Help with basement bathroom plumbing

[PaulG333]

Hi all,

I have an existing bathroom in the basement (54" x 60") that was built on a 2x4 platform above the slab. After removing the platform and breaking up the slab, I have a few questions. The reason for redoing the plumbing is because when the plumber branched off the old cast iron drain, he put a slope on the new ABS of at least 3" per 4 feet so that drains and toilet flange would end up at the right height for a bathroom built on a platform, which didn't work out so well for me when I wanted to put a toilet flange at slab level.

Anyhow...the old toilet and tub always drained well and didn't siphon dry even though there was no vent, which I will try to add into the system now that I'm redoing it. The sink plumbing was capped off for some reason at platform level, I'm guessing because it was getting siphoned when the toilet flushed. The sink drain was then run to a different drain that doesn't connect to the bathroom drains at all.

I've attached pictures of the planned plumbing. I realize the vent size is probably small at 1.5", but I won't be running a 2" drain up through the roof at this point in time. Here are the questions:

1) Is the vent size really too small at 1.5" for the wet vent (sink)?
2) How should I handle the 2" vertical rise at the tub? Would 22 degree fittings be best to maintain flow? I'm not redoing the drain under the tub (also on a platform) at this time, so I want to leave the 2" rise there as close to the tub so I can lower the under-tub drain at a later time.
3) To connect the 4" cast iron to the 4" ABS under the slab, is the Mission CP-44 (Fernco 3000-44) the right shielded coupling to use?
4) Can the 4x4x3 ABS be a sanitary tee or long-radius sanitary tee or does it have to be a wye?
5) Does the 90 degree vertical to horizontal have to be a long sweep?
6) Can the dry vent for the tub be 1.5" right from the wye, or should I keep it 2" for as long as I can before it joins the 1.5" vent at 42" above slab level?
7) I plan to put the dry vent as much as I can above horizontal to minimize any waste buildup in the dry vent opening, is this a good idea?
8) Where should I add cleanout(s)?
Thanks in advance,

Paul

 

[Cacher_Chick]

Any drain line below the slab must be 2" or greater.
The tub's trap arm cannot jog up or down between the trap and vent, as this breaks the vent. The entire vent for the tub must be vertical until it is above the 42" mark.
The wet section of the wet vent must be 2", but can be 1-1/2" above the wet section.
The horizontal connection to the building drain can be made with a wye and 1/8th bend or a combo. A sinitary tee is only intended for use on a vertical drain.

 

[Sponsor]

 

[PaulG333]

The tub's trap arm cannot jog up or down between the trap and vent, as this breaks the vent. The entire vent for the tub must be vertical until it is above the 42" mark.

I can put the vent on the tub drain and then do the 2" jog down so that solves the first issue, but I can't keep the entire vent vertical until it's above the 42" mark because the connection is in the middle of the bathroom. How about if I use the sink to wet vent the tub drain instead of the toilet, and have no vent at all on the toilet drain? I can put a 4" drain for the entire length of the toilet drain (appox 4' run) if that helps the situation.

 

[Cacher_Chick]

The fixtures need to be properly vented. The shower drain can be routed to a vent going up. Most showers have walls.

 

[PaulG333]

The fixtures need to be properly vented. The shower drain can be routed to a vent going up. Most showers have walls.

In the first picture, the existing tub (which I won't be demolishing) has the drain going to it about 2' from the closest wall, so I can't route a vent to it without a 2' horizontal portion. That's why I asked if I can do a wet vent from the sink drain (2") to vent the tub? For the toilet, I can probably add a dry vent coming off the top of the 3" drain and still have a continuous slab with minimal thickness where the vent will be. Does the toilet dry vent have to be coming off right at the top of the toilet drain, or can it come off at a 45 degree angle from vertical?

 

[Cacher_Chick]

I was not suggesting that you demolish the tub, only reconfigure the drain to a proper vent at the head of the tub. Then again, I would never leave the tub up on a platform, as it screams "bloody hack job".

You can wet vent the tub and the water closet through the lavatory vent if you can stay within the allowed distances between the traps and their vents.

 

[PaulG333]

Thanks for replying

I can't reconfigure the tub drain because the p-trap and everything after it is encased in concrete under the tub until it comes out from under the tub where you see it in the picture. I think I will keep the drains as I have it in the first picture with one change. I'll keep the dry vent servicing the tub drain, but it'll come off the top of the drain, and it'll be on the tub side of the 2" drop. This will put the dry vent above the slab, but I was thinking of putting a step there anyways because the step-over height into the tub is too much. The step will hide the vent, and if the tub is renovated in the future, it will be easier to reconfigure the drain and vent.

Does this sound acceptable?

 

[Cacher_Chick]

The common rules of good plumbing apply in most of North America. Here, vents must remain vertical until they are at least 6" above the flood rim of the highest fixture served. 42" is a standard published height which ensures future construction will not result in a broken vent.

As I understand your description, it would never be allowed here.

 

[krik]

As mentioned in cacher_chick's comment #6 --- I'd vent the shower and the toilet with a wet vent from the sink. Working with the second diagram, come straight left from tub and straight back from wall to meet at 2x2x2 wye + 45 , then go straight left into 3x3x2 wye + 45. Everything 2" from the sink's santee down, and I'd put a 2" cleanout in the wall below the sink too. I believe, but am not certain, that this meets wet venting code requirements (and cleanout requirements as long as you can use the toilet as an end of line cleanout).

 

[PaulG333]

Thanks for staying with me here, I can be a bit thick-headed sometimes, lol.

OK, I think I fully grasp now what you're saying about the dry vent remaining vertical until 42". Going back to post #6 where you said I can wet vent the tub and wc through the lav vent, what are the allowed distances between the traps and their vents?

The tub trap arm is about 3' and includes a long sweep 90, and the toilet will be about 3' before the tub/lav combo will join it.


Edit: Thanks for the reply krik, I hadn't considered going straight across with the tub drain, so that would put the vent joining the toilet drain within 1' of the toilet closet bend.

 

[PaulG333]

Hey folks,

It's been a few months, but I finally decided to tackle this job this week (I decided to wait for the tenant to move out). I think I followed all of the tips you guys provided, except I forgot to bring the drain for the tub straight across to the toilet drain so it vents the toilet closer to the closet bend (I should have re-read this thread before starting). Please take a look at the pics and point out any flaws before I pour the concrete!

Thanks,

Paul

Edit: Pics 1-3 are an overview of the whole system, 4-8 are a closer view, 9 is the 4x3 closet bend, 10-12 are the couplings.

 

[PaulG333]

More pics...

 

[PaulG333]

I had to use a special sleeve (reducer?) on the cast iron to bring the diameter up to normal cast iron (4.38") because my cast iron was closer to 4.20". I special ordered a sleeve that is a 4.17" ID and 4.38" OD, then put the shielded no-hub coupling on top of that. I used grey gasket maker to help fill any depressions in the cast iron, though I did sand/grind away any rust from the cast iron, then painted the rest of the exposed pipe with oil based paint.

I believe I read that the bathroom should be vented by a 2" vent all the way up, but all I had was a 1.5" vent in the basement, so I went with that. There was no vent at all on the fixtures before, so I hope this is adequate.

The 2" coupling I put on the tub drain line because I didn't have enough wiggle room to slide a full piece of pipe in.

One question: I put the 4x3 closet bend for the toilet, but I found that most of the 4" toilet flanges at the big box stores are not a snug fit inside 4" pipe. Is this normal? I only found one that was a snug fit, and it didn't come with a SS ring.