In line sinks on horizontal drain

[Chris Emerson]

We are adding a restroom and an old warehouse in Seattle. Because part of the drain line has to go over a concrete footing it starts at its lowest point about 10 inches above floor level. There are two sinks and for each we are using a combo 2-in tee on its side, it is not possible to change this configuration.

The two sinks are right next to each other. Originally, as in the photograph here there was a vent immediately after the left sink which placed it to close to the drain for the right sink. And one of the inspections we were told that that was not legal and that given the constraints we would have to use AAV. The problem is this means the plumbing underneath the sink will stick out too far.

Edit: Note that the line from the left comes from a laundry tray which has it's own vent line. Not shown in the photograph is the horizontal vent line about 5 feet high.

Would it be legal to have a vent after the first sink and then another vent after the second sink? Is there some other solution?

Thanks

https://photos.app.goo.gl/BM7FBEdKLrsBgAW49

 

[wwhitney]

What's coming in from the left?

Edit: If you can accommodate raising the sink inlets in the wall 4", you can use a wye/45 to keep each sink fixture drain separate from the main horizontal line until after you have your vent take-off.

Cheers, Wayne

 

[Sponsor]

 

[Chris Emerson]

What's coming in from the left?

Edit: If you can accommodate raising the sink inlets in the wall 4", you can use a wye/45 to keep each sink fixture drain separate from the main horizontal line until after you have your vent take-off.

Cheers, Wayne

Unfortunately the drains are already at close to 20". One of the sinks needs to be ADA. If I do that then the sinks become to high.

 

[Chris Emerson]

Unfortunately the drains are already at close to 20". One of the sinks needs to be ADA. If I do that then the sinks become to high.

There is a "laundry tray" coming from the left. It has a vent.

 

[hj]

A vent 'AFTER" the drain connection is usually worthless, if it is not the ONLY drain connection to the line.

 

[wwhitney]

Other than wet venting (not allowed with the laundry sink upstream), you need to vent each fixture drain before it combines with any other drain. If the laundry sink weren't there, the configuration you have for the two lavatories would be an acceptable wet vent for the righthand lav.

So one possibility is to raise the laundry drain 4", have it pass in front of or behind the vertical vent, and then join the lav drains downstream of both lavs. You could reduce the vertical vent to 1-1/2" to help make things fit in the wall, but you'd still have to fir out the wall. Or else let the vent pipe bulge out of the wall as it jogs across the 2" laundry drain.

Another possibility is to core drill the concrete footing, so you can exit the building at least 4" lower, and route the laundry drain under the lav drains.

Or if there's any way to rearrange the fixtures, so the laundry is to the right of the sinks, then you don't have the crossing problem.

Cheers, Wayne