Double fixture tee or double sanitary tee?

[nc8861]

For DWV on a single vanity to double vanity conversion.

Double sanitary:
http://images.grainger.com/images/products/small/SMALL-1WHU8.JPG

Double fixture:
http://images.grainger.com/images/products/1CNT8.JPG

Can anyone recommend an online site for ABS fittings such as this (also on a 4x3 closet bend)? My local shops don't have them.

[Terry]

If you are doing back to back toilets, it needs to be at least the double fixture fitting.
And even with that, the waste from one toilet will cross over into the other arm, forcing the water up in the bowl, and then leaving it with less water.

I becoming a big, I'm not a fan of any kind of cross for todays toilets.

http://www.terrylove.com/images/double_lav_rough_1.jpg

[nc8861]

Thanks Terry - see OP though - these are two sinks on a double vanity.

Another question - do these fittings have the slight drain angle built into the fitting?

[patrick88]

The fitting you have shown are for vertical use.

[hj]

The double fixture fitting is the only one approved for back to back installations although it is possible a cross could slip by an inattentive inspector. The hubs have enough "slop" in them that they do not need built in pitch. You can install the pipe with the proper pitch, reverse pitch, or 'excessive' pitch just by holding the pipe at the desired angle as it cures.

http://www.terrylove.com/images/abs/abs_fixture_cross.jpg

[sjsmithjr]

The pic below of double lav install (I believe it's from one of Terry's jobs) shows the correct configuration using a double fixture fitting. For the ABS fittings, Google "plumbing supply" and go with the famous one.

[hj]

The only addition to the picture, unless it is dropping directly into a main line would be a cleanout tee beneath the fixture fitting. Although a snake will drop down the stack, removing a trap to clean the line is not a proper cleanout method in this area.

[nc8861]

Thanks all - I do already have an existing cleanout beneath the existing (single tee) fixture. I'm planning to cut above and below the existing single tee, & add my double tee.

When adding a section of dwv pipe back in this vertical way, what's the best way to get couplings squeezed in there? In other words - if I come back with pipe to fit the exact length that I cut out, there won't be room to get couplings in where I need. I was thinking that I glue the bottom joint (between the tee and cleanout), and then on the top joint (above the tee), I use a rubber coupling? What do you all think?

[sjsmithjr]

I believe you could use a banded coupling like this one, which is suitable for above ground use:

http://www.fernco.com/images/proflex.gif

But whatever you do don't use one like this, which is for below ground only:

http://www.fernco.com/images/1056_44.gif

A slip coupling would be another option to conisder.

[nc8861]

Sam - Just for the sake of explanation - why don't you use the type you pictured in the lower picture?

[nc8861]

And just to review - it's only when I'm doing a back-to-back installation (i.e. two different rooms) where I need a double fixture tee, right? Same room, two sinks = double sanitary. Correct?

[Terry]

Where I am at, you would need a double fixture fitting, regardless.

http://www.terrylove.com/images/abs/abs_fixture_cross.jpg

[sjsmithjr]

Sam - Just for the sake of explanation - why don't you use the type you pictured in the lower picture?

My 50 cent explanation: the steel band in upper pic reinforces the coupling making for a connection that won't offset or separate. The coupling in the lower pic relies on the soil backfill to reinforce the coupling.

Also, look closely at the coupling in the first pic - notice the stop for the pipe in the center and the ridges at either end to seal the joined pipes. The coupling in the second pic does not have these features.

[hj]

The same fitting regardless of where the sinks are located.

[nhmaster]

The IPC will let you use the double san tee in the configuration that you want to use it for, HOWEVER if you have to snake the drain you'r gonna have troubles because the snake is going to pass straight through and not go down. We can not use double san tee fittings for back to back blow out type fixtures. I would follow Terry's advice and go with a double fixture Tee.

[hj]

The IPC is a cost driven code, and since a double fixture fitting costs more than a cross, the cross will be allowed even if it does cause operational problems later.

[jimbo]

I don't know it it was allowed by the CA plumbing code at the time my condo buildings were built ( 1985 ) but I assume we have double san tees on the back to back closets, because on two occasions in the last several years, plumbers called in by homeowners have pulled the guy's toilet and run a cable down, which promptly came up inside the adjacent apartment and beat the toilet to death!

[hj]

It can happen with a back to back fitting also if the cable is very stiff. It will hit the slope of the other side and then make the gradual turn to go upwards.

[nhmaster]

The IPC is a cost driven code, and since a double fixture fitting costs more than a cross, the cross will be allowed even if it does cause operational problems later.

Never heard it called that, but I like it. I prefer to think of it as a manufacturers code. Or conversly the Idiotic Plumbing Code.

Hell, now I'm all stirred up again and feel like having a screeming contest with the state board members again. They're gonna get a restraining order on me pretty soon.:D

[Basement_Lurker]

If you are doing back to back toilets, it needs to be at least the double fixture fitting.
And even with that, the waste from one toilet will cross over into the other arm, forcing the water up in the bowl, and then leaving it with less water.

I becoming a big, I'm not a fan of any kind of cross for todays toilets.



So what are you in favour for then Terry for horizontal to vertical applications like a back to back toilet installations? A double wye? Or do you only prefer to use a double wye if a double fixture fitting is not available?

[nhmaster]

A lot of time a double wye and 1/8 bend take up too much space, especially in residential work. A double fixture fitting is a whole lot more compace. They are fairly common, though the box stores probably won't have them. If the fixtures are not blow out tye, you can still use a san tee by the IPC and UPC but again, they make cleaning a little more difficult. To be honest I usually try to use std fittings and offset the drains so that a regular wye ir san tee woll work.

[hj]

If a double Y with 1/8 bends were acceptable there would be little need to manufacture a double fixture fitting. But since it would create 3/4 "S" traps and possibly not fit in the space available it is even less acceptable than a sanitary cross.

[Basement_Lurker]

But is a double fixture fitting really the best fitting for a back to back toilet installation? Would using a double wye really put either of the toilets at risk of self-siphoning?

I currently use a double fixture fitting in this application, but I somehow think using a double wye would be better.

[jdgoodman]

You would not be able to use a double wye on a back to back setup because the weir of your trap would be higher than you vent take off. UPC accepts san crosses if the barrel is 2 pipe sizes larger than your branches.

[hj]

Our inspectors will not approve an double Y for that type of installation, even though it does not affect the operation of toilets like it would sinks. We always use a back to back fitting.

[Jampel]

I am trying to figure out if my situation applys here. I have a shower drain and a kitchen sink i am trying to drain and vent. because of the angle of the horazontal waste line in the basement beneath the shower, i would like to 90 bend up, with a double Tee on top of that, right branch going strait to the 2" shower p-trap, left branch going to pick up the kitchen sink (the sink is re-vented above the high water level of the fixture, the shower is not), the top of the double Tee, being the vent, goes up through the floor, between the shower and the sink (in the back of a closet) and then has a clean out wye accessable.

I want to use a double Tee because the space is so tight (the sink and the shower drains are about 4 feet apart). I already called my inspector and asked about useing a double san-tee, he said no go, unless the shower was somehow re-vented also. I am now wondering if a double fixture fitting would be alright in this situation. If it is not (or even if it is) then could some one please help me understand in what situations these three fittings are to be used? BTW I am in minneapolis so the inspector is very thorough.

PS. My name is Jampel, and thank you to Terry and all the people on this site, i have read and benifited from many threads here but this is my first post.

[Terry]

Jampel,
The sink and the shower trap are not close enough to work on a fixture cross together.
The shower trap is below the floor and the sink needs to be above the floor.
That means the shower would need it's own vent, that can be "revented" at 42" above the floor with the kitchen vent.
Instead of a fixture cross, you would have a santee pointing out for the shower, vent and then p-trap.
Above that on the next floor, santee pointing toward sink, with the vent out of the top that then revents at 42" to the shower vent.

http://terrylove.com/images/dwv_b2.jpg