Laundry pump sends some of the water up through second floor bathtub drain

2 story house with basement. Septic tank connected to a branch with two arms, each of which is connected to a dry well. When the laundry pump in the basement fires it is fairly common for drain water to come bubbling/gurgling up through the second floor bathtub drain. Gurgling can sometimes be heard at other house drains, but the upstairs bathtub is the only one that takes on water. Any suggestions on figuring this out? My wife loves taking baths and she hates it when dirty drain water comes along and interjects itself into her clean bath water... Can't say that I blame her!

 

When was the last time the tank was pumped?

 

Washers dump a lot of water fast. Sounds like a partial clog in drain line someplace.

 

I agree, I would first be looking for a clog but getting the septic tank pumped will not hurt. If you get the tank pumped first run a load of laundry and see if the water backs up into the tub. If it does then it confirms that you have a clog or plumbing problem. If it drains fine then you've got bigger problems with your septic system.

 

Curious about the term "laundry pump" in contrast to "clothes washer"...

Is this a basement laundry where all the water from the wash cycle accumulates in a plastic 55 gallon drum, then a sump pump empties it all into the main drain?

Here's a wild guess - older house with additions, the 2nd floor bathroom is the original from when it was a 2, 3 or 4 bedroom house with 1 full bath? Then other bathrooms were added over the years?

 

3.5 years ago.

Generally speaking, yes. If you want the details, go read this thread from me from a few days ago. That'll tell you the old setup and the new setup.

House was built in the mid-to-late 1960s. Not positive on the additions, but I don't think so. I think the whole house as it currently exists was built at the same time. 2 bathrooms - the 1 full bath upstairs, and 1 half bath on the first floor. Both bathrooms were re-modeled by the previous owners 10-15 years ago. There's an AAV in the wall cavity behind the bathtub in the upstairs bath. I'm hazarding a guess that the original bathroom config from the 60s didn't include an AAV. Not sure what the remodeler changed with the piping config but I've wondered if he messed something up somewhere along the way.

In 2011 or 2012 we had drain line blockages outside. The pros we called out found that tree roots had penetrated both the drain line and existing old septic tank. At their suggestion we had the old septic filled in and a new larger one installed. Pretty sure they ran new drain line from the front of the house patio to the new septic tank. Then we had the septic pumped in August 2015. Based on that pumping interval it seems likely that we'd be due now, although we did have more people in the house back then - 7 back then; 5 now.

 

Trip the laundry holding tank pump and then don't do laundry when taking your bath. That will prevent dirty water from coming up the bathtub drain.

Are you absolutely, positively, sure?

If not, find out for sure. Some drain plumbers have video probes they can put down the drain.,

Dig up and open the septic tank hatch. Normal water level after no one has been using water for a few hours is roughly 9 inches below the underside of the septic tank lid. Especially if the septic tank is really full then you have problems with the dry wells (or leach field) and the pipes going there.

 

True. And that's what we generally try to do but every now and then we forget.

What's typically involved with opening a septic tank lid? When they put the new septic tank in they installed "risers" so there are access covers at ground level. I've never removed one of them so I have no idea what's underneath. Presumably an open cavity down to where the actual septic tank lid is. Is it opening it up something I could theoretically do in 20-30 min tomorrow morning before I go to work? I have a plumber/drainage pro scheduled to come out tomorrow afternoon, but if I could check the septic and see if it's full myself and start by getting that pumped that might save me a bit of money in the long run. And if the septic tank is really full how can I tell if it's because of dry well issues or just because it's overdue to be pumped out? Is it that needing to be pumped out will be full of solids up to the top, whereas drain field issues will have water at the top?

 

If you have risers then there is less digging you need to do in order to access the hatch lid.

The normal resting level for the liquid in the septic tank is somewhere around 9 inches below the underside of the lid, even if the septic tank is a little overdue or even somewhat overdue to be pumped.

A layer of foam on top does not count as additional liquid height within the septic tank.

Septic tank technicians should be able to tell you whether the tank is really in need of pumping. Normally the septic tank is ready for pumping when solids have accumulated on the bottom up to a third of the tank depth.

If the septic tank was full to the brim and stayed that way for hours then the leach field or dry wells beyond need to be inspected for problems. The problem could be as simple as too much rain in the past few days but even so, if that caused the septic tank to stay completely full, your septic system is not performing as well as it should.

Pumping a septic tank a second time in quick succession is a waste of money unless you need the tank empty for inspection/repairs or you are waiting for repairs to the dry wells or leach field and you needed to temporarily change the role of the tank from septic tank to holding tank. Nothing exits the septic tank for the leach field until the liquid level get back to the 9 inches below the top.

 

Allan -
Do you mean "below the bottom of the riser" not below the underside of the lid?

 

Below the bottom surface of the top of the septic tank itself, namely leaving an air pocket 9 inches thick that may have some foam occupying that space.

 

Thanks guys! Turns out it was a lot of blockages in our main cast iron drain pipe. The guys said it's pretty typical for cast iron drain pipes over the years; they tend to get clogged up a lot more quickly than drain pipes of other materials. They got it cleaned out and the problem seems to be solved now. No more water in the upstairs bathtub when the laundry pump runs.