Garbage Disposal Backup

handymansol

I had a tech install a garbage disposal the other day. Everything went fine. 2 days later customer is calling to tell us the disposal is backing up.

We go out to snake the drain - 20' and all is clear. Disposal still backsup and only when you turn it on. So we go and return it and get a replacement. Same thing happens.

Not sure what is going on - I've only seen this happen one other time and we referred them to a plumber.

Any Ideas would be helpful.

Ron The Plumber

How are the pipes under the sink, how is all plumbed together?

handymansol

New trap. Dishwasher connects into disposal direct and trap exits to drain pipe.

gitnerdun

Is the water backing up in both compartments or just the disposer side?

Ron The Plumber

Double bowl sink? Does disposal tie to a tee under sink before trap? If so is this tee a baffled tee?

Lots of questions asked to get to the problem at hand.

handymansol

single sink, someone else said it could be the power of the disposal, but that doesn't jive.

Prior garbage disposal work fine - just noisy and customer wanted a quieter one.

Dishwasher also drains fine. Water drains when disposal is off. The backup only happens when the disposal is running.

JamesNLA

I hate to ask, but did you remove the DW knock out?

Ron The Plumber

OK one more question, what is the horse power, higher horse power disposals have a splash guard insert that goes into the top, running a higher hp disposal without will cause water to expel out of it, making it appear to be backing up.

gitnerdun

20 feet may not have been far enough. Go farther.

handymansol

Okay to answer all the questions posed (been a busy day today!).

Yes - Dishwasher knockout is open - the dishwasher is not backing up - it is the drainage exiting from disposal. See my note about dishwasher draining properly through the disposal.

Not sure what the hp is on the disposal - will check on splash guard and hp.

Snake 20 feet or more? May be a problem, but if water drains without the disposal running then I eliminate that possibility, not to mention other sinks in the house off the same main drain are fine.

The other thing I was thinking was something with the venting - maybe putting an admittance valve under the sink - maybe the water isn't able to drain because the disposal is creating an unnecessary vacuum???

tzzzz216

How soon does it back up , right away ? Have you checked the arm coming out of the disposal into the tee , Do you have a seprate vent for the disposal , which is required now at least here anyways ?





The only easy day was yesterday !!

Double-A

Sounds like a venting problem, but I would not install an air admitance valve. Did this installation have a disposer before? How old is the house? Lead drains to kitchen sink? Is the sink plumbed with a 1/4 bend, then an 1/8 bend down to a wye at the vent? Have you checked the vent on the roof?

__________________
"My clients’ wishes are the center of my attention." -- David Guido, a contractor in Woodstock, N.Y.
New York Times, July 20, 2006