any AC guys here? Need some assistance.

i have 2 AC units. both are in the attic and the secondary drain lines are in the soffit (2 story house). one of the lines started to drip a lot the last few days. in years past i would put a little clorox a few times a year in the open drain line in the attic next to the units but apparently i forgot in the last year or so. i have a open pipe leading down to a p trap that then leads outside i suppose. when i look down in it at the p trap i see water in both at the bottom but i suppose i am suppose to. i poured clorox in both of them a few times but the outside line is still dripping alot.

i then realized that the main AC drain lines go to the sink in a bathroom below the attic so i checked the sink there and water does not build up in that sink when i turn it on so it doesn't look like there is a clog there.

where should i look next?

both pans under the units in the attic are clear of water.

thanks,

one other thing - i tried running a few thin drain cleaning wires down the open line in the attic but i can't get past the p trap.

The sink line probably is under the sink around the water trap. That is where it is in mine and probably where its blocked. Its not the drain for your sink that is probably clogged. Its the line that empties into that line.
If it gets clogged you can take the trap apart and use a wire to get the clog cleared. Be careful to put a pail under the pipe because it will come a flood. As much as half a gallon.


Then start using clorox again.

i turned the water on in that sink to see if the bowl held water and drained slowly but it didn't so i don't' think that is where the clog is. if it were clogged the sink would have held water and drained slowly

There are ways to do this your self with some compressed air, a coupling and PVC glue, but you need to cover the sink drains these run into so you do not get the joy of cleaning the "stuff" in the drainline from your sinks, walls, ceilings, etc.

The sink drain is clear. It clogs right where your AC drain pipe empties into the sink drain pipe. Its happened to me 15 years ago.
If you take the drain apart and if the clog is like mine it is right where the AC drain empties into the sink drain.
You won't find the problem till you pull the drain apart.

didn't think about that. thanks, i'll check that tonight.

got an electrical fish tape?

those work good.

a little drano premixed with water, pour in at attic p trap, add enough water to get it to the lower tie in, let sit overnight, pour a half gallon or so down it in the am.

One of the things I've tried also at work, is to take some heavy gauge weed eater line and run down the pan outlet hole to help unblock that line. It will at least punch a hole through the clog so it can drain and get some bleach in.

Just curious, do you have a pool? I don't necessarily recommend this, but take some tiny-small chips from the pool tabs and put in the pan where the water exits and that will keep it clear for a long while.

Lay a towel in the sink and use compressed air to blow it out from the attic. The condensation from the ac doesn't have chlorine in it and grows algae in the primary drain and clogs it up. That's why you need to pour bleach down it twice a year.

This is someone that has learned from experience. I too learned about this the 2nd day on the job over 15 yrs ago.

Yeah when you "blow" that stuff out all over everything you will instantly regret it!

Something else that could happen if you blow it out with too much pressure you could blow the PVC pipe apart at one the fittings if they aren't glued well!

When you pour the bleach in the line, I hope it's not getting back to the evaporator unit. That would be bad news as it would corrode that expensive hardware. The evaporators are aluminum, and the bleach fume isn't good for them or the integrated condensate pan. There ARE proper products made for that.

If the safety pans are dry (you say "free of water") then you need to determine where that soffit drip is coming from. Both "facts" can't be true. The dripping soffit drain can't be from the pan if the pan is dry! How about your water heater? Is it in the attic, and is that soffit drain for the safety pan under the water heater instead?

It is standard for evaporator pans to drain into a "Y" drain fitting under a sink. They get clogged because of the slow water flow so that algae and scum grows, blocking the path. I think the best way to blow them clear is with water. It's more dense than air, so it clears the pipe better. I fit a water hose with a "jet nozzle" that has an on/off valve on it. I get the hose in place before I turn on water - it weighs less that way. I wrap a rag around that fitting you can see into (by the evaporator) to seal the jet nozzle and give it a blast of water, just a few seconds at a time. Yes, some will go back into the evaporator, but it won't hurt if you go with short blasts to avoid a flood. This approach has never failed to quickly blow the line out for me. After that, I drop an algaecide tablet into that p-trap by the unit.

BTW, you might check other sinks upstairs. If there are two available, each unit will drain into the waste system for a different sink. That still doesn't explain dry safety pans, but a dripping soffit drain. I'm wondering if you have a leaking water heater.

That's why I use water - simpler and lower pressure.

Quit using bleach-based solutions! Go to the hardware store and buy some algaecide tablets made for this purpose.