I'm very confident the source of this problem is the condensate drain being tied into the same drain as my septic system. In the photo you can see the central air mover with the drain angled down towards a p-trap drain. I do not know exactly where the drain leads to but periodically we get the smell of sewer gas in our house and it appears to be located mainly in the hall area where the unit sits. Does anyone have any idea if this is supposed to be piped this way and if not do you have a fix? HELP!
Septic gas in AC drain
- Thread starter troy64
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JWII
New Member
It doesn't matter if your A/C is connected to your sewer or not because most of the time it is. As long as the drain it's connected to is properly vented you'll have no problem with sewer gas. Sounds like there is a venting problem and if it's not vented right the water in your A/C drain p-trap is getting sucked dry when a toilets gets flushed or tub drained. If that's the case you can add a vent before the p-trap but it needs to extent through the roof or revent into and existing vent.
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JWII
New Member
JWII
New Member
Also if the drain connected to your A/C drain is vented properly you could remove the cap form the A/C drainline and smell no sewer gas. Really the caped pipe should be uncapped and extended up a couple feet just to vent your drainline. Anything that drains draws air.
MACPLUMB
In the Trades
Also that floor drain in front try pouring a quart of water down it I don't think it has a trap primer,
and would be a source of gas smell coming up
and would be a source of gas smell coming up
Bluebinky
Member
There appears to be a trap on the far right. There does not seem to be anything to keep the trap full when the AC is not being used. That could be the problem if the drain is to the sewer. If not to the sewer, it would at a minimum be a small air leak to the end of the drain (not unusual, though).
This shows a trap with trap primer for the AC drain.
Every so often, the primer drops some water in to keep the trap full, preventing sewer gas from entering the home.
Bluebinky
Member
What type of trap primer is that and does it really still work?
Put another way, does anyone know of a reliable trap primer that does not require a pressure drop nor cross flow, and costs a reasonable amount (less than say $200)?
Put another way, does anyone know of a reliable trap primer that does not require a pressure drop nor cross flow, and costs a reasonable amount (less than say $200)?
Looking from the air unit left just past the capped nipple there is back to back 90's. From there the small pvc drain line changes to a 2" P trap which runs back or in a north direction. Based on the layout of the house my best guess is that this ac drain is tied to a tub drain which is located on the same north side as the direction of the 2" pipe. This area is a master bathroom and it's very likely the drain line is tied to the sewer vent for the bathroom. As JWII stated it is probably tied into a line that when drained or flushed is causing a siphon. It's not a daily or even weekly problem but definitely one that pops up several times a year. Without tearing out sheetrock to locate all the piping I'm not sure if there is a fix based on the current setup ie another vent, etc.
Themp
Active Member
I am surprised that the air handler does not have a backup drain, so if the main gets blocked then it will dump into the backup. Usually the backup is just a pan that sits under the air handler that is drained some where. Right now if the main gets block, which it can over time with mold and such, the condensate is going into the hallway area.
A trap primer plumbed with the option of priming several things at once. Normally you leave off the spreader and just prime one trap.
Bluebinky
Member
Like many others, that primer requires at least a 10 psi drop to operate. Nowhere in any of my houses does the pressure drop nearly that much. My guess is that OP would have the same problem. The only other options seem to be $500-ish commercial electronic systems or the flow-through primers. Anyone have ideas for a reliable and cheap primer that does not need to be near (and gravity feeding below) a fixture?
A trap primer plumbed with the option of priming several things at once. Normally you leave off the spreader and just prime one trap.
I was able to use a small scope camera to look in the p trap on the upstream side of course. Plenty of water. I drained tubs, flushed toilets and the water level remained the same. Now I am back at square one. A few days ago we used our washing machine pretty extensively and later that day noticed the smell of septic gas AGAIN in the space where the air handler is located. This area of the air handler is open up top and you can see the bottom of the upstairs floor as well as the various ac ducts that are routed throughout the 1st floor. Does the washing machine have a connection to this vent system or does it go straight to the septic tank due to enough force by the washing machine? If it's not connected then I am starting to think there is an opening in one of the septic vent pipes between the floor space and it's finding it's way to the air handler area. For clarification are just the toilets connected to the septic vent pipes?
