Plumbing code question

you're ok. It's called a 'wet stack'.

steve

on 11/1/2007 9:21 AM Steve Barker said the following:

Aren't wet stacks only allowed on the same floor?

re: Aren't wet stacks only allowed on the same floor?

I hope not! My 2nd floor bathroom, 1st floor sink and 4 basement fixtures (full bath and utility sink) all use the same wet stack. There are no dedicated vents for any fixtures in my house.

The 1st and 2nd floor fixtures drain into the cast iron vertical stack and the basement fixtures all connect to the cast iron drain pipe under the slab. Everything works fine as far as I can tell. The only drainage problems I've ever had in 24 years were caused by roots in the town owned section of the drain out by the street.

I have a little trouble following your sketch. Where is the roof vent terminal?

In any case, NO the Lav vent can not be tied into the stack *below* any toilet. This is not what is meant by a "wet vent".

The Lav vent must be extended up thru the 2nd floor to a point above the toilet connection or else have its own vent thru the roof.

Jim

There is/was an exception in the case where the soil stack is 4" size. In this case, the 1st floor and 2nd floor toilets may join the stack without additional venting. Lav trap could empty above the uppermost toilet.

Today, you probably couldn't do things like this, but it was accepted practice and did work.

Jim

I had the same setup and was required to update it to current code when I did some renovation last year. I had to move the downstairs vent so they connected into the stack above the point where the upstairs waste tied into the stack, so that water from above could not flow past the vents. It can be a small vent, I ran 1 1/2" PVC alongside the stack and reconnected in the attic.

Your question of "where is the roof vent terminal" for the lav is exactly why I find the existing condition peculiar: the 1st floor lav vent ties directly into the stack *below* the 2nd floor toilet. If this layout is not the definition of a "wet vent", I think I'll have to extend the vent up as you suggest (please confirm).

Then, assuming the vent is rerouted and the issue resolved, is there any restriction you can think of against tying the lav drain directly into the stack below the 2nd floor toilet per the proposed sketch?

I believe the cast soil stack is 4" so I guess my house is exceptional. :-)

However, this statement confuses me: "Lav trap could empty above the uppermost toilet"

The uppermost toilet is on the second floor, and obviously the toilet drain is on the floor. How could anything empty *above* this?

Both the sink and tub empty into the pipe that the toilet sits on, just a few inches below the shoe.

Ah. That's a side-inlet to the "closet bend". It wouldn't normally be done without some vent provision, but could have been allowed by local exception. It worked and that was the ultimate test.

Over the years, every state/county had their own interpretation of what constituted good practice. Unlike the Electrical Code, we never had just one plumbing code.

Jim

Yes, extend the vent up. Once the Lav is vented properly, the drain can tie in below another fixture (such as the toilet).

Jim

If you are unable to extend vent to roof or above 2nd floor toilet, consider using a mechanical vent installed at the sink. Just remember to keep it accessible for inspection and maintenance.

Although not the best solution, it will work and may be permissible. Good question to ask your local plumbing inspector. Sometimes codes vary from locale to locale.