washing machine drain plumbing

[cJ]

I'd like to move my washing machine to a different location in my basement. The proposed location has 1 1/2" PVC drain that exits through the basement wall 42" above the floor running to the septic tank in the back yard (it is a walk out basement). This current drain plumbing has a drop from the kitchen sink above, running to a sanitary tee. One side of the tee is stubbed and capped (available for washing machine), the other end of the tee runs horizontilly to the wall. A sump pump outlet pipe comes up to tie into the horizontil run via sanitary tee just before the pipe exits through the wall.

I'm hoping I can tap into this plumbing to drain a washer. Can anyone think of any issues with this? I'm thinking I would have to add a check valve since the sink upstairs drains into this plumbing (assuming a blocked downstream pipe would cause backup out through the washer drain. Would a typical 1 1/2" check valve cause any flow rate issues (keeping up with washer drain output). There is also a nearby sump pit. Worst case, could I drain into the sump pit and let the sump pit handle it?

Curious what the group thinks,

Thanks

[Speedy Jim]

It doesn't meet Code now so I guess it won't matter what you do with it.

Check valve sounds like a good idea. I would use a mesh screen on the washer drain hose to keep lint out.

Jim

[Slim Bastard]

[kevin]

Why bother with a check valve? If you have a blocked downstream pipe, you are going to get a backup out through something no matter what you do. Would you prefer having waste water spill out your kitchen sink rather than out a washing machine drain in the basement. In your current setup, if you have a blockage near the septic tank (yikes, only a 1 1/2 drain running outside! Does it freeze where you are?), your existing washing machine drain would overflow too, right?

Even in a house plumbed perfectly to code, there is no way to avoid having blockage cause overflow at some fixture -- usually the lowest fixture above the blockage. I suppose you could add a check valve on every fixture, ... which would accomplish exactly nothing useful.

[Andy]

Andy comments: The washer drain is usually an open pipe with the washer discharge hose sitting in it, so the actual pressure is the height of the pipe or

about 3 feet or about 1.5 psi. That is often NOT enough to open a spring loaded check valve. A swing valve, or a backflow valve, maybe. But I don't think its a good idea. If your downstream is blocked, things are going to screw up anyway, and the check valve simply would mean that the stuff will come out somewhere else. I wouldn't mess with putting one in at all. LInt is mostly in the dryer, and the lint in a washing machine should have no trouble negotiating the small washer discharge hose into the larger drop pipe into the still larger buried drain.

Andy

[Curmudgeon]

I just went thru this, and I STRONGLY suspect that that 1 1/2" pipe does NOT go to the septic tank, but is a separate "gray water" discharge system. It has a small distribution box outside and a coupla lines just like a septic tank to disperse detergent loaded water into the ground. In many localities this is the code for septic systems. But the two systems are separate, and the leech field lines run in opposite directions from one another.

3" is minimum pipe size for solid waste disposal to septic tank.