Thread: Unusual Air and Noise from Bath Sink - AC primary drain

HVAC guru's

Here's the setup: Residential new construction

Problem: Detected ununsual 'poping' noise and air rushing from the bathroom sink drain. When I fill the sink with water, it's slow draining and air bubbles come out.

Scenario: The primary HVAC drain is tied directly to this drain under the sink, before the trap. There's no trap at the air handler in the attic. The builder says the trap at the sink is fine. However, most new construction I'll typically see a trap close to the air-handler in the attic. Client is complaining with the effect of the noise and air rushing from the drain.

Possible solution: By installing a trap at the air-handler in the attic, would that solve the problem? Or is there another trail I should go down?

Thanks in advanced for your help?

Regards,
Phil

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The primary drain line (as you described) needs to be trapped;

M304.8.2 SEAL. The condensate drain system shall provide a seal thatprevents ingestion of air or other gas, through the condensate drip pandrain and overflow connections, from all outside sources, including thecondensate disposal place.Source Standard Mechanical Code 1997

The primary drain line needs to have a vapor trap installed. The noise you are hearing is a ramped up version of a kid blowing into the straw of his drink. Stop the free flow of air and you will stop the noise and the bubbles.

Based on the static pressure of an HVAC system (without other problems), a simple drain line trap is enough to do that.

Phil,

Also, and without going into all the gory details here (someone will, I am sure, provide a link to the information), this was discussed at length recently and the code does not allow the a/c condensate drain to make that direct connection - it must go through an air gap connection (not an air break, not a direct connection, but an "air gap" connection - *where allowed*. Without looking it all back up, my recollection is that it *is not allowed* regardless (when someone searches for the other thread and links to, all the views and supporting documentation will be there).

I saw more than one case where the homeowner thought they were losing valuable AC through the primary condensate vent and covered it over to prevent cold air leakage.

I remember one job where the homeowner covered over the primary condensate vent, then applied a bunch of sealant and silver tape to the air gap where the PCV emptied into the drain line.

John,

I see those all the time. The builder installs them wrong and tells the homeowner that it is installed to pour bleach every 6 month in-order to clean out the trap and other nasties. In reality, the darn thing was installed before the trap and just wrong.

The thing to do *IS* go ahead and cap that one off (with a removable cap) and install a vent after the trap.

Originally Posted by Jerry Peck

Phil,

Also, and without going into all the gory details here (someone will, I am sure, provide a link to the information), this was discussed at length recently and the code does not allow the a/c condensate drain to make that direct connection - it must go through an air gap connection (not an air break, not a direct connection, but an "air gap" connection - *where allowed*. Without looking it all back up, my recollection is that it *is not allowed* regardless (when someone searches for the other thread and links to, all the views and supporting documentation will be there).

I do indeed remember that discussion Jerry and I believe it was one of the very few we have had over the years where you and I ultimately needed to "agreed to disagree".

In any event, having an HVAC drain line tapped in above the P trap of a lavatory sink is an everyday AHJ permitted reality for many of us out here in the wild.

Here’s the link back to that prior discussion for others by the way…

http://www.inspectionnews.net/home_i...iguration.html

Originally Posted by Phillip Stojanik

I do indeed remember that discussion Jerry and I believe it was one of the very few we have had over the years where you and I ultimately needed to "agreed to disagree".

Phillip,

First, thank you for finding and posting the link.

You agreed to disagree, I still state you are wrong.

The difference is that the code *DOES NOT ALLOW THAT CONNECTION* ... period ...

*I* *still* do not understand what you do not understand about "Plumbing fixtures that are used for domestic or culinary purposes shall not be used to receive the discharge of indirect waste piping."

The code does, however, allow two (count them, 1 ... 2) exceptions, and only 2 exception, both of which are stated in the following code sections (which is copied from the previous thread). Those two exceptions are (and these are *THE ONLY* two exceptions): 1) "kitchen sink", 2) "laundry tray". And each has only one allowable connection in their respective exception. You will note that "lavatory" or 'bathroom sink' is not listed in either of those two exceptions.

It is clear, it is concise, and it is VERY SPECIFIC.

From the IRC. (underlining is mine)
- P2706.3 Prohibited waste receptors.

Plumbing fixtures that are used for domestic or culinary purposes shall not be used to receive the discharge of indirect waste piping. (Jerry's note: This is what cannot be connected where, i.e., do not connect an indirect waste to a residential sink or lavatory .... except as noted below.)

- - Exceptions: (Jerry's note: This is what can be connected where.)

- - - 1. A kitchen sink trap is acceptable for use as a receptor for a dishwasher. (Jerry's note: That ain't from no dishwasher, it's from an a/c unit. Thus is does not meet this allowable connection. Thus is meets the "Prohibited" section as to what cannot be connected where, i.e., that is not allowed to be connected to the sink trap.)
- - - 2. A laundry tray is acceptable for use as a receptor for a clothes washing machine. (Jerry's note: While this does not apply here, this deserves to be remembered also. The only thing which is allowed to be drained into the laundry tray (think laundry sink) is the clothes washer.)

I am at a loss to grasp how an intelligent and knowledgeable person cannot grasp such simple, precise, concise, and specific wording. It's not like it says 'maybe' or 'if you want to' or 'or similar sink' in there anywhere.

Originally Posted by Jerry Peck

...I am at a loss to grasp how an intelligent and knowledgeable person cannot grasp such simple, precise, concise, and specific wording. It's not like it says 'maybe' or 'if you want to' or 'or similar sink' in there anywhere.

Jerry,

I do not dispute the code language or its intended meaning as you have previously presented it. My point of contention is with the local interpretation and application of the code where this particular topic is concerned.

I just can't argue with the fact that the drain line configuration in question is the commonly accepted way to make this connection in this part of the woods and I am not aware of any local AHJ that does not willingly permit it. Where code enforcement is concerned, your local reality and mine just happens to differ on this point.

I do fully realize that that does not make it right from the purist code interpretation point of view, but it does not change the local reality that local inspectors have to deal with here.

If we write this up as a problem we will get no support from any quarter; no backup from the licensed HVAC contractors who recognizes this as the preferred connection method, no back from the local licensed plumbing community who facilitate this connection within the scope of their work, no backup from the local code authority, and no backup from TREC when the complaint is filed against us by a ticked off seller.

Call us "back woods" if you will but can you at least appreciate our predicament?

Originally Posted by Phillip Stojanik

I do fully realize that that does not make it right from the purist code interpretation point of view, but it does not change the local reality that local inspectors have to deal with here.

If we write this up as a problem we will get no support from any quarter;

Call us "back woods" if you will but can you at least appreciate our predicament?

Phillip,

I don't call you "back woods", and I do understand an appreciate your predicament, HOWEVER ...

Down in South Florida we (home inspector who cared) suffered through the same lack of back up from anyone, BUT, we kept writing it up, providing the code sections, kept discussing these issues (there were many like this) with the local building officials, and, *eventually* the local building official (I guess) got tired of hearing from home inspectors about what the code said and why weren't they (code inspectors) applying the code, and, eventually, those same code inspectors began enforcing those items.

It did not happen overnight, it took many years, but, because the code was so clear and concise as to what it was saying, perhaps those code inspector re-thought their positions and started enforcing the code. How many years? Be patient, maybe 10 years or more - but persistence pays off.

In the mean time, you just have to 'suck it up' and write it up, with the back up code section, and when you get no support from anyone, your client will read the code section you provided with in your report with the write up and think 'Jeez, is my home inspector the only one who can read? this is so clear in not allowing that.', your client will know you are right, and, eventually, so will others.

Just because 'everyone' exceeds the speed limit does not change the fact that the speed limit is what it is - and is clearly stated what it is.

I am curious as to how detrimental a connection like this could be. I see them all the time. They start at the evaporator coil, properly trap the drain line there, run the drain pipe downhill to a tailpiece under a bathroom sink and connect it before (on the sink side not sewer side of) the trap. I see it installed this way on every single new home an many older homes in my area.

What would the worst case scenario be for this type of indirect waste connection if it is properly trapped and configured. I do not buy into the bacteria from the evap coil condensation either, algae maybe, but I am sure there is already plenty of bacteria floating in my bathroom sink p-trap from brushing my teeth, washing hands, etc that would be far more dangerous than bacteria growing in the water of the condensation drain.

I ask this because I inspect in several jurisdictions who use diferent editions of the code, and they all allow this type of connection, regardless of what the code states (and yes, I have contacted the BO reps directly to ask them if it is accepted). On some houses that are ten years old or more I have seen this type of connection and after ten years could not detect a problem with the configuration.

If it is a real problem to do it this way, why is it allowed by so many jurisdictions, and obviously, not just in my part of the woods?

Just curious.

Originally Posted by Eric Shuman

I am curious as to how detrimental a connection like this could be.

If it is a real problem to do it this way, why is it allowed by so many jurisdictions, and obviously, not just in my part of the woods?

This was discussed on the other thread which Phillip posted the link to. No need to re-hash all that information.

Hello all,
I'm not an inspector, but an annoyed homeowner whom since having the primary drain line blown out due to overflow into the drain pan, is experiencing this same gurgling, popping noise. The worst part it is the sink is 20 feet from my bed and it is loud and waking me up at night.

After reading this thread I went to my attic and traced the line from the AC to the point where it drops into the floor where I can't see it anymore. There is no trap (at least one that looks like a normal P-trap) between the AC unit and the floor, nor is there one near the sink where it intersects the pipe on the sink side. Could I install a trap just before it intersects the pipe for the sink or would I be causing more issues? I would like to find someone in the Sugar Land (suburb of Houston) area who could do this for me if you could refer anyone.

Finally, I see that this is an "Inspectors" site, so if I'm intruding as a consumer, I apologize, and someone please tell me to buzz off! If not, I would greatly appreciate any help you can provide!

Thanks!
Nick

Nick, when you have your unit serviced this year, you should consider having them install the trap at that time. That way the cost will be much less than having them make a special trip just for the trap. Stay away from anyone offering $39.00 annual service. They will try to upsell you on something else. I know I wouldnt fire up my truck and drive to a clients house for $39.00.


And yes. You should have your unit serviced at least annually. It does make a difference. You can check the BBB in Sugar Land or Houston for an HVAC vendor. I dont personally recommend individual companies (conflict of interest).

Best of luck

Nick,

Questions from non-inspectors are always welcome. No buzzing-off necessary.

You might check the link that Phillip posted. While the original question and pics have been deleted for some unknown reason, the answers are still there and Richard Rushing posted a diagram. If I am correct in my interpretation, JP's code reference requires an "air-gap" or separation between the coil box and the sink drain connection. I would guess that the best place for that would be in the vertical section of pipe after the p-trap (using R.R.s diagram). That should also prevent air from being forced down the pipe and into the sink drain.

Thanks John and Gunnar! I appreciate your quick responses!

Originally Posted by Gunnar Alquist

If I am correct in my interpretation, JP's code reference requires an "air-gap" or separation between the coil box and the sink drain connection.

Gunnar,

The correct interpretation of that code is ...

... that the a/c condensate *IS NOT ALLOWED* to be connected to the sink drain ...

... regardless of how it is *NOT* connected.

Here are a couple of diagrams that might be helpful.

Jim,

That first photo is showing exactly *WHAT IS NOT ALLOWED* if that sink is used for domestic use or for culinary use.

The second drawing does not show, or even indicate, the required trap on the secondary condensate drain connection.

Jerry, your right.

But, I was not trying to reinvent the wheel for a consumer who obviously has a system installed similar to the diagram that I stole from someone who posted it here from "Code Check" and there was not secondary drain question. Nick Vellani needed an answer about a gurgling sink drain.

Hello Friends!

We had such a problem with noise in the primary condensate drain line. It was a noise new to us since I flushed out the drain lines from both attic air handlers, one of which had become clogged. It definitely sounded like water dripping very slowly, which was a little surprising as with the recent cold snap we've just begun using the heater side.

The line drains from the attic to a first-floor lavatory tailpiece, so is separated from the sanitary line by the trap at that lavatory sink. There is a loosely-capped vent at the air handler, but no trap there.

Here's what has seemed to work for us: Urged back to this drain line task by that annoying drip, I finally opened the trap and tailpiece down at the lavatory sink. I found that lots of gritty, wet debris had accumulated in the tailpiece and in the hose from the upstairs drain. Water could find its way through all that mess, but apparently not very well. I cleaned it out really well and sucked what else I could out of that hose with a little wet-dry vac. I was surprised how much junk came out of there and realized, of course, that I should have done this cleaning earlier.

I think all that debris was still wet from the cooling season and the airflow from the furnace was now nudging the water through it, one annoying drop at a time. It probably would have dried up and quieted down on its own, but then that mess of debris would have caused more trouble later. The noise is gone and now I know the drain is clean, top and bottom. Regarding "thorough," I only regret it when I'm not.

Thanks!

Glad you got the noise to stop but a proper trap at the unit discharge will stop air flow through the drain pipe (not supposed to flow air, only water.)
Of course periodic cleaning is always a good thing.

Originally Posted by Jim Luttrall

Glad you got the noise to stop but a proper trap at the unit discharge will stop air flow through the drain pipe (not supposed to flow air, only water.)
Of course periodic cleaning is always a good thing.

Thanks for that, Jim. I'll correct as needed and as you recommend.

The existing installation is how the house was built, about seven years ago, I think. (It wasn't a great drain installation as the secondary drain pan was installed in such a way that any condensate would overflow the tray before it could reach the secondary drain pipe--the pipe connected at the tray sloped up to reach the drain line. Also, the installer insulated the secondary drain line and not the primary.) No trap was installed at the air handler but there was an uncapped open-air "vent" in the primary drain line. (I've read suggestions that putting a removeable cap on that "vent" would reduce air loss and also allow flushing of the line.) As mentioned above, the drain line runs down to the tailpiece at the lavatory sink, where it is protected from the sanitary drain line by that lavatory trap.

So, an inline trap at the air handler would be in order. And, the vent for that trap would be after the trap, and that vent should be left open. This will limit air flow but not water flow. I suppose we would have to make sure that trap doesn't dry up during the non-cooling months.

Would that be about it?

I was wondering why, when the house was being built, the AC folks would install the system without the trap.

Thanks very much!

Originally Posted by steve patrick

Thanks for that, Jim. I'll correct as needed and as you recommend.

The existing installation is how the house was built, about seven years ago, I think. (It wasn't a great drain installation as the secondary drain pan was installed in such a way that any condensate would overflow the tray before it could reach the secondary drain pipe--the pipe connected at the tray sloped up to reach the drain line. Also, the installer insulated the secondary drain line and not the primary.) No trap was installed at the air handler but there was an uncapped open-air "vent" in the primary drain line. (I've read suggestions that putting a removeable cap on that "vent" would reduce air loss and also allow flushing of the line.) As mentioned above, the drain line runs down to the tailpiece at the lavatory sink, where it is protected from the sanitary drain line by that lavatory trap.

So, an inline trap at the air handler would be in order. And, the vent for that trap would be after the trap, and that vent should be left open. This will limit air flow but not water flow. I suppose we would have to make sure that trap doesn't dry up during the non-cooling months.

Would that be about it?

I was wondering why, when the house was being built, the AC folks would install the system without the trap.

Thanks very much!

Yep, you seem to have the concept in hand.
As to why installers don't put in correct traps, they were not taught properly and no one forced them to read the installation instructions!
If the trap is the correct depth, you likely won't have enough evaporation between seasons to worry about but a bit of mineral oil will help prevent trap seal evaporation and not impede drain function.

Primary and secondary drain ports both require traps unless a switch is installed instead of a drain at the secondary drain port.

Originally Posted by Jim Luttrall

Yep, you seem to have the concept in hand.
As to why installers don't put in correct traps, they were not taught properly and no one forced them to read the installation instructions!
If the trap is the correct depth, you likely won't have enough evaporation between seasons to worry about but a bit of mineral oil will help prevent trap seal evaporation and not impede drain function.

Primary and secondary drain ports both require traps unless a switch is installed instead of a drain at the secondary drain port.

Thanks for all that! What sort of trap would you recommend for these lines?

Originally Posted by steve patrick

Thanks for all that! What sort of trap would you recommend for these lines?

Check the manufactures installation manual. They usually will have dimensions and diagram. Just use standard PVC fittings and pipe to construct one.
The following may not be 100% correct but give you the idea. The first diagram that I got from Carrier does not show a vent at the downstream side of the trap and is technically a "running" trap.
The second photo shows a correct trap with vent and a water sensor switch in the secondary drain port in an up flow unit.
There are prefabricated traps with clear pipe at the trap that are available on the internet and maybe some stores.