# Garbage Disposal Backup



## handymansol (Feb 1, 2007)

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.


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## Ron The Plumber (Oct 10, 2006)

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


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## handymansol (Feb 1, 2007)

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


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## gitnerdun (Nov 1, 2006)

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


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## Ron The Plumber (Oct 10, 2006)

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.


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## handymansol (Feb 1, 2007)

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.


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## JamesNLA (Jun 2, 2006)

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


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## Ron The Plumber (Oct 10, 2006)

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.


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## gitnerdun (Nov 1, 2006)

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


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## handymansol (Feb 1, 2007)

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???


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## tzzzz216 (Dec 25, 2005)

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 !!


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## Double-A (Jul 3, 2006)

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?


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