View Full Version : Washing Machine Drain

12-27-2012, 02:30 PM
I'm remodeling a 1955 rancher. I have access to the basement below and the attic above. Currently I'm in the existing half bath and am adding laundry equipment to it. There is an existing 3" cast iron wet vent that has a toilet tied into it (3 x 3 x 3 sanitary T approx 2' run) and the sink tied into it above the toilet tie in (3 x 3 x 2 sanitary T approx 3' run). Can I tie the washing machine into the same wet vent? If so it would be approx 2 1/2'. If allowable, would I use a double sanitary t/sanitary cross or put sanitary Tees above each other?

Thanks for the help - Mike

12-27-2012, 02:38 PM

The washer has to go downstream of the vent for the toilet.
Only bathroom groups can wet vent


A washer will have suds, and dumps at a greater volume. It's a different kind of animal.

12-27-2012, 02:48 PM
OK. Thanks for the quick reply. It would have been too easy with everything that close and (now) exposed. Looks like I'll have to go up to the attic with an aav (sudor vent) and down to the basement to an available wye.

12-27-2012, 02:57 PM
You can tie into the existing vent, and probably should, but it must be at least 42" above the floor of the drains served by that vent line or 6" above the flood plane, whichever is higher. You can tie it to the vent in the attic. Avoid AAV's when a proper atmospheric vent is available. Both you and the inspector will be happier!

12-27-2012, 03:48 PM
Jim -
Good point - just didn't want to make another roof penetration or mess with breaking cast iron. But may reconsider tying in. I wish it wasn't an issue with the washing machine p-trap below the floor - which would be more accessable than in a drywalled wall. Otherwise, I could tie it in below the toilet.

Thanks - Mike

12-27-2012, 04:28 PM
UPC 804.1 All plumbing fixtures or other receptors
receiving the discharge of indirect waste pipes shall be
approved for the use proposed and shall be of such
shape and capacity as to prevent splashing or flooding
and shall be located where they are readily accessible
for inspection and cleaning. No standpipe receptor for
any clothes washer shall extend more than thirty (30)
inches (762 mm), nor less than eighteen (18) inches
(457 mm) above its trap. No trap for any clothes
washer standpipe receptor shall be installed below the
floor, but shall be roughed in not less than six (6)
inches (152 mm) and not more than eighteen (18)
inches (457 mm) above the floor.

The top of the standpipe MUST be above the FLR of the appliance no matter what, and it sounds like your code wants a minimum dimension of 18", and a maximum dimension of 30", for the standpipe dimension.

12-27-2012, 04:41 PM
Terry -
Thanks, got it. As I said I wish it wasn't an issue with putting the p trap under the floor but I know it is, so on to plan B. What I was saying is I may reconsider tying the vent into the existing in the attic rather than an aav.