Can the garbage disposal outlet be lower than the building drain inlet? [duplicate]

Question

As shown in the diagram below, my kitchen sink garbage disposal has an outlet (#1 on diagram) which is about about half an inch lower than the inlet for the building drain pipe (#4 on diagram). Is this a problem and is there a way to remedy it without cutting out the wall to lower the building drain inlet? When I look down the sink into my garbage disposal, I see about a half inch of standing water which I suspect is related.

In the diagram:

1. garbage disposal (AKA disposer) outlet
2. P-trap inlet
3. P-trap outlet
4. building drain inlet (AKA the drain pipe coming out of the wall)

Answer 1

You are correct to think that the standing water in your garbage disposal is related to the inlet being lower then the outlet.

Water flows downhill... It doesn't flow uphill (excluding siphoning, which won't happen due to the vent near the inlet).

Your sink can only drain water until the water level is at the height of the inlet. Which is why your garbage disposal remains half full of water.

There is no way to fix the problem unless you either:

a) increase the height of the garbage disposal outlet, you can achieve this by buying a shallower sink, getting a shorter garbage disposal unit... etc..

b) lowering the height of the inlet. This will require you to cut into the wall... It is not as scary as you think. Just be careful and slow.

Answer 2

The simplest and cheapest way to proceed would be to remove the disposer and plumb without one. Food scraps would go into the garbage or a compost heap.

I removed our disposer 40 years ago and we have no problems. Our food scraps go into the trash/garbage which is collected once a week.

Normally the higher end of the P-trap is on the sink side so no water is standing on the sink side of the P-trap or on the drain side. No water standing in the horizontal runs on either side of the P-trap.