I’m having a little trouble understanding this concept from the text:
6.3.3 Condensate Drain Connections
Condensate drains from air conditioner coils, condensing furnaces, and heat-recovery ventilators should not drain directly into a DWV pipe. An indirect drain using an air gap should be installed. In some locations, the direct connection of a condensate drain line into a stack is not permitted, even with a trap. The potential danger is that sewer gases may enter the house through the condensate drain line. It is not a cross-connection problem, but it is unsafe and unhealthy.
If the “potential danger is that sewer gases may enter the house through the condensate drain line”, wouldn’t that also happen through the air gap? I understand the function of the trap is to stop the sewer gases from entering the building, but I don’t understand why directly connecting condensate lines is prohibited.
Is the rule in place to stop shoddy installs?
Is it because the connection to the DWV wouldn’t be trapped? But then there is this line:
the direct connection of a condensate drain line into a stack is not permitted, even with a trap.
Your explanation makes sense! This was one of those times where I understood the parts and pieces of the system, but just couldn’t visualize their installation arrangement.
Any thoughts on why a direction connection with a trap would be prohibited?
Some air handlers cause a negative air pressure in the condensate drain line.
Also any trap in a direct or indirect drain will dry out when condensate is not produced because the a/c does not run in the winter. That is why some areas do not allow any connection to the sewer vent.
There is a “Wet Trap” device that can be installed to keep a trap full. But installing one is costly, will freeze at an unconditioned location, and negates the reason your dumping in the sewer in the first place. “Cheap and Lazy”.
Those risers are incorrect.
Done all the time, still doesn’t make it right.
The air handler either sucks or blows down the pipe. Either way, it’s wrong. This one blows because it is a gas furnace. The quantity of air blown out the drain must be made up by sucking unconditioned air into the house from elsewhere, like a water heater flue etc…
Good diagram. The air gap shown will perform the same function as a drain vent After liquid goes through the air gap will prevent the column of water on the downside of the ptrap from siphoning the water out of the p trap.
See pic from an inspection I did today. I understand why there is an air gap and p-trap, but is it ok to have such an open connection where the condensate lines meet the drain?
