Wet Vent Under Slab

Pkin · Oct 6, 2011

Vent Under Slab

Hello All,

I would like to move a shower drain that is located under a slab in my home:

I am planning to move the shower drain by removing the existing shower trap and extending the 2" line. At the new position the drain will be about 8' from the existing vent, and so I am planning to add a vent near the new drain trap. The cleanest solution for me would be to run the vent under the slab so the side of the shower before going vertical. The following pattern is given in the book "Plumbing a House" by Peter Hemp, Taunton Press, 1998. And I guess this is just wrong???

Pkin · Oct 6, 2011

Regarding adding a cleanout upstream of the shower drain, it seems like its required, but I don't understand why a clog couldn't be removed by simply running a snake through the drain. So maybe its not required?

Sponsor · 2022-01-29T12:20:58-0800

Cacher_Chick · Oct 6, 2011

It's apparent that you have no idea what a wet vent is.

Here a 2" drain with 5' between the trap and vent would meet our code if it is pitched at 1/4" per foot, but YOUR plumbing code will be the determining factor.

If your new drain line is 8 feet, you will need to re-vent it, which means coming up vertically within the minimum distance. You cannot tie the vents together below the flood rim of the highest fixture.

Pkin · Oct 6, 2011

Thanks for your consideration. I have 8' not 5' so I need to add a vent closer to the new trap. Can I run a vent horizontal as shown in the drawing as long as I plumb it as if it were a drain and keep the vent sloped at 1/4" per foot?

And do I need a cleanout somewhere upstream of the shower drain if its 8'?

Thanks

Cacher_Chick · Oct 6, 2011

NO.... You cannot run a vent horizontally anywhere below the slab! The vent must come up vertically within the minimum allowed distance.
A cleanout for a shower will often be in the vent riser.

Depending on the layout of the fixtures and main line, it is sometimes possible to wet vent a tub/shower through the lavatory. The only time a wet vent is permitted in a bath is through the lavatory.

Pkin · Oct 6, 2011

Thanks for the help!

Jimbo · Oct 6, 2011

It would only be a wet vent if another fixture...such as a sink....upstream, drained through that section of pipe.

hj · Oct 7, 2011

Do NOT call it a "wet vent" because the ONLY time it would be "wet" is when the shower backed up, and that would be the WORSE time for it to be wet because every time it happened, debris would enter the vent, and without something to wash it away, it could eventually close the vent. Your rudimentary drawing does NOT give us enough information to tell HOW you could install a vent properly, but I am sure the new shower is NOT 16' wide.

Pkin · Oct 7, 2011

OK ... an actual wet vent would be allowed because debris could be washed out. Now I get it.

And that means that the following pattern is NOT allowed
( from "Plumbing a House", by Peter Hemp, Taunton Press, 1998.)

Thanks.

Kentd · Oct 7, 2011

In the book diagram, what if you were to put a cleanout on the vertical portion of the vent (above floor level)? In that case you could unclog the horizontal portion of the under slab vent via the cleanout.

Terry · Oct 7, 2011

The drawing shows fittings that aren't even allowed below grade.
The 90's are vent only, to be used at least 42" above the floor.
And the Santee on the horizontal should have been a wye fitting. Peter Hemp doesn't have much of a clue.
I would like to see him get that passed anywhere with a plumbing inspector.

If your shower has walls on three sides, then the wye fitting could have been used and gone up vertically in the first wall it passed.

hj · Oct 8, 2011

That drawing was made by someone who actually believes "any one can be a plumber" if they just buy enough pipe and fittings to make it work. And since it is in "your own house" you do NOT need to worry about permits or inspections.

Tom Sawyer · Oct 8, 2011

The fittings are wrong and unless that "vent" is washed by a fixture above it is flat and below the flood lever rim so it's not allowed either

nepats · Nov 5, 2011

Hi, I was wondering would the diagram be allowed under this MA code.
(b) Vertical Rise.

1. Where vent pipes connect to a horizontal soil or waste pipe:
1. The vent shall be taken off above the center line of the soil or waste pipe drain.
2. The vent pipe shall rise vertically, or at an angle of 45E from the vertical, to a point at least six inches above the flood-level rim of the fixture it is venting, before it may offset horizontally.
2. If it is not possible or practical to vent the fixture trap as required in 10.16(7)(b)1.:
1. A vent serving a floor drain, floor sink, or similar floor mounted fixture may be extended horizontally above the centerline of the drain of the fixture to the nearest practical location where it can rise vertically.
2. The vent shall connect to soil or waste pipe above the centerline of the drain not less than 45E from the horizontal before running in a horizontal position.

Tom Sawyer · Nov 6, 2011

In Mass it't gonna depend on who inspects it. Theoretically Mass does allow a flat vent but in practice most inspectors are not gonna let it fly

Wet Vent Under Slab

Users who are viewing this thread

Pkin

New Member

Attachments

Pkin

New Member

Sponsor

Paid Advertisement

Cacher_Chick

Test, Don't Guess!

Pkin

New Member

Cacher_Chick

Test, Don't Guess!

Pkin

New Member

Jimbo

Plumber

hj

Master Plumber

Pkin

New Member

Kentd

New Member

Terry

The Plumbing Wizard

hj

Master Plumber

Tom Sawyer

In the Trades

nepats

New Member

Tom Sawyer

In the Trades

Similar threads