Water Overflow

Hello All,

I have a problem where my sink and washer machine connect into the same line and if I run both at the same time the washer machine will overflow where it enters the system. The pipes drain into a dry well. I bought the house like this and haven't done anything to this plumbing. When I had the inspector come through before buying it he made a comment about it not being to code or something but did not go into detail. I am hoping I can modify the system to keep the overflowing from happening. Does anyone have any input on how I can fix this problem? I am thinking it might have something to do with the location of the vent pipe or the size of the pipes. I looked down the clean out location to see if it was clogged at all and it was not. There are no issues if I run the washer machine or sink by themselves. Please see the attached picture for the set up. Thanks for your time, Kevin.

I believe a back siphon problem can occure leading to dirty water into cw.also i belive the code book says a minimum of 18 inches of vertical pipe is required before the p trap .also the vent dosent look right but im not experienced enough to give out my output on that.but hopefully some good plumbers here can teach us .

I don't know code in your area, but in mine, all fixtures must discharge either to a public sewer system or a private septic system. The standpipe on a laundry drain must be a minimum of 18". Each connection to the sewer or septic (for this one we will call the drywell a septic system) must have a vent to the outside air. The lack of any of these requirements could be causing your problem.

For starters i would drop the sanitary tee as close to the elbow as you can,then install a longer standpipe

Hey thanks for all the input. Current code doesn't allow the use of drywells in my area. I do have a septic system but the drywell was grandfathered in. If I have to do any major plumbing I assume they would force me to tie into my septic system. I don't really want to do that because that too isn't to code because it is too small and I don't want to be adding more water to that system. So I was hoping there was a simple solution to fix this problem. I will try extending the standpipe first to see if that helps. The vent also doesn't vent to the outside air, there is a redi-vent by Studor attached. Which is some sort of filter. Don't know what the requirements for those are. But I imagine if it is clogged it would cause issues. I don't think it is though because I feel like if it was clogged then I would have issues any time I used either my sink or washer and not only when I used both at the same time. Thanks again.

So I lengthened the stand pipe to the 18". I was going to make it longer but 18" was the max I could fit in that location. Anyways this appears to have fixed the over flowing problem. So thanks for the help. At some point in the future the whole septic system and plumbing will be redone but at least for now my basement won't flood. Thanks again!