Sink noise and HVAC heater....connection???

[prollins1]

Good morning,

I've lived in a newly built home for about 2 years. Today I noticed a popping noise from the pipes in one of the upstairs bathroom sinks. When I run water it disappears to return when water is stopped.

I've determined that the sink noise is related to when the upstairs HVAC runs. The heater turned on upstairs and the popping returned. FYI---when the heater cuts off, there's one louder pop and the popping stops!

Any solutions that I might be able to administer?....(I'm not a plumber...) The popping in continuous and is different than the sound that your pipes make when running hot water, expansion, etc.

Please help. My home is on the market to be sold and these noises could scare buyers.....

Thanks very much,

prollins

 

[Cass]

If it only happens when the HVAC is running it sounds like the room / house is so air tight that it is affecting the DWV system. Realy it is hard to tell not being there to inspect the problem. You could try and crack open a window and see it it happens when the window is open and the HVAC is running.

 

[Sponsor]

 

[prollins1]

Cass---I Opened Window......

......and turned on the heater. So far, no water pipe noises. Do I have to open the window every time now or is there a fix? First time this has happened after living here for over 2 years. Maybe something needs to be replaced....HVAC water valve, etc.

Can't thank you enough.

 

[prollins1]

Can Anyone Help Me???

Please see my previous post. Thanks!

 

[Mikey]

Good call, Cass...

prollins, does the noise come from the drain? If so, it's probably the trap clearing and gurgling. The culprit could be a leaking duct in the HVAC system (outside of the living space) that's allowing it to either pressurize or depressurize the interior of the upstairs, thus pushing or sucking water out of the trap. Could be something as simple as duct tape failing after a couple of years -- duct tape is no good for taping ducts. If all that is true, have all the ducts checked for leaks and fix them.

 

[prollins1]

Thanks Mikey...one more thing!

The gurgling is coming from the drain....however it hasn't gurgled in a few days now. But---whenever the HVAC is on upstairs, that same drain has a slightly mildewy smell from the air that emits from it that you can barely notice even in the next room.

With this in mind, do you still suspect duct tape? If so, where should I inspect the tape....up in attic where HVAC is located or somewhere else?

Big thanks for your help. My home is on the market and I need to nip in the bud ASAP.

BTW---Have a great Thanksgiving!

prollins

 

[Mikey]

Air should never emit from a drain unless you hear gurgling. Every drain has a "trap" associated with it that is basically a U-shaped section of pipe which traps water and thus prevents the free passage of air. You can see the trap associated with sinks and lavatories -- they're usually right underneath the sink. Just past each trap there is a vent pipe that eventually leads up outside on the roof, which allows airflow to facilitate the drains draining while still leaving water in the trap -- think of trying to drain a Coke bottle by turning it upside down. It won't drain smoothly unless air can be introduced to replace the liquid that's draining out. (That's a lousy analogy, but it's all I've got right now.)

Now think about your HVAC system, which I assume is forced air. Normally, this is a "closed" system, in that all the cold air sucked into the return-air ductwork is replaced by warm air coming out of the warm-air registers. There's a huge fan in the furnace that moves all this air.

I suspect there's a leak in the return-air ductwork, somewhere outside of the living space -- in the attic, perhaps. In this situation, when the big fan starts moving air, it'll suck some air in through the leak, but it has to exhaust all that air into the living space, thus pressurizing the living space. If you've got a window open, it won't matter -- the excess air goes out the window and all is well. However, with the windows all closed, that pressure is relieved taking the path of least resistance, which will be a small drain -- e.g., your lavatory. It will push the water in the trap out of the trap, thus breaking the seal. With the seal broken, air from the DWV system can then find its way into the living space. This "air from the DWV system" is called "sewer gas", doesn't smell good, and can kill you in high-enough concentrations.

No problem if you're selling the house. Just disclose this "material defect" and let the next guy worry about it . Seriously, any good HVAC contractor should be able to test the system and repair any leaks. Explain what's happening, and if he understands, he should be OK. If he says I'm full of it and there's no way this could be caused by the HVAC, get another opinion. There may be several people on this forum who can and may offer better advice as well.

Good luck.

Later addition: Some HVAC systems purposely introduce outside air to keep the inside air fresh. I have no idea how they avoid pressurizing the interior space with these systems, but in today's tight houses they'd better have a way. That good HVAC contractor I alluded to may have an answer.

 

[Gencon]

A typical HVAC system runs at about .5"WC static pressure. Not enough to affect the water in a drain. Especially if there are bathroom exhaust fans, chimneys,kitchen hoods or naturally vented gas appliances. Any pressure would surley be relieved by these long before a P-trap would be affected.

A few questions need to be asked before prollins' problem can be solved properly.
What type of HVAC system do you have?
Does the popping noise happen only with heat or when the fan is running by itself too?
Do all the drains in the house drain properly?
If you are draining the sink and you flush the toilet, is there any change in the sink?

A blocked vent pipe will result in the symptoms you have described.

 

[hj]

noise

Your airhandler's, (AH), drain is connected to the sink drain, (if you look under the sink you will see the pipe coming from the wall and connecting to it). In the summer time there is enough humidity to keep the AH's drain trap full of water so there is no air movement down the drain. Now that it is Fall, and almost winter the humidity is lower, and/or you probably have turned off the air conditioner so it is no longer creating condensation, so that trap has dried up. Now when the AH operates air blows down that pipe and you hear it in the sink drain. There is no cure because you don't want to keep adding water to the AH's drain every few days.

 

[prollins1]

HJ---Should I Just Let It Go?

The gurgling has stopped in the past few days but when the HVAC is running I can feel a slight breeze coming from the sink drain and also a slightly mildewy odor also.
Should I run the AC once to clear things up? It's getting up to 80 here in Houston tomorrow?

Thanks for the help....Happy Thanksgiving!

 

[hj]

breeze

The only way to stop it is to get water into the AH's condensate trap, and the way most are installed it could not be done. An alternative, if you can get to the AH is to install an open vent after the trap, which should have been done anyway but probably wasn't, so the air has an alternate way to exit.