When installing a disposal doe it matter if the drain line from the disposal is lower than the drain from sink? Will pressure move it on out? Does it have to have it's own trap or is it OK to run it above the one trap that is already in. I am planning on running the dishwasher drain into it as well and do I need to put an air gap in the line? If so, where should it be located? Thanks

"When installing a disposal doe it matter if the drain line from the disposal is lower than the drain from sink? Will pressure move it on out?"
The disposal MUST be higher then its trap for it to operate properly.

"Does it have to have it's own trap or is it ok to run it above the one trap that is already in?"
We wye off at the stubout and run a separate trap for the disposal and if there's a double compartment sink we tie the two tubs together with a continuous waste discharging into its own trap.

" I am planning on running the dishwasher drain into it as well and do I need to put an air gap in the line? If so, where should it be located?"

E don't use mechanical air gaps in my area. We form a air gap with the discharge hose. : Your drain hose MUST be looped higher then the flood rim what you are discharging into. All that means is when you run the line, strap it up so the loop is above the inlet of the disposal or whatever you are draining into. If this is not done the water that you discharge from the sink will drain back into your dishwasher. Use a 3/4" copper pipe strap to secure but a nail and some wire wil;l work also. Some models may have an outlet attached to the top, but most of them will have to be strapped up.
Good luck, Tom


Your drain hose MUST be looped higher then the flood rim what you are discharging into. All that means is when you run the line, strap it up so the loop is above the inlet of the disposal or whatever you are draining into. If this is not done the water that you discharge from the sink will drain back into your dishwasher. Iuse a 3/4" copper pipe strap to secure but a nail and some wire wil;l work also. Some models may have an outlet attached to the top, but most of them will have to be strapped up.

Speedball1 Thanks for quick response, Let me make sure I understand correctly. For a double sink I should run a separate drain for each back to where it come in from the wall. Each with their own trap. I can make a loop (like a drip loop?) for the dishwasher drain and it it is to be above the "flood rim" I'm not sure what a flood rim is.

The flood rim is the highest point of any fixture that would run over if you keep filling it with water. Just loop the hose up as high as it will go, secure it with a pipe strap and you have built a air gap. I've put up a image of a air gap. That's how the hose should look, only without the mechanical air gap.

We wye off at the stubout and run a separate trap for the disposal and if there's a double compartment sink we tie the two tubs together with a continuous waste discharging into its own trap. Sorry about the image. I'll work on it.
Good luck, Tom

See if this image comes out better.