Garbage Disposal: Dual Sink, Non-disposal side spits up

[Q]

Hey all. Tried searchin the newsgroups were something on this but found no exact matches to my problem. Have a dual sink with a disposal attached to the right. If the right is slightly clogged with food and water, I flip on the disposal to clear the drain but the left side sink spits up like a geiser almost if I dont turn it off in time. The stuff that comes out the left is the stuff that goes thru the disposal I think. Not sure on the specifics of how a disposal works but is there a drain. Is there something I can do that doesnt risk me damaging something worse (ie:should I call a plumber) or will a bottle of drano fix this right up. Oh and if the disposal side is fine and draining and theres just water running, the left side doesnt fill up. Its only when I run the disposal does stuff get pushed up the left side. Thanks.

[John McGaw]

I have had similar occurances and every time I did it was the result of a partial blockage past the point where the left drain and the disposer "Y" together. It seems to happen because the disposer "throws" water forcefully which can't get past the blockage fast enough while regular flow has no problem doing so. I set up my plumbing so that there are seperate "P" traps for each side which means drain cleaner in the system would never reach the site of my clog. If yours is plumbed so that there is a single "P" trap I guess it is possible that your blockage might be there and that drain cleaner might have some effect (but if it is that simple, removing and cleaning the trap manually would be easier and more effective).

[Speedy Jim]

To test if there is a blockage, fill one of the bowls with water. Let the stopper out and see if the water goes down rapidly and does not back up into the other bowl.

If it passes that test, look at how the 2 bowls are plumbed together. If a single trap, it can use either a "center outlet" with a TEE or an "end outlet" where one side drains staright down and the other TEE's in from the side.

Either type of TEE should have a baffle plate inside to direct flow. Check that it is present. The "end outlet" setup where the disposal discharges straight down is probably less likely to backup than the "center outlet" style.

Jim