My wash machine drain line will back up when I run a smaller load where the clothes don't saturate most of the water in the tub. Larger loads don't tend to overflow it. I've checked the p-trap and it's clear. I have a cleanout right above the drain inside the house but as usual, it's old cast iron and the cap won't come off without inevitably breaking it. I know newer machines have very strong pumps and the drain pipe rises to about 4ft but it still will back out. I'm guessing i have years of crap obstructing the line but before i get a plumber, has anyone else dealt with this and has some insight on what they found?

ETA: i'm finding this is more of a common problem as i read and watch youtube videos. Some people have attached/retrofitted anywhere from 2-4in PVC above the p-trap to let the water have somewhere to sit until it drains. It's an option but i still wonder if i have a clog because this wasn't always happening.

This post was edited on 9/19/22 at 2:03 pm

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Posted by SurfOrYak

BR/MsDelta

Member since Jul 2015

403 posts

Posted on 9/19/22 at 1:56 pm to cberni1

When the drain pipe fills up, does it then drain off quickly or drains off very slowly? Having the same issue, but mine drains off very rapidly after filling up. I think my issue is high flow on drain pump—I have a Bosch front loader. Plus, I snaked everything and got no obstructions. About to partially obstruct drain hose to slow it down. They claim that won’t hurt the pump.

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Posted by weadjust

Member since Aug 2012

15152 posts

Posted on 9/19/22 at 2:40 pm to cberni1

quote:
it's old cast iron

My house was built in 1974. I had the same problem and had to replace my rusted out 2" cast iron washing machine and kitchen sink drain lines. Busting up the slab was a mess. I would try one of those jetters from amazon you attach to a pressure washer first.

For several years before I replaced the cast iron pipes. I used a fernco reducer and hose clamps to prevent the stand pipe from overflowing. The washing machine pipe backup was forced into the kitchen sink.

I hope your cast iron pipes aren't toast