can't get them passed on a new job. Rule of thumb; If it has a trap it must be vented. Regards, Tom

Speedball,
According to the Philadelphia Plumbing Code P-501.2 (Prohibited traps): The use or installation of the following types of traps are prohibited: (PAGE P-17)
1. Any trap whose seal depends upon the action of movable parts.
2. Any trap with interior partitions, except when integral with vitrified clay plumbing fixtures.
3. Double traps, unless a fresh air inlet is connected to the system between the traps. (Every home has a house trap at the curb before it goes to the sewer in Philadelphia with a fresh air inlet on the top of the trap going to grade level)
4.Crown vented traps.

There is nowhere that I know in the Philadelphia Plumbing Code that says S traps are not permitted. If there is, please let me know. Every fixture that has a drain must have one fixture trap (S or P) the same size as the drain and a vent downstream. The drain can be up to a maximum of 12 feet developed length from a vented line for most fixtures except toilets or pedestal urinals. I prefer P traps myself but S traps are acceptable and approved.
Bentzle - Master Plumber

Bentzle,

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There is nowhere that I know in the Philadelphia Plumbing Code that says S traps are not permitted. If there is, please let me know.

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And by the same token show me the section that allows a "S" Trap.
Here's a few of the traps that are illegal.(see image)
Massplumber should fall under your code. What about it Mark? Cheers, Tom

Hi all:

In Massachusetts, Maine and New hampshire, Full "S" traps have been prohibited for a really long time now.

However, with that being said, and with the prohibited trap definition posted by Bentzle, it would appear that they are allowed in Philadelphia.

This doesn't surprise me too much guys. Just the other day I was talking to a plumber from another part of the country and believe it or not, that state allowed a toilet to be connected at the base of a WASTE stack WITHOUT the need to vent it!? There could be 4-6 toilets and bathrooms above this non-vented toilet and it still didn't need to be vented if it was within 6 feet of the waste stack... unbelievable!

Anyway, that definition you posted is pretty clear, Bentzle. I think we have yet another exception to the rule here. Never mind the 12' venting rule you mention Bentzle... another exception to the rules we practice by here.

Traditionally speaking, these S traps just are not good plumbing practice as they are prone to siphoning in a couple different ways. A ptrap with an individual vent is still going to be the best route. Bentzle seems to agree, too!

Have a good day all!

MARK

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Never too old to learn! Thanks Mark.
Bentzle, It seems I was in error and "S" traps are allowed in your area. Which brings up the question, Why are they outlawed everywhere else and allowed in Philly? I gave this explanation in a earlier post,

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Code addresses the worst possible scenario, and without a vent it's possible for the trap seal to be siphoned out allowing sewer gas to enter your home. Didn't say it would happen every time you drained a fixture but the possibility exists and that's enough to outlaw them.
Will "S" traps work? Yes! Back in the 40's when I broke into plumbing most of the older homes in my area had "S" traps. That's how we plumbed back then. But times changed and now they'd been outlawed in new construction and permitted remodels.

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Regards, Tom