Plumbing Fittings Question:

The washing machine line could be connected to close to the "suds rinse zone", meaning the washer waste ties into the waste or soil line of another fixture to close downstream from the problem fixture. What is happening is the water is rushing by the suds at a high velocity, pushing ahead of the suds. Because the fixture is the closest place of relief, the suds will come up into the fixture, even a toilet. The code requires that a washing machine, kitchen sink, shower, and dishwasher line be connected at least 5' downstream from any fixture branch. This could be just one of many possibilities for the bubbling and backup.-Bill Dwight,