First, thanks in advance to anyone who offers up advice. I'm a relatively handy guy who likes to tackle things myself. I've owned a 60 year old rental property for two years. It's an old house chpped into six one b/r units and recently one of the tenants passed away after living in her unit for 20 years.

While painting the unit I noticed gurgling noises that came from her bathroom whenever the laundry machine almost directly below it was run. The tenant was relatively deaf and understandably, never complained about this noise.

Separately, I noticed that the bathtub drain was relatively clogged. After an incredible abount of effort with a 25 foot snake and a couple plungers I got that drain unclogged. The gurgling noise remained.

The laundry machine below the bathroom drains into a utility sink which has a sump pump below it tied into a drain line in the ceiling below. Most of the time a lint trap is tied on to the end of the laundry discharge hose, but it does fall off occasionally.

I've tried snaking the different vent stacks and drain lines in the house with a 25 foot snake. The one closest to the bathroom was on the roof maybe 5 feet above the ceiling in the bathroom but was offset roughly 15 feet.

At one point I had the bathroom sink trap disconnected and had it plugged with a paper towel to keep the gasses out of the apartment while I replaced it. When I got back the next day the paper towel had been blown out of the pipe.

Based on my own research and thinking confirmed by a guy at Home Depot who seemed knowledgeable, I bought an air adminttance valve and put that below the sink trap hoping that the gurgling noise was caused by a vacuum created when the large amount of water was drained out by the sump pump during the drain cycle of the laundry machine.

Seemingly, this did not fix the problem because when I was signing the lease with a new tenant last night, the gurgling noise returned! I need to fix this issue pronto because she is moving in later this week.

Any idea what the problem is if all the drains in the bathroom work no problem, but the gurgling continues in this one bathroom? No other tenants (and they all have their hearing) have had any issue with noise or draining.

Thanks,
Trevor

Hi Trevor,

I take it that this is a two story house and that you are snaking from the roof vents. If that's so the 25 foot snake you are using is next to worthless.
You need a commercial sewer machine, to reach the blockages. That 25 footer's good for going through traps but to drop a cable from a roof vent to the base will eat up almost all of it. Your statement that you still have a gurgle tells me that you still have a blocked vent and that the system's attempting to vent through a trap and your statement about The paper towel plug you placed in the open lavatory stubout tells me that you have a blockage in the drainage that sets up a bubble,(blowback) situation.
All in all what you should do is to buy or rent a sewer machine and redo the vents and drains. Good luck, Tom

The plot thickens. I had a rooter guy out to the apartment house and he snaked the main drainline after where the sump pump is cut into the copper drain pipe. He didn't find any major blockage and the gurgling noise still happens in the bathroom above.

This rooter guy did notice a one way valve that was put in place to keep the sump pump discharge from backing up into the bathroom. He shared that the noise is likely the first bit of the big sump pump discharge going past and closing the one way valve and then a second gurgle happens when the little water is let back through the valve after the main discharge has finished running its course.

Does anyone have any ideas on how we could lessen the noise further? Should I try removing the one way valve to see if the pipes can handle the backflow and the noise is reduced? Would a second one way valve in the drain riser for the sink reduce the noise? Are there newer one way valves that stay closed until water opens them?

I have spent $100 and still have the tenant moving in later this week! All advice is appreciated.

Thanks,
Trevor

Hey Trevor,

I went back and studied your complaint and at first I was thrown off by one word, "gurgle". Now a gurgle is caused by suction, ie; a trap acting as a vent and the noise heard is the air being sucked through the water in the trap seal.
I should have snapped to what was happening when you said," At one point I had the bathroom sink trap disconnected and had it plugged with a paper towel to keep the gasses out of the apartment while I replaced it. When I got back the next day the paper towel had been blown out of the pipe."
"Blown out of the pipe" clued me in.
Ya don't have a "gurgle" caused by faulty venting and I don't for a minute think the check valve in your sump pump caused it.
No Sport! Ya got a "bubble". The reverse of gurgle. And this bubble of air is caused by the forceful entry of the washer discharge being pumped into the drain line and pushing the air out of the water seal in the lavatory trap.
Of course the AAV didn't help. It can only vent air in and not out. Try this, remove the AAV and cycle the washer while holding your hand near the open hole, no "gurgle" but a lot of air coming out? I'll wait with baited breath for your answer. God! I love it when a plan comes together!

Speedball,

Thanks for the expert advice. If we assume it is a bubble and not a gurgle, is there an easy fix? I would enjoy applying a fix just after confirming your hypotheses while I am at the property next.

My do-it-yourself guess is that my vent pipe became undersized when the laundry machine/sump pump was added. I've got some ideas on what might fix the problem but I'm smart enough to listen to the expert before I make any suggestions!

Thanks,
Trevor

You mention a sump pump but I don't see any mention of a holding tank. The problem that you have is addressed by a dedicated vent from the holding tank to the roof. Unlike the drainage vents in your system this vent "breaths" out as well as in to vent the bubble of air caused by the discharges pressure from the sump pump. This is why it's a dedicated vent with no connection to the other vents. Do you have such a holding tank? If so then the dedicated vent is clogged and must be cleared. Once cleared the problem's solved. Good luck. Tom

The laundry machine discharges into a normal height plastic utility sink. The sump pump is located beneath it and is housed in a black plastic housing which must also act as the holding tank as quite a bit of water drains from the utility sink before the pump kicks on. The plastic housing is roughly 14" x 12" x 12". I don't recall two discharge tubes but I haven't crawled under the sink. The sump pump definitely could be clogged in some fashion since the filter net for the laundry discharge hose sometimes falls off and stays off for several days until I catch it. I'll disconnect the sump pump to take a closer look.

It might be a couple days before I can do a proper investsigation.

Thanks again,
Trevor