Washing machine drain line backs up

A. I have a problem with my washer drain water backing up into my double kitchen sink whenever the washer drains. I have been told to install an Air Admittance Valve, and I am not sure whether I should:
(1) install it under the kitchen sink
or
(2) I could simply connect to my washer drain pipe (with a sanitary "T" in the drain line, then connect a 90 degree elbow to this "T" and then attach the Air Admittance Valve to the top of the 90 elbow.

Any advise on this situation would be greatly appreciated.

Hi, Ross. Although they call it an air admittance valve, I think they also let air get out of the line so the water can flow through it. As such, I think the ideal placement would at the high point of the line.^^{[See entry of Jan. 18, 2012]}

Regards,

A. Our second floor washing machine began overflowing at the drain after a new pump was installed in the washer. Tried everything from snaking to the expensive camera down the line to find the issue. No problems, vent on roof was fine too. Augured down the line 75 feet to no effect.

What finally worked was installing a 45 degree piece of pipe to a y valve. The drain line now drops 2.5 feet to a trap, the trap comes up and the line goes about six inches across to the 45 degree piece then into the y valve where it connects to the vent pipe going up and also drops down into the wall of the house.

Jeff Stratton
- Ankney, Iowa, USA
December 10, 2010

A. The biggest issue with all of the above seems to me (or to be) that the volume of water used by older machines, is replaced by a larger volume of water used by the newer machines. Most of the pipes can handle the larger volume, but not at the same DISCHARGE as the newer machines. If you SEAL the gap from the machine to the drain line, eventually you have no air in the system.... eventually the water runs freely. While duct tape works, there must be a way to PLUG the drain hose into the line and seal it, solving all the problems.

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A. Most of the problems I have been reading here are due to improper plumbing connections and assemblies. The plumbing code specifically states that every trap has to be vented properly. Air admittance valves can work but do have the potential of failing. Location of the washer trap, height, length and height of trap arm and proximity of other plumbing fixtures, such as water closets and bathroom groups, can and do affect the performance of the washer drain. Only an experienced licensed plumber can identify if such plumbing drainage systems to be properly installed, either preexisting, altered or installed.

A. Like most people I have also had this problem and found out that the soap we were using had a waxy type substance that was visible on the soap fill area. What worked was using a bacterial drain cleaner .
which now I use a different soap and use the bacterial cleaner from time to time. Previous to this I put 170 degree water at full flow and the snake, the bacterial cleaner worked.

A. Hi, Cindi.

You need a professional plumber to look at this. Sad to say it could be very bad. Many 1950s tract houses used the least expensive, and often unproven materials like drain pipes that were essentially cardboard steeped in tar.

Regards,

A. I had this problem in my house 30+ years ago. the house was built in 1935 and had 1 1/2" galvanized pipe for a drain for the washer. I reduced it to a 3/4" pipe which fit snugly into the washer drain hose. I also "T"ed off it and put in a directional valve with a clapper in it, so that air could get into the line but water could not get out. This allowed the washer to pressurize the line and force the water into the drain system. It was easy to do and worked for about 25 years at which time I replaced all the plumbing while remodeling the kitchen. what I found when I removed the old galvanized and cast drain lines was really ugly! I could not even see through them they were so corroded. I replaced the washer drain with 1 1/2" abs and it works great.
If you use too much soap it can also fill the drain line with too much bubbles and the water cannot get past it as it should.
New washers use less water than the old ones did, but drain faster due to higher spin speeds.
Another problem I have seen that slows drains is blocked roof vents, wasps or birds building nests in them.

A. I want to thank all of you for your suggestions. I made a list of the ideas that I wanted to try before calling a plumber. 1. Lye, gel type drain cleaner 2. Enzyme type drain care, build up remover. 3. Power drill plus snake. 4.restrict drain water flow from machine. 5. call a plumber 6. buy a new front loader machine.
We bought a new machine 3 years ago and had no problems until about 6 months ago. We just recently noticed that the drain was overflowing into the crawl space beneath the house. I checked the drain hose by running a cycle and having it drain into a trash bucket. I knew then the problem was in the plumbing. Luckily, I was able to clear the drain using 1, 2 & 3. It took me a week and cost about $45. Don't give up. The enzyme type drain cleaner took 3 applications. I ran boiling water thru after allowing the enzyme type drain cleaner to sit overnight. The last thing I did was to run the power drill auger through and that pulled up some hair. Good luck !

A. Our drain problem has been solved!! We are so happy. My husband inserted a 1" pvc pipe into our drain hose before the drain pipe. It diffuses the water, slowing down the amount of water into the line. We haven't had water on the floor, since.