Plumbing question

[Battis]

The washing machine is in the kitchen, about 15' from the kitchen sink. We replaced the double sink (with garbage disposal) with a single large sink (no disposal). The sink and washing machine each have a vent off the traps. The sink drain used to meet the washing machine drain directly below in the basement, then they traveled approx. 30' to the main drain.
Since we replaced the sink, when the washing machine does its first spin cycle (and only the first spin cycle), the water in the sink trap gurgles and bubbles. So, I split the drain connection in the basement, and ran a separate pipe from the sink drain about 25' further down, where it again meets with the washing machine drain. I replaced the washing machine drain pipes that were 1 1/2" with 2" pipes. I cut out and cleaned approx. 25' of washing machine drain (no clogs).
I'm guessing that the washing machine is creating a vacuum that sucks at the sink trap. Other than running a complete separate line for each to the main drain, is there any way to keep the washing machine from creating that vacuum that backs up close to 30'?

[Winger Ed.]

You might consider a vacuum breaker/vent that mounts on top of the sink in the hole for the little sprayer,
or one could go along the line somewhere.

I had to do that with a dishwasher, and they use a fraction of the water a washing machine does.

Water swishing noise is normal.
Air gurgling is telling you it needs a vent, or something is clogged.

[Preacher Jim]

Try cleaning your vent slack mud dapper and birds can stop them

[Battis]

I'll check it out. The washing machine drain pipe in the basement has a cleanout. Last week I opened the cleanout for a second during the spin cycle and the gurgling stopped.

[Battis]

What's the best way to clean the vent (other than calling a plumber). If it was the vent wouldn't there be problems in other parts of the house?

[MT Gianni]

Use a sewer rod down through it from the roof. it can be a steel 1" tape with a roller or a 3/8-1/2" cable powered by electricity. See a good rental shop. First though, stand on your roof with a mirror and see if you can see all the way down it. If it is a 1 1/2" line connected to a 2" washer line not much but the vacuum breaker will help it.

[BD]

Trouble is with the sink vent. See if you can clear it. If not, a Studer (sp?) vent for the sink should alleviate it. T off after the sink trap and mount the studer vent as high under the counter as possible.

[Battis]

Might be time to call in a pro- the house is a big old 3 story Victorian with a crazy pitch to the roof. Me and heights don't get along.

[Battis]

The vent under the sink is fairly new. So, that vent should open when the washing machine pulls at it? When we had the double sink, this did not happen. Could it be that air was pulled from each sink?

[tinsnips]

Try an auto vent on the wash machine drain line make sure it is above the water level of the washer.

[Battis]

This is what's on the sink (under the sink) and also on the washing machine.
https://www.plumbingsupply.com/autovent.html#trapvent

[NyFirefighter357]

Remove your clean out plug & a tee, re-install your plug, add a piece of pipe to the top of the tee and install an Oatey 39017 SURE-VENT AIR ADM VALVE.

https://www.mobilehomerepair.com/plumbing-check-vent-counter-sink/

[Battis]

The pipe that the vent sits on under the sink drops straight down into the basement. I tried removing the vent from the top of the drain pipe but the sink still bubbled. In the basement, the drain pipe drops down from the washing machine, and goes into the 2" pipe. Here it turns 90 degrees to the right and travels to the front of the house and into the main drain. There's a 3 ft section of pipe that extends to the left of that connection that has a cleanout at the end. I'm wondering if I can add a vent in the basement at the cleanout.

[popper]

Possibly the disposal was the vent, now gone?

[Battis]

I was wondering about that.

[NyFirefighter357]

You need a vent like I posted under the sink & if you hard connected the washing machine drain hose you need one there as well.

[Battis]

This is what I did. Under the sink there's a mechanical vent on top of the pipe that led from the trap. Off the washing machine there's also a mechanical vent on top of the pipe that led from the trap. I removed both vents (cheap vents - under $5.00 each and fairly new) and ran the machine. It didn't gurgle in the sink. Now I have to figure out which vent was failing. But this is what I don't get - here in MA, apparently those vents are not legal anymore, and if a plumber works on your pipes, they will remove those mechanical vents and cap the pipe. How, then, do you vent the drain pipes?

[BD]

"I tried removing the vent from the top of the drain pipe but the sink still bubbled." If the vent is installed downstream of the sink trap, it's hard to imagine how this could be happening. With the pipe open to the air there should be no way that water from another appliance could make the sink trap bubble.

[Battis]

From the back of the house forward to the main drain, it's the sink first (with a vent), then the washing machine with a vent. I changed the washing machine drain to 2" (from 1 1/2") then I ran the machine with the sink vent off, and sure enough, the sink did not gurgle. Put the vent back on and the sink gurgled when the washing machine ran. The vent seems to open and close with light pressure but it's a cheap vent, so I hope a better one will work.
I'm waiting for a plumber to get back to me. From what I understand, by code, the sink and the washing machine have to be vented through the roof. But at least the gurgling has stopped (when I remove the sink vent).