Redoing shower drain and need feedback from plumbers if it will drain properly

MCU · Dec 27, 2011

Hi,

I am redoing the master shower and had to relocate the 2" drain which leads into a 3" stack. All ABS. I tried to make the least number of turns. Please critique and let me know if you see any problems the way I did it. It will be a rainshower with jets so I need to make sure it drains well.

Thanks

hj · Dec 27, 2011

THAT part is okay, but we would have to know more about the REST of the piping because that drain as installed may NOT have a vent on it.

Sponsor · 2022-01-29T12:20:58-0800

Terry · Dec 27, 2011

It doesn't look to have a vent, and it has fittings that make it an S-Trap.

The trap arm from a p-trap can grade down at a 2% slope, (1/4" per foot)

Dlarrivee · Dec 27, 2011

hj said:
THAT part is okay, but we would have to know more about the REST of the piping because that drain as installed may NOT have a vent on it.

You looking at the same picture I am?

MCU · Dec 27, 2011

The vent is actually a 3" vent on the 3" stack . The toilet, a bidet and tub is on the same line . It was this way before and seemed to work great, I just relocated the shower to the next joist cavity and being how it was tight I had to make the p-trap that way and was wondering if It would be ok.

Terry I am a little confused on your comment. What is an S-trap and is it bad?

Dlarrivee · Dec 27, 2011

He is talking about the bend in the trap arm.

Basically the trap can be siphoned dry.

Bluebinky · Dec 27, 2011

Assuming that the venting were OK (doesn't look right to me, but I don't pretend to understand advanced concepts like wet venting), the horizontal run between the 3" and the trap needs to have 1/4 inch per foot slope. The way the ~45 degree ells appear to be turned now (with the large vertical drop) will create path for the trap to be siphoned dry (s-trap).

From the pictures, it looks like you are trying to elevate the trap to keep it above the finished ceiling below. To do that, you need a vent to break the siphon path...

MCU · Dec 27, 2011

not quite sure i follow here...anyway I could ask you guys to draw a quick diagram of how you recommend I do it? I have two 45s...first is to bring the line parallel with the joist and 2nd is to elevate it a bit for a slope but mostly to lift the ptrap above the ceiling below as bluebinky pointed out

Dlarrivee · Dec 27, 2011

I'm also not fond of how the bottom of the joist has been hacked into kindling...

MCU · Dec 27, 2011

i didn't hack the bottom of the joist. i used an angle driver with hole saw. which one are you refering to?

hj · Dec 28, 2011

I was SURE the toilet was on the same line, but WHERE it is determines whether the shower should have its own vent or not. Your pictures were NOT clear as to the fittings you used, because of the water line in front of them, but after seeing your explanation, that SECOND 45 is what turns it into an "S" trap. You CANNOT "elevate" a trap between the trap and its vent. Your shower may have two things going against it. First, the "S" trap configuration allowing "natural" siphonage, and second, if the toilet flows PAST the shower connection, it could also be subjected to siphonage due to the Bernoulli Principle.

MCU · Dec 28, 2011

yes the toilet is after the shower drain...at the end of the line. This is the way it was when it was built 20 years ago. So how would I do this properly on the shower p-trap while keeping it above the ceiling? From what I understand the lowest point of the p-trap must be lower than the lowest point of the 3" line it runs into? Any issue with the bottom of the p-trap touching the drywall? Will it make annoying sound on top of the kitchen table which is right under?

Cacher_Chick · Dec 28, 2011

It would appear that the wye needs to be moved, but it's pretty tough to make suggestions based on the little bit we can see in that picture.

What is connected to the 3" pipe UPSTREAM of the shower?

hj · Dec 28, 2011

quote; From what I understand the lowest point of the p-trap must be lower than the lowest point of the 3" line it runs into?

The "lowest point of the trap" does have an effect, but ONLY if you are trying to justify NOT venting or installing it properly. The real concern is that the BOTTOM of the trap OUTLET CANNOT be above the top of the pipe it is connecting to, AND the vent has to be between those two points level with the outlet of the trap.

MCU · Dec 28, 2011

well the bottom of the 3" is about 1/4" above the forence on the below ceiling and the bottom of the ptrap is just about the same also. The first pic makes it look much higher but in the 2nd you will see what I am talking about. Here is a look at how the line is to give you a better idea. At the end of the 3", whihc is about 30" away from the shower drain there is a Y which drains to basement and other vents to attic

MCU · Dec 29, 2011

anyone please suggest how i can do it properly or a little diagram please?

Terry · Dec 29, 2011

How about your layout, so we can see which fixtures you have, their locations, and where the pipe runs through all that?

MCU · Dec 29, 2011

Here is the pic showing the complete line and also the shower p-trap and vent. I removed the 2nd 45 on the shower drain and it barely clreas the ceiling but it will once I screw the drywall in place with no bump.

Terry · Dec 29, 2011

It looks like a toilet to the left, and then the lav, and then a shower.

Neither the lav or the shower are vented correctly.
The lav is S-trapped without a vent, and the shower is not vented either.

For the lav, you would get rid of the p-trap below the floor, bring the pipe up into the back wall, and at 18" to 20" bring a trap arm out. The vent would continue up through the ceiling.

The shower needs a vent between the 3" waste line and the p-trap.
That vent needs to go up through the ceiling too.
The ceiling in the kitchen will need to be boxed down around the bend of the trap.
The first rule of plumbing, is that water flows downhill. And pay day is Friday. Don't break the first rule.

MCU · Dec 29, 2011

the middle one is a bidet not a lav. If you look at the first pic of post # 18, at the very end you see the 3" draining with a Y (wye) and the vent going up along the wall through the attic. Is that vent not venting the shower and bidet also?

Redoing shower drain and need feedback from plumbers if it will drain properly

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