View Full Version : Tub Drain--double trap?
09-07-2005, 07:21 PM
This is my first post here. Have been checking up on my construction guy's work on our bathroom remodel over the past few weeks. Today he finished up the plumbing on the tub and I have a concern/question. The bathroom is in the basement. We put the tub (Memoirs 5.5 ') over the pre-existing drain that had been used for a shower. He built a subfloor over the basement floor (6"). He put in a trap (1 1/2 diameter) from the tub drain and then it goes over about 9" to the pre-existing drain in the floor (2" diameter). I thought the pre-existing drain in the floor was already trapped and another trap would not be needed. I asked him and he says, "yeah it's probably already trapped". And, it seems the tub drains a little slowly. Is this a double trap, or an s trap with a pre-existing trap in the floor and is this all way wrong, a little wrong or OK and I am just a being a completely obsessive homeowner hoping my 18 thousand dollar BR is perfect? Please be kind. The guy has done a beautiful job with everything. I do think his weak point may be plumbing though. Of course, I really know nothing--that's why I'm here. Thanks, Dave
09-07-2005, 07:46 PM
If you can, take pictures of the connection of the tub where the trap is. This might give some clarity to the situation. If there was a box out underneath then possibly there wasn't a trap there, just a stubout like most.
09-07-2005, 08:05 PM
This is why plumbers should plumb and handymen shouldn't.
There is no good reason to have two traps on a tub drain.
09-07-2005, 08:14 PM
he probably should have jackhammered out the floor and moved the drain to new location. then wouldn't have needed the platform. he would have needed access to connect tub drain to trap. possibly wall at drain end.
nice to hear he did a beautiful job with everything. must have some skills.
09-07-2005, 11:29 PM
He should have known for sure, not "yeah its probably already trapped". If in fact your tub is double trapped (and I suspect it is) this needs to be fixed as it will cause you nothing but trouble. In the future, I'd suggest leaving the plumbing to a plumber.
09-08-2005, 02:58 AM
Couple things--there is, I think, what you referred to as a "box out" around the main drain pipe. The photos don't show the box out well. I never saw how the old shower was connected to the drain. Maybe the shower had a trap and that's why he put in a trap with the tub. The BR was pretty much completely gutted before I got home that day. BTW--the tub drains pretty well. My previous reference of "draining a little slow" is, I'm sure, quite subjective.
Here's a link to a couple of photos:
Well, you not only possibly have a double trap, because the plumber may have been incompetent, but you definitely have an "S" trap, which removes any doubt about his competency. If you have anything going for you, it is that an "S" trap will drain better than a conventional "P" trap, and that may be enough to overcome the second trap. But when the tub drain becomes obstructed, which it will, that double trap may make it almost impossible to snake. A single trap can be bad enough.
09-08-2005, 08:41 AM
Yep. Pictures tell the story. The very reason I asked. Curious to know if it was properly vented as well. It would be all upon your shoulders what to do at this point as you know every runs like a scalded dog with no problems. It is what you have to deal with months/years down the road. There is also a chance that when the tub is drained that a S-trap config like you have can siphon out. Probably not likely but anything is possible when plumbing is installed incorrectly.
09-08-2005, 09:33 AM
I would determine if there is a trap in the ground, and a vent for it. If so, I would remove the 2nd trap and run sweep 90's to it.
Like hj says, snaking is going to be a tough job here.
Best would have been to move the trap and run the pipe straight up.
What I also don't see, is any support for the bottom of the fiberglass tub.
If this is a deck mount tub, there will be a lot of pressure when you add water and somebody jumps in.
Most installers are using something like mortar mix, plaster or at least shimming the bottom.
09-09-2005, 05:18 AM
Thanks for all of your input. I discussed this a little more with the installer. There's wasn't a trap in place when he removed the old shower (put in either when house was built ('79) or soon thereafter. It drained into the stub directly. He didn't see water in the stub. Interestingly though, we never had any odors from this shower and it wasn't used often at all either. This drain is only about 8 feet from what appears to be a large "stack" as I think you guys call it. Again, this is in the basement. I am planning on having a plumber look at this when I have him out to install a booster pump to increase water pressure in the house. We will always have easy access to the trap and the area seen in my pics (previous post).
One more question, if there is a trap needed here, can this configuration (s-trap) be converted to a proper p-trap the way the tub is presently situated with the location of the drain?
BTW--in response to Terry's concern about the base and tub setting: The tub (Kohler Memoirs 5.5') has several little fiberglass molded "feet" that are shimmed properly on a rock solid platform as per the Kohler instructions. This is not visible in the pics I posted. Kohler recommends either construction adhesive used directly between the tub and base/platform with or without shims as needed. My builder/installer and I had discussed a mortor base because that is what he usually does but we decided to follow Kohler's recommendation. There was only a fraction of a centimeter between the tub and platform. The tub is not supported by the lip. Remember, I inspected the work everyday and then consulted as a lurker to this list quite often checking things out!
Thanks again, Dave
I find it hard to believe that the old shower did not have a trap, although I suppose if it was installed by a DIY'er it could have happened. But I might question the analysis on any plumber who thought installing an "S" trap was the proper way to connect any fixture. In any case the trap as situated is improper, and will give you problems. It is possible to install a proper trap, but will involve some concrete breaking.