Kitchen sink w/Disposal

[Kameleon]

We have the standard stainless double sink with a disposal on the right side drain. The P-traps drain into a galvanized pipe which goes into the old style cast drainage. The house is about 40 years old and we have a well and I have installed a whole house filter due to the sandy soil that comes up from the well.

We use the disposal quite frequently, but about every 3-4 months, when we turn on the disposal, it will come back up the left hand sink drain and it has the appearance of black dirt and smells of sewage.

Not a lot to go on, but I have tried snaking it out and the snake gets to a joint and only that far. We have tried the drain cleaners off the shelf and even tried baking soda and white vinegar because somebody said they do that and it works.

Any thoughts?

[mdshunk]

There are drain clearing tools available at some of the big box stores that you hook on to a garden hose. The tool looks like a rubber bladder, and you insert it into the drain where you would your snake. When you turn the hose on, it expands the bladder making a seal and it injects full pressure from the hose down the drain. This tool has been very effective for me in the past, but I assure you that it will also find any weak joints in the drainage system.

[Kameleon]

I forgot I had that in the garage! Hopefully there won't be any weak joints down the way! :D

[DUNBAR PLUMBER]

If you don't have any success with the clog, remove all the galvanized piping to the cast iron and replace it with PVC, you probably will not have anymore problems with the system from that point on since it drains into a larger cast iron drain.