garbage disposal overflow to other sink

I replaced a garbage disposal 1/2 hp, Insinkerator Badger 5) under a double-sink. I would like some help determining how to prevent water backed up over other sink when in use.

With the stronger disposal (1/2hp vs. old 1/3hp), the water could not drain to the main pipe (through P-trap) and some popped up other sink. When I removed the Air Admittance Valve, problem went away.

How can I fix this problem? Your assistance is greatly appreciated.

boDoanh said:

I replaced a garbage disposal 1/2 hp, Insinkerator Badger 5) under a double-sink. I would like some help determining how to prevent water backed up over other sink when in use.

With the stronger disposal (1/2hp vs. old 1/3hp), the water could not drain to the main pipe (through P-trap) and some popped up other sink. When I removed the Air Admittance Valve, problem went away.

How can I fix this problem? Your assistance is greatly appreciated.

Click to expand...

The problem is the lack of a proper vent. The unit is causing a positive pressure in the drainage line which is the issue.

You didn't happen to put the tailpiece in upside down....don't know if it's possible but if it worked before and doesn't work now.

drain

There are many possible causes an obstructed drain being the first option, especially since removing the AAV eliminates the problem. Or there might be a missing baffle tee, or.................

hj said:

There are many possible causes an obstructed drain being the first option, especially since removing the AAV eliminates the problem. Or there might be a missing baffle tee, or.................

Click to expand...

I skimmed over and missed the AAV part. OP - your AAV may be bad, try to replace it.

SewerRatz said:

The problem is the lack of a proper vent. The unit is causing a positive pressure in the drainage line which is the issue.

Click to expand...

Yes, I think lack of proper vent is the problem. When I remove the AAV, problem goes away.

The pipe goes from the disposal into side of a T (other sink goes straight down into top of the T), other end of the T goes to a P-trap and out to the main pipe which an AAV is installed.

I didn't have this problem with a weaker 1/3hp waste disposal.

The drawing below has the p-trap weir reversed. This creates too deep a seal. The outlet from the disposer should have been straight, and the 90 not used. Whoever made that drawing, doesn't know how to plumb. Terry

Click to expand...

Most plumbers would have used a disposer kit, straight from the disposer into a baffle tee.

Is the drain partially plugged? A Badger V isn't a particularly powerful disposer - it should handle a 3/4 horse disposer just as easily. And I have no idea why removing the AAV would make any difference. If the drain can handle the discharge, even a complete absence of a vent shouldn't make a difference.

Does the kitchen drain connect to a larger pipe under the floor, or does it go out to a drywell? If there is pressure resistance in the pipe there is bound to be a problem somewhere in the line. For example, it might have a swale in the pipe that is full of water. Or it may be that it's mostly plugged and the water goes through very slowly.

I'd fill both sinks to the top without running the disposer and see if they drain quickly.

The drawing below has the p-trap weir reversed. This creates too deep a seal. The outlet from the disposer should have been straight, and the 90 not used. Whoever made that drawing, doesn't know how to plumb. Terry

Click to expand...

Not only that but all that tubular 1 1/4" pipe will be holding water to the level of the dirty arm.