Gurgling Sounds in Washer Drain Pipe

[TexasDIY]

We live in a house that is a little over two-years-old and in the last year we have had a noise, when the HVAC is running, of gurgling in our wash machine drain pipe. The HVAC is in the attic directly above the washer and we suspect it drains into that line.

Several times we have gone into the attic, poured vinegar down the drain - followed after 30 minutes with water - and then blown out the line with an air compressor. The gurgling resolves, and then starts again in a few weeks. There is no water in the overflow pan.

We have noted a crack in the PVC elbow that allows a bit of water to pass. We noticed this when we poured vinegar down the drain.

We have also poured vinegar down the washer drain, followed by compressed air.

Appreciate all thoughts! Any ideas?

 

[Reach4]

Several times we have gone into the attic, poured vinegar down the drain - followed after 30 minutes with water - and then blown out the line with an air compressor. The gurgling resolves, and then starts again in a few weeks.

That is weird. Is this draining water from combustion, or is it just water from the AC?

We have noted a crack in the PVC elbow that allows a bit of water to pass.

That sounds worth discussing some more.

 

[Sponsor]

 

[TexasDIY]

That is weird. Is this draining water from combustion, or is it just water from the AC?


That sounds worth discussing some more.

Not sure - the unit is a heat pump. We *think* it's water from HVAC, but we've never had a heat pump before.

We plan on replacing that elbow as soon as the weather permits.

 

[TexasDIY]

That is weird. Is this draining water from combustion, or is it just water from the AC?


That sounds worth discussing some more.

I should also say the sound is when the heater kicks on. Not sure if it happens when a/c kicks on.

 

[Reach4]

Not sure - the unit is a heat pump. We *think* it's water from HVAC, but we've never had a heat pump before.

There is no water from combustion with a heat pump. The reason I asked is that water from a condensing gas furnace is acidic.

I am sure not picturing how you get a deposit that vinegar cures, unless your heat system has a humidifier fed by a water pipe. In that case, your house has hard water, and you could benefit from a water softener... solving this problem, and making your other house water better.

 

[TexasDIY]

There is no water from combustion with a heat pump. The reason I asked is that water from a condensing gas furnace is acidic.

I am sure not picturing how you get a deposit that vinegar cures, unless your heat system has a humidifier fed by a water pipe. In that case, your house has hard water, and you could benefit from a water softener... solving this problem, and making your other house water better.

I was told by HVAC installer that we would need to periodically put vinegar down that drain, so that's where we thought the issue was.

 

[Reach4]

I suspect you have a "bypass" humidifier up there. If so, you probably have a humidistat or a humidity control on your thermostat. I usually think of a humidifier as more of a thing where you have a conventional furnace, rather than a heat pump.

I suspect your house water is very hard. Still, I would not think clogging due to hardness deposits would happen in a matter of weeks.

City water?

 

[TexasDIY]

I suspect you have a "bypass" humidifier up there. If so, you probably have a humidistat or a humidity control on your thermostat. I usually think of a humidifier as more of a thing where you have a conventional furnace, rather than a heat pump.

I suspect your house water is very hard. Still, I would not think clogging due to hardness deposits would happen in a matter of weeks.

City water?

City water, yes. But it's not very hard. I'm in rural East Texas. But no humidity control on Thermostat

 

[TexasDIY]

As I'm researching youtube, wondering if this could be a venting issue.

 

[TexasDIY]

Found this with AI - wondering if anyone can lead me to a way to check this. The HVAC is in attic and I believe the lines run into the lines for the washing machine. No other pipes gurgle when HVAC cuts on. Also worth noting - our roof was replaced six moths ago.

"A gurgling sound from a washer drain pipe when an HVAC system turns on can be caused by improper venting or a clogged vent pipe. When the HVAC system runs, it can create a suction that pulls air through the washer's drain pipe, causing gurgling noises if the vent is blocked or improperly installed.234

The condensate drain line from the HVAC system might be connected to the washer's drain pipe, and if the P-trap associated with the HVAC unit is dry, it can cause air to be sucked back into the unit through the drain line, leading to gurgling sounds.25

To address this issue, ensure that the venting system is clear and properly installed. If the vent pipe is blocked, it may need to be cleared by a professional plumber. Additionally, running the HVAC system for a while can help fill the P-trap with condensate, which can prevent air from being sucked back into the unit.26

If the gurgling persists, it might be necessary to consult a professional HVAC technician or plumber to diagnose and resolve the problem."

Also saw that the p-trap/drain on a/c is dry and to add a bit of water. Will try that tomorrow, as we will have freezing temps through today.

 

[John Gayewski]

Can you draw a piping layout that shows how everything is connected? The condensate drain needs usually needs vented but gurgling in your washing machine pipe only when the ac heat runs is odd. It makes me think the gurgling is in the condensate line and cutting a tee in could help.

 

[TexasDIY]

Can you draw a piping layout that shows how everything is connected? The condensate drain needs usually needs vented but gurgling in your washing machine pipe only when the ac heat runs is odd. It makes me think the gurgling is in the condensate line and cutting a tee in could help.

I have no idea how pipes are laid out, but worth noting that while we know where the overflow drains outside of the house, we have never found the pipe outside if you blow water and air through line, which has us to believe it's connected to the line where the washer drains. The HVAC is above the washer in attic. There are two pipes coming out of the house in that location but never has there been anything that has come out of them.