We've never owned a dishwasher, but we would like to plan for one in our new house. We won't be installing it right away, but would like to install the necessary plumbing and wiring now so it's ready to go when we are.

Anyway, I'm curious what the "proper" way to rough-in a dishwasher is. Is connecting to the sink drain the only way to install these things? Or, can I install a dedicated drain for the dishwasher?

If I use a dedicated drain, can I share the drain and vent pipes by using a "Cross" pipe (double sanitary tee), with one arm going to the sink and the other to the dishwasher?

Thanks,

Anthony

You can use a dedicated drain for a dishwasher as long as it has its own trap and is vented correctly with local codes. As far as a common drain with the kitchen sink, How tall is this dishwasher?

> As far as a common drain with the kitchen
> sink, How tall is this dishwasher?

What's the standard? As I said, we've never owned a dishwasher, so I know practically nothing about them.

Anthony

anthony... if you are planning to have a garbage disposer in your new house, then the dishwasher will drain into the fitting on the side of the disposer. if not then you will need to install a branch tailpiece instead of a standard kitchen tailpiece. (the pipe from the basket strainer to the trap). for a hot water shut off install a dual stop. one inlet, two handles and two outlets. the common size is 5/8 compression inlet by 3/8 compression outlets. you can have the electrician dead end a wire in a box if you want. good luck...

If you put a garbage disposal in, you have to put in a air-gap as required by code to prevent back siphonage into dishwasher if sink drain backs up.


A tapped tailpiece on either basket strainer will suffice for you situation...about two bucks.


You can also tie into your hot side water line with a add-on saddle valve (not recommended) or cut in new tee and then put a straight stop on 1/2 X 3/8 compression, sweat or i.p.s. and run 3/8" copper to a 3/8 compression to 3/8 ips dishwasher 90.



All for about twenty dollars.

> planning to have a garbage disposer

We will NOT be installing a disposer now or in the future.

> you will need to install a branch
> tailpiece instead of a standard kitchen
> tailpiece. (the pipe from the basket
> strainer to the trap)

But, is there a way to install a dishwasher without tieing into the sink drain? I would prefer to plumb a seperate trap/drain for the dishwasher if possible.

I would think it would be done similar to a washing machine, but I haven't seen any reference to this type of installation.

Water supply and power hookups are easy enough.

Anthony

If the DW is directly next the KS, it doesn't make sense to have a separate drain and vent. Just tie it into the kitchen drain with a DW tail and be done with it.
If the DW is across the room, away from the KS, you need to install a trap and vent below the floor. Check with your local codes.

For those who like, a seperate p-trap can be added either behind the dishwasher or under sink cabinet. (exposed) The plus side to having a seperate drain for dishwasher is the noise when the dishwasher drains would not be heard as much. I've seen it done like this in very pricey condos and in older installations. GOOD LUCK

The logistics of a separate drain usually make it less desirable than connecting it to the sink drain. You have to have a separate trap and an air gap on the counter top would be required. Next you have to make a watertight connection between the 1 1/2" trap and the 3/4" hose drain from the air gap. The trap has to be above the floor, in a location where it can be unplugged in the event of a stoppage. That trap could be connected to the opposite side of the sink connection as long as it was done properly. The noise of drainage would not be much less since you would still hear it passing through the air gap.

Hello hj - I understand the air gap theory but it is rarely installed for a DW discharge. What is accepted here is that the DW discharge hose must extended to the highest point under the sink cabinet, basically touching the under side of the sink, then loop back down and tie into either a DW tail or the disposal. The hose must also be secured so it will not sag. It is a not 100% protection of contaminated water from a clogged sink backing up into the DW, but in most cases it does do the trick.

I was referring to the installation where they wanted it to have its own trap. That would need an air gap.