Under my Sink; questions about my drain connection

[triodesteve]

I want to connect the drain line of my new (to me) Wega into my house plumbing. A look under the sink reveals that the dishwasher drain is hooked up to what I believe is called a tail pipe. I also have a disposal that has nothing hooked up to it (maybe the disposal came after the dishwasher).

Does it matter to which of these spots I hook up my waste line?

My guess is that since the espresso drain runs by gravity, it would be best to choose the lowest point to hook in. I assume that the dishwasher has a pump, so it doesn't bother it to run up hill.

Thanks for your input,
Steve
Walla Walla

[HB]

Note: I'm not a plumber. That said, disposals typically have a tap for the dishwater since it may eject solids that the disposal can take care of next time it's run. Other (pricey) dishwashers have filters and mini food grinders to serve this purpose. I just checked and found (to no surprise) that our plumber didn't bother using the disposal's tap; we've never had a clog.

Personally I would go for the connection with the greatest slope for your espresso machine driptray.

[jesawdy]

I just checked and found (to no surprise) that our plumber didn't bother using the disposal's tap; we've never had a clog.

So where did he connect, downstream of the disposal? Ahead of the p-trap?

[HB]

To a tee on the downpipe of the adjacent sink, which would be an easier installation in this case. If there were a plumbing code requirement that the dishwater empty into the disposal, our city's inspectors would have flagged it; they're persnickety.

[erics]

Does it matter to which of these spots I hook up my waste line?

Hi Steve from Walla Walla and welcome to HB. No, it does not matter.

Some DW pump discharge lines are led to what is called an air-gap (yours obviously isn't) mounted on the sink. In lieu of this, typical plumbing codes allow connection to the disposal provided the DW line is first led uphill to just below the countertop and then connected to the disposal. This prevents any waste from the sink from flowing back into the DW. The disposal connection point has a plastic plug that seals the opening and is designed to be easily knocked out and removed.

So, if your DW has a macerator style pump (mini-grinder as Dan says ) then it would be fine to leave it as is. If not, then connecting it to the disposal MIGHT be a good idea. This would open up the tailpiece connection for the Wega tray drain.

But as I said, it doesn't matter. Just be sure to remove the plastic plug on the disposal should you use it for any purpose.

Eric S.

[LeoZ]

To a tee on the downpipe of the adjacent sink, which would be an easier installation in this case. If there were a plumbing code requirement that the dishwater empty into the disposal, our city's inspectors would have flagged it; they're persnickety.

that sounds odd. if theres a clog, it can backflow into your 2nd sink then, right? i assume theres no trap on the 2nd sink, just a downpipe connecting into the drain line off the 1st?

[LeoZ]

Some DW pump discharge lines are led to what is called an air-gap (yours obviously isn't) mounted on the sink. In lieu of this, typical plumbing codes allow connection to the disposal provided the DW line is first led uphill to just below the countertop and then connected to the disposal. This prevents any waste from the sink from flowing back into the DW. The disposal connection point has a plastic plug that seals the opening and is designed to be easily knocked out and removed.

Eric S.

but most DW lines are plastic flex tube, right? so, by an uphill slope, you mean put a loop in it to prevent waste gases and waste from entering the dishwasher (which should have a small flap or one way valve anyway, i thought), then im with you. otherwise, want to explain further?

[erics]

Yes, most DW drain lines are corrugated, and thus flexible, plastic tube. And by uphill slope, I mean an inverted "U" where the peak of the "U" is affixed to the underside of the countertop or other convenient location about 8-10 inches above the disposal's DW drain connection.

To the best of my knowledge, the DW pumps I have seen do not have any form of check valve in them but I certainly would defer to Mr. Maytag if he/she is among us.

Eric S.