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hellonoko 09-01-2012 02:18 PM

How to diagnose / fix non draining disposal
I posted a bit ago but didn't get any replies so I am making clearer post.

My newer garbage disposal has stopped draining.

When you turn it on the water is pumped down the drains fine, unless there is a large amount of water in the disposal side and then it will back flush into the sink side.

I have included some photos of the drain pipes and a video of the sink in action.


The disposal is fairly new as you can see and a plumber who was doing work on the lower level of the house (this is the upper level) did snake the drain from the sink down recently.

What is the most likely cause of this problem and how can I diagnose it and fix it?


orange 09-01-2012 03:00 PM

I'm not a plumber, but my guess is you have some restriction in the drain line below the place where the garbage disposal and sink drains come together. I'd try snaking the drain line from below the sink down ward. If you have a sink or a clean out on the line at the lower level, I'd snake that as well.
Something is blocked between you GD/sink connection and the "street" or "septic" whatever applies.

Good luck.

joecaption 09-01-2012 03:04 PM

Just remove and clean out the trap and see what happens.
Make sure to put a bucket under it to catch the small amout of water that's going to come out of the trap.

hellonoko 09-01-2012 03:50 PM

@orange - I see what you are saying but the sink side never drains slowly. I just filled the sink with about 10 gallons of water and let it all drain and it all went down fine. I could hear it going down smoothly in the lower level (exposed construction) and it did not back up out of anything.

Wouldn't it need to be a total blockage to cause the disposal to not drain at all? It does not drain even slowly.

@joe - did as you said. nothing in the p trap, although about .5 gallons of water came out that was probably sitting in the line.

orange 09-01-2012 04:21 PM

Ok I see what you're saying - if it was further down the line, then sink shouldn't drain, but maybe it's draining slowly.

Further to Joe's approach, did you try snaking from the GD trap?

What exactly is the "plumbing" between the GD, trap and output from trap
to where the connection is with the sink drain?

oh'mike 09-01-2012 05:02 PM

Orange was correct----From the video--the water in the disposal sink backed up into the main sink----so the main sink drain is also a problem.

Rod both sinks well----if you have old iron and galvanized drains---that garbage disposer may cause you never ending trouble.--Your drains were not designed for garbage---only water.

hellonoko 09-01-2012 07:44 PM

@orange - the plumbing is as far as you can see in the photos and then.. who knows. its all inside those brick walls. below in the joist space its a single line that is then tied in with the dish washer drain.

They are not like in that diagram but I suppose I could alter them to be like that.

I did not try snaking from the garbage disposal trap as I have no snake but I will try that.

@oh'mike - I will get a snake tomorrow and try this out but I dont see how I can dump literally 7-10 gallons down the sink and have it train in maybe 20 seconds and then have the disposal side be not draining at all and have a problem past where they meet.

oh'mike 09-01-2012 08:17 PM

You will be successful-----it's surprising what crud lives in those old pipes and elbows--I would also suspect improper venting might exist.

An AAV (Air admittance valve or cheater vent) added to the disposer drain line might also be needed--they are cheap and easy to instal--so try the rodder (a small hand cranked one should work) first--then add an AAV if the slow draining continues.

Let us know how it work out---Mike----

hellonoko 09-02-2012 12:43 AM

Thanks I will try all this out.

Might it be a good idea to change my disposal drain to t into the sink drain rather than have it go into the wall as it does now and meet the sink drain there?

oh'mike 09-02-2012 07:08 AM

You need to rod the lines--I'd do that first and see if it works ---

if that fails--then consider reworking the pipes.

If the "in the brick' lines are junk---consider repiping through the bottom of the cabinet

idlplumb 09-02-2012 11:47 AM

Snake the drains. You have some buildup (probably grease and food junk) in the san tee at the wall or in the piping immediately following the tees. Chances are you're draining fine because it's draining slow but with the added velocity of the disposer, it can't keep up.

Can you fill the sink side and make a video of it draining until the very end?

hellonoko 09-02-2012 11:58 PM

I snaked both lines. The sink line worked fine. Got some grease type junk from the disposal line but no matter what could not get it to go more than a few feet down.

Ended up reworking the pipes. Thanks for all the help. Might have a plumber with a powered snaked give it a try at some point.

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