Tub Drain Line Question

[LegoMyEgoLess]

Been lurking for some time, but now have need of some custom advice

I'm doing a bathroom renovation and will be replacing a corner garden tub with a standard drop in model. The drain from the garden tub needs to be moved about 24 inches. My plan is to cut away the existing P trap, use some 45 degree couplers to route the drain to the new location, then install a new P trap. My question: is this "OK"? Forgive me, but plumbing really isn't my "strong suit". Everything I've seen and read has the drain pipe on a direct line to the main drain/vent but I can't find anything that states this is required. I just want to make sure that routing is not going to cause a problem. I'd like to avoid cutting all the away across my slab to the main drain if I can avoid it.

I tried to upload a rough sketch of the existing/proposed drain pipe but for some reason I couldn't get it working.

[Fairview]

While I'm sure there are plumbers around to help you here, you might want to post up at Terry Love's plumbing forum (Google it).

Aside from that, if you're not creating any traps for the water, and maintaining a 1/4" per foot slope to the main stack, you should be ok. Moving it 24" means the horizontal pipe will be 1/2" higher in the slab than it is now - before it enters the P trap.

So as long as you have the depth to accomodate the P trap in the slab 1/2" higher than it is now, you will be fine. Just maintain the slope through the 45 degree bends and keep the turns to a minimum.

What will be the overall distance from the new drain to the stack, and where is the vent for this drain?

[COsborne]

If it has a drain, a trap is required (unless it has an integral trap, like your toilet does, or say, a grease interceptor), per the Uniform Plumbing Code. In other words, if you're doing this on a permitted job that's going to be inspected, you'd better plan on putting one in.

That, and you probably don't want sewer gases coming up into your home forever. It's not great for your health, not to mention the methane issues.

[LegoMyEgoLess]

Depth won't be an issue... in its current location, the pipe is about 12 inches down.

The new drain will be about 8 feet or so (increasing from about 7 feet) from the main drain line. The vent runs up the same wall, so about 8 feet or so.

[LegoMyEgoLess]

I know I must be missing something... but I'm planning to relocate the p-trap to the new drain location. I have no intention of leaving it off - the smell would be unbearable. Is that what you mean? If not, could you clarify? I really don't want this to be done improperly

I probably wasn't clear, but I only want to introduce a couple of 45 degree bends in the existing drain line to the main to accommodate a new tub drain location (with trap).

[bbcamp]

According to my old copy of the Standard Plumbing Code, a 2" drain with a 2" trap sloped 1/4" per foot must be 6 feet or less from the vent. The measurement is along the pipe, not as the crow flies. 45 els are OK. Sounds like you are going to be a bit over the developed length limit. If this is going to be inspected, now would be a good time to call the inspector and request an interpretation or deviation.

If it isn't going to be inspected, keep on truckin'.

[LegoMyEgoLess]

Hmm... I'm glad you said something, because it's definitely over 6 ft (already is). Oddly enough, it was 7 ft as built by original contrator... how the Hades did that pass original inspection. I'm going to verify local code and abide by it. Everything is already ripped up anyway... may as well do it now. That sucks though, because I'm going to have to call in a pro to put in a new vent

Thanks for the information.

[Fairview]

So the vent off the 2" tub drain line runs up parallel to the main stack, and exits the tub drain line right near the main stack?

Is there any opportunity to put a vent on the tub drain line closer to the P trap and then up and over to the existing vent?

If the vent is too far away, theoretically it won't do its job to keep the water in the trap from being sucked out, and the tub may drain more slowly.

If the tub drain is close to a framed wall, which I presume logically it must be, you might be able to trench over to the framed wall and bring a new vent line up and then over to tie into the current vent. I don't think there's an issue with having two vents off the one drain line.

All that being said, no harm in putting the pipes together the way you want (glued) and putting a big funnel on the P trap. Then run water into it with a hose or buckets to see how well it drains and if the trap remains full of water afterwards, as it should. If so, and if no plans for a measuring-tape carrying inspector, as was said, keep on trucking!

You want to make sure it all works well before pouring concrete of course

[Fairview]

Oh, and is this a bungalow or multi-story house? What's above the bathroom?

[LegoMyEgoLess]

This is a detached, single story house (so nothing but a roof overhead )

It turns out that I was able to re-route the line much closer to the vent than I originally thought, and subsequently required only a single 22.5 degree elbow. Also, I framed a larger shelf on the far side of the tub frame which will bring the tub out that much farther. The end result was a single 22.5 degree elbow with an increase of pipe run of only about 6 inches.

I did follow your suggestion regarding a "wet test", and everything appears to be functioning as expected.

Thanks for all of the advice and comments.