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Hi Robert,
I noticed that one of the corners of my bathroom rug (next to the bathtub) was wet, and I thought that the tub was leaking. I then saw water was not only on the baseboards but also on the wall. My husband said a pipe was leaking and started sawing through the wall. After almost all the wall was removed, we discovered that there is a pipe leaking but it’s coming from the air conditioner in the attic. My question is why there are two drain pipes there, and why was there a P-trap on the pipe that was leaking? I called the A/C people and they said to keep gasses from going into my attic. We replaced the broken pipe with a straight piece, without the P-trap. Is it necessary for the trap to be there?

Thank you,
Helen S.

Hi Helen,
Well, the only time you put a trap in is if you’re tied to a sewer line which would prevent gasses from escaping. If you’re not sure, I would give the installers the benefit of the doubt and think that the trap is there for a reason, and would put the trap back.
The two lines you referred to are the primary and secondary. One goes to the outside and the other to the inside. The primary sits in the lower corner of the pan. These pans are slightly pitched which forces the water to the primary. By code, these lines go to a lav. This would be the closest sink whether a laundry room or bathroom. This line is tied in and basically recycled. With some buildings, the A/C condensation is running off onto a roof. With sun and water exposure, this will eventually rot the drip edge and will damage the roof.
The secondary line is there for an overflow in case the primary is clogged and discharges out to the outside of the building.
While we’re on the subject of air conditioners, let me mention again how important it is to keep the filters clean. Some people like to keep their doors open. This lets in more dust than average which collects on the A/C filters so they have to be changed out more often.
If you don’t keep the filters clean, it will cause the A/C unit to condensate and will cause problems. This dust will travel to the A coil, which causes the exchange from hot to cold, and is very difficult to clean. You have to take the shrouds apart which do get costly if you have it done. Not only that but excess dust translates to the unit not running efficiently, meaning it takes much longer for your house to cool giving you a much higher bill – not to mention the additional wear and tear.
Keeping your filters clean will save you a lot of money and headaches in the future.

Submit your questions to: robert@imsconstruction.com. Robert Lamoureux of IMS Construction, Valencia, CA, has 25 years experience as a commercial General, Electrical and Plumbing contractor. The opinions expressed in “Ask the Expert” are not to replace the recommendations made by a qualified contractor after a thorough visual inspection has been made.

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