We are having problems with odor in our shower. I plan to replace the existing shower with a new tile shower but need to figure out whether the shower has a p-trap as we have been told houses on slab do not have a trap for the shower. How do we confirm if we have a trap or not? Given the odor, I'm ready to start jack-hammering...
Charlotte, nc

We always install a "P" trap when we rough in for a shower. How you can tell if you're trapped is to remove the strainer and shine a light down the raiser. You should see standing water that's about at least 2" deep. Regards, Tom

Quote:

---

Originally Posted by rdbond

We are having problems with odor in our shower. I plan to replace the existing shower with a new tile shower but need to figure out whether or not the shower has a p-trap as we have been told houses on slab do not have a trap for the shower. How do we confirm if we have a trap or not? Given the odor, I'm ready to start jack-hammering...
Charlotte, nc

---

If there is a p-trap directly under the drain you should see water, usually a p-trap is not any farther than the shower stall perimeter near a vent stack. In a slab, the p-trap would be in the drain center as mentioned. If this is cast iron probably not to UPC now. Try not to destroy the drain line to the center where the pan drain is because you can use a rubber sleeve over the pipe to connect new plastic DWV pipe and p-trap assembly without needing to do too much jack hammering that depends on where the vent is also. Good luck. Nm

Try not using the shower a few days and feed something flexible down it about 10 feet. If you hit a spot where it will not go within 5 feet of the shower it may have an offset p trap. When you pull it up, is it wet?

"it may have an offset p trap."
Doug, Are you referring to a running trap,(see image)? Because that's what you'd have if you moved a "P" away from under the drain. In all the hundreds of "under slab" shower installations my company has installed we have never iroughed in a running trap for a shower. Nor could I ever conceive of a situation where we would be forced to rough in a running trap in place of a regular "P" trap. Now I admit my code book is a little old and not up to date so if I'm missing something let me know. Regards, Tom

Quote:

---

Originally Posted by speedball1

"it may have an offset p trap."
Doug, Are you referring to a running trap,(see image)? Because that's what you'd have if you moved a "P" away from under the drain. In all the hundreds of "under slab" shower installations my company has installed we have never iroughed in a a running trap for a shower. Nor could i ever concieve of a situation where we would be forced to rough in a running trap in place of a regular "P" trap. Now I admit my code book is a little old and not up to date so if I'm missing something let me know. Regards, Tom

---

Hi speedball,

Thanks for the running trap defiinition. I am learning every time you post something. I have seen a running trap in SF years ago done in metal. I guess it is still allowed nowadays? Nm:)

As a rule running traps are installed outside the house in a septic system if there's a odor problem. Regards, Tom

I have seen showers without a trap and the odour is noticeable.
Always done by someone that doesn't know anything about plumbing.
If you are on a City sewer system you can have someone hit the manhole cover on the street with a sledge hammer. The trap not only stops odours and gases it muffles the noise. If you don't have a trap you will hear it clear as a bell.

Quote:

---

Originally Posted by Ken 297

I have seen showers without a trap and the odour is noticable.
Always done by someone that doesn't know anything about plumbing.
If you are on a City sewer system you can have someone hit the manhole cover on the street with a sledge hammer. The trap not only stops odours and gases it muffles the noise. If you dont have a trap you will hear it clear as a bell.

---

Ken, That's clever. Will it work on a septic tank?. :D nm

Its hard to bang on a septic tank hard enough to hear the noise. If you had a steel lid I don't see why not.

Bottom line!
If you don't see water at the base of the raiser you can figure that you aren't trapped. Regards, Tom

A running trap is typically on a main line. We are speaking about a branch line and offsetting the riser is legal and OK.

"offsetting the riser is legal and ok." That may well be but it's simply not good plumbing practice. When's the last time you installed a running trap for a shower rough in under the pour, and why? Regards, Tom

Tom, the last time I did was when I came behind a rough by another plumber and he had missed by about 6 inches on a tub. The trap was deep and I offset with two 1/8 bends. Previously I have used 1/4 bends on a tub rough offsetting about the same but the trap was not as deep. I am not fond of offsetting a riser but will not hesitate to do it.
Also, it is not a running trap. A running trap is in the main designed to 'trap' the system like a safe waste system which is required in Georgia and illegal every where else. In Georgia it is called a master trap and is used on systems that require an underground grease trap.

Quote:

---

Originally Posted by doug238

tom, the last time i did was when i came behind a rough by another plumber and he had missed by about 6 inches on a tub. the trap was deep and i offset with two 1/8 bends. previously i have used 1/4 bends on a tub rough offsetting about the same but the trap was not as deep. i am not fond of offsetting a riser but will not hesitate to do it.
also, it is not a running trap. a running trap is in the main designed to 'trap' the system like a safe waste system which is required in georgia and illegal every where else. in georgia it is called a master trap and is used on systems that require an underground grease trap.

---

Doug, That's "piece-O-crap-plumbing" and you know it. A normal shower rough in has the trap raiser directly under the drain. You're giving me half-a$$d cobbled up patch work to save yourself the trouble of redoing it correctly.

"it is not a running trap. a running trap is in the main designed to 'trap' the system like a safe waste system which is required in georgia and illegal every where else. in georgia it is called a master trap and is used on systems that require an underground grease trap."

A rose by any other name, etc. but a running trap is a running trap is a running trap, period.. I guess you missed the 2" PVC running trap I put up earlier. Cheers, Tom

Quote:

---

A rose by any other name, etc. but a running trap is a running trap is a running trap, period.. I guess you missed the 2" PVC running trap I put up earlier.

---

Technically, it isn't a 'running trap' until the offset at the inlet meets or exceeds 90 degrees horizontally.

When offsetting a riser with two 22's, 45's or 60's, the change in direction is still considered vertical.

Just my two pence.

I wasn't talking about a offset raiser and neither were you w3hen this thread started.
You said,"Send something flexible down it about 10 feet. if you hit a spot where it will not go within 5 feet of the shower it may have an offset p trap.

When you have a underground "P" trap that's so far outta line that you have to ell over to ell up for a raiser youi have built a running trap under the slab.
You started out with a "P" trap and ended up with a raiser. Since I confuse easily please bset me straight.
Growler, you're correct but again, I'm talking traps not raisers. Cheers, Tom

Hmmm, piece of crap plumbing? Offset traps and raisers, oh my.
Tom, a running trap is a trap that is on a main line. The sole purpose of a running trap is to have a second trap in the system. This is why the code says to not double trap a fixture, it causes an airlock. Now I agree that an offset riser on a trap is not an ideal situation, but it is legal. I have offset risers on a tub, a shower, a washing machine, a handicap lavatory, and a sink. Offsetting the riser does not interfere with the flow of a fixture drain. While offsetting is not our first choice it is a choice, and in some cases that choice is called on.
Plumbing Terminology R
Running Trap An in-line trap mounted in a horizontal drainpipe, where the inlet and outlet are parallel.
It is my belief that a trap on a drain line that was used specifically to 'trap' the system is what the code is referring to when it speaks of a running trap or double trapping. It is my belief that offsetting a riser on a line to a fixture drain is not the same as the intent of a running trap.

Doug, " it is my belief that offsetting a riser on a line to a fixture drain is not the same as the intent of a running trap."

And you would be entirely correct. But we aren't referrinf to raisers are we?
You said,"Send something flexible down it about 10 feet. if you hit a spot where it will not go within 5 feet of the shower it may have an offset p trap.

We are talking about a trap that's under the slab 5 (count em!) five foot away from the shower drain. Now in order to connect to the shower drain a street ell has to go on the trap to take it over to another ell that raises to the drain.
Doug, Lay it out on paper, (or simply look at the image i put up) by installing a street ell in the trap where the raiser should go you have just built your self a running trap. Now I don't care what they call it up in Georgia or rather you believe that a running trap can only be installed on a sewer main.
The plain truth is that when you install a street ell on a "P" trap you have built a running trap. And if you cobble a underpour trap that's five foot away from a shower drain to pick up the shower without first moving it under the drain that's simply not good plumbing practice, and by any other name it's still a running trap. Regards. Tom

Tom, I agreed long ago that it was not good plumbing. But I also told you that in some cases it is done because of varying reasons.