AC Drain Pipe Vent Trap Going Dry - Sewage Smell - Plumbing - DIY Home Improvement | DIYChatroom


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Plumbing

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 04-26-2011, 09:53 AM   #1
Member
 
Join Date: Apr 2010
Posts: 350
Rewards Points: 258
Default

AC drain pipe vent trap going dry - sewage smell


Hey all,

I'm nearly done my basement remodel. Original construction had the HWH near the big main house drain pipe. Tapped into that was a set of smaller pipes. They make a single exit from the main drain. Then it sprouts upward 3 feet to a Studor vent. Off the bottom of that is a trap, which leads to an open top pipe also 3 feet tall standing next to the Studor vent pipe. The only apparent purpose to this open pipe was that the HWH had a copper pipe running out of it and into this pipe - presumably emergency HWH overflow.

In the past, on rare occasions, I'd notice the faintest sewer smell. We also once had a fly bloom down there - not the little triangle dumb/slow looking fruit fly types - but your classic "fly". Never happened again. Could have been unrelated.

We had some HVAC work done and the HWH moved. Now, the HVAC guy has run a PVC drain for AC overflow to this existing same open-top pipe that leads to the main drain. The HWH continues to have its overflow running there too.

I realzed that previously, the HWH probably never overflowed - so the trap in that drain was likely bone dry - probably where the smell came from as this is on the main house drain.

Now with HVAC AC drain running into it - that will keep the trap wet in summer months when AC is running.

But not in the winter. I pointed this out to the plumber. He showed me this little flip-valve on the HWH overflow. Open it briefly, and it drains hot water into that drain - to wet the trap. He just said to do it on occasion.

This just simply doesn't seem right. So I'm trying to think premptively - could I simply tightly enclose the open top of this HVAC/HWH drain in question with spray foam or even plumbers tape or silicone? Then - who care is the trap goes try in the winter. Maybe sealing it would keep it more moist in there anyway.

My main concern is that before, this was all out in a big open room. But now, it's in a one-foot wide space behind a wall that's open to my new HVAC/HWH area. I don't want those units sucking sewer gas out of this drain and spreading it through my house...

Thoughts?

Advertisement

denemante is offline   Reply With Quote
Old 04-26-2011, 12:46 PM   #2
Member
 
Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 6,976
Rewards Points: 2,048
Default

AC drain pipe vent trap going dry - sewage smell


Don't trip the water heater overflow (pressure & temperature relief valve) too often, twice a year is enough. If you need water to fill the trap, bring it downstairs in a pitcher or watering can.

Heating and air conditioning units should suck air for climate control via a return air vent coming down from the house, not relying on basement air unless there are heat or cool air registers with more square inches in the basement. HVAC equipment partitioned off and needing intake air must have louvers to the outside or louvers to the rest of the basement. Combustion air should come from a louver or intake pipe to the outside.

Advertisement

__________________
Forget super sized fries. The Washington Redskins could promote healthy eating with First Lady Obama by choosing a (red skinned) turnip for a mascot.

Last edited by AllanJ; 04-26-2011 at 12:49 PM.
AllanJ is offline   Reply With Quote
Old 04-26-2011, 01:39 PM   #3
Member
 
Join Date: Jul 2008
Location: Canada (s/w ON.)
Posts: 2,294
Rewards Points: 1,000
Default

AC drain pipe vent trap going dry - sewage smell


I have a/c and a forced air furnace. There is small pump beside the furnace that pumps the a/c condensate through a 3/8" plastic tube to a drain in the same manner as yours.
The furnace has a humidifier attached and it also has an over-flow connected to the condensate pump.
In the winter the humidifier over-flow maintains the drain trap and the a/c does the job in the summer.
Wildie is offline   Reply With Quote
Old 04-26-2011, 02:17 PM   #4
Member
 
Join Date: Apr 2010
Posts: 350
Rewards Points: 258
Default

AC drain pipe vent trap going dry - sewage smell


Once drywall is up - I'll have no way to reach this pipe to manually pour water into it. The only source would be AC overflow and the HWH. The plumber didn't say I should only use that release valve only about twice per year - he said I should do it anytime I think the trap is dry. Is that ill-advised?

My only other choice is to run my own PVC to that drain pipe in question so I can access it from a few feet away.
denemante is offline   Reply With Quote
Old 04-26-2011, 02:20 PM   #5
Member
 
Join Date: Apr 2010
Posts: 350
Rewards Points: 258
Default

AC drain pipe vent trap going dry - sewage smell


one other thing - you mentioned HVAC gets air from the returns - is that 100% true, or does some air for conditioned air enter directly into the unit then become circulated in the house? The returns are in a completely different room. The HVAC and HWH would still presumably have some kind of suction since they are gas and burning air. But in those cases - I wonder if that's enough suction to "suck" sewer air from 9 feet away out a 3 square inch gap in the top of the drain in question. Even if it did - I suppose it would be burned and sent out my exhaust. There will be ample combustion air in the room.

Thanks,
Dan
denemante is offline   Reply With Quote
Old 04-26-2011, 03:18 PM   #6
Plumber/Contractor
 
TheEplumber's Avatar
 
Join Date: Jul 2010
Location: North Idaho
Posts: 7,251
Rewards Points: 2,620
Default

AC drain pipe vent trap going dry - sewage smell


Google trap primer. Put one on the drain. This will solve your dry trap problem. Don't seal the pipe closed. You won't have gas issues with the primer installed
__________________
When posting in forums, letting us know your location will help others give better feedback/advice/solutions to your questions
TheEplumber is online now   Reply With Quote
Old 04-26-2011, 07:52 PM   #7
Member
 
Join Date: Jul 2008
Location: Canada (s/w ON.)
Posts: 2,294
Rewards Points: 1,000
Default

AC drain pipe vent trap going dry - sewage smell


Quote:
Originally Posted by denemante View Post
Once drywall is up - I'll have no way to reach this pipe to manually pour water into it. The only source would be AC overflow and the HWH. The plumber didn't say I should only use that release valve only about twice per year - he said I should do it anytime I think the trap is dry. Is that ill-advised?

My only other choice is to run my own PVC to that drain pipe in question so I can access it from a few feet away.
I think that it would be a mistake to bury the drain behind the drywall. There will be times when maintenance will be required and having it hidden away is asking for trouble.
Hinged panel doors are available to allow maintenance on utilities.

Advertisement

Wildie is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Frozen Vent Pipe Ratchye Plumbing 40 12-27-2013 01:00 PM
Venting ponch37300 Plumbing 41 02-23-2013 11:37 PM
Leaking drain pipe under kitchen sink dethun Plumbing 20 09-26-2012 08:30 AM
drain pipe from HVAC in attic dripping on to sheetrock gnostic19 HVAC 7 03-22-2011 04:05 PM
Vent directly between trap and drain, or not? wvphysics Plumbing 17 07-18-2010 05:37 PM




Top of Page | View New Posts