Expert: Sharon McCarthy - 10/21/2009

Question
I have a house in the country with a septic tank when the washer drains the toilet gurgles what could cause this?

Answer
Dear Bill,

  All smaller drainlines "tee" into the main line going out to the septic tank or sewer. Generally they tee into the closest toilet lines under the house, then the toilet lines merge into one main line.

  When the washing machine drains, the pump pumps out 20 to 40 gallons of water within a few minutes. This is a large load of water. Washing machine drain pipes are usually 2" pipes by code, large enough to take that amount of water that quickly. The water then dumps into a larger line that goes from one of the toilets.

  If there is a partial blockage in the toilet line PAST the tee where the washing machine line connects, all the water rushing out from the washing machine can't pass that blockage and the water will back up, but it will back up into the toilet line.

  All pipes are going downhill. The washing machine pipe is going down at an angle to the larger toilet line and enters that pipe through a tee. Once that washing machine water enters the larger pipe, if it can't all flow out because of some obstruction in the pipe, it will follow the easiest route BACK.

  This is only to explain how this works. If this blockage gets larger the toilet might begin to overflow when you use the machine. Right now, the blockage is still allowing some water through. If you have clean-outs outside your house, you may have to run a snake through the main pipe to remove what's in there.

  I'm very familiar with septic systems. Sometimes the pipe from the house to the tank can crack and roots will get in. Sometimes something went down, like some paper towels, a few tampons, a sponge that went down the toilet with dirty water, anything like that, and the object will get snagged up at a bend or where the pipe enters the tank.

  Another reason, sometimes there are a lot of solids floating in the tank, an accumulation of grease [which will turn into white chunks in cold water] and other material that doesn't decompose quickly. This floating debris can prevent waste water from dropping down into the tank. Do you add bacteria to your tank regularly? You might also try that, a bottle of septic charger which you can buy at any hardware store. It's full of anaerobic bacteria, just what the tank thrives on.

  These are the most likely causes. Good luck with this!  Sharon