I'm doing a little pre-season maintenance on my AC units..., cleaned the outside condenser fins/tubes and gave the evaporator coils in the attic a look over, they are clean. I put pan tablets in the evaporator trays to hopefully help keep the condensate drain lines flowing. Last few Summers it's been a challenge to keep those condensate drains from clogging up. Do any of you HVAC guys have any tips on how to keep those drain lines from getting stopped up (besides the pan tablets and a little bleach) or tips for any other preventative maintenance to do?

I had that problem with my first unit, but never did a thing to my replacement unit. Never had a problem.

Mine actually ruined about 4500$ of wood flooring about 4 years ago, made some sweet deer blinds tho. Best practice I've found is remove all the water you can from the pipe and pour about a cup of bleach in it, I use my coffee maker just to fill the the pot with hot water and pour the hot water into the pipe. I do this every other month, I have it set up on my calendar in my Iphone to remind me.

same happened to me. I had them install a water sensor on the new one so it will shut off before overflowing and ruining my floors again.

Where does your condensation line drain?

Outside, into a sewer trap on the floor, under a bathroom sink drain or into the tub waste and overflow?

That snout is hard to kill. You have to treated aggressively enough to kill it. But you need to flush the dead debris. You may have piping issues or termination issues...something holding unwanted condensate.

RedRanger has asked a good question. You guys discuss. I will follow along.

Primary drains for both units go to bathroom sink tailpieces, secondary/overflow lines dump outside at the soffit areas, neither unit has an emergency/overflow shutoff switch - only the large secondary catch pan under the units with the lines leading to soffit areas. The primary lines each have 4-5 right angle bends between the initial p-trap and the point where they dump into the sink drains. The only cleanout point I have is the vent/riser just after the initial p-trap, so far I have not been able to snake anything past all those 90 degree bends.

Several years ago I installed clean outs in the PVC piping (before the trap) that drains the primary pans. They're nothing more that T-sections with about a 1 ft section of vertical pipe and end cap, which is not glued so that it can be removed. In the Spring I remove the cap and pour a little bleach in them, then flush with water.

I'm gonna replace my traps and add a capped cleanout before the trap (like Dan did) and maybe get rid of a few 90 degree bends. The lines are hard-plumbed to the sink drains, there's two 90 degree bends under the sink that I might see if I can replace somehow with a clamped flex line that I can remove for cleaning.

This is how both units are setup in the attic areas, I'm betting most of my problems are at the initial attic p-trap or the cluster of tight bends under the sinks.

i heard vinegar is what your suppose to pour down those drains

Looks like you already have a clean out just after the trap.

At area 1...that is a vent, not really a clean out but can be used to clear line. Also, the trap is not level.

At area 2.. this area is holding water. The trap needs to leveled, replace the 90 degree ell with 2 45 degree ells. This will give you a sweep rather than a 90.

Area 3. .this line has no down grade. Leveling trap and intalling 45 degree ells will alow you obtain grade toward verticle drop in wall. Also, look down the horizontal run, remove any bellys or sags.

You might post a pic under sink.

I would replace this ell with a tee. You can add drain treatment at the trap entry. It will need a standpipe and be plugged or capped. The vent goes after the trap. Stand pipes must terminate at a height above the over flow.

If your not comfortable, get some professional help.

I had that flatten trap on both my A/C units, That is the only place it has clogged up on me. I replaced the trap with a real trap and so far no more issues.

I pour bleach down the unit every year before the A/C starts working a lot.

Yep to all that above....., area 1 vent only allows me to add a little bleach there but it doesn't treat the trap and I can't clean the trap from there. Definitely adding a tee on the other side of trap thaf I can cap after cleaning the trap (and I'll level the new trap). Area 2 is a spot for sure where I'll do away with the 90. The pic is a little deceiving, there's good downslope from 2 toward 3 and no belly sagging in the horizontal run before dropping down the interior wall to the bathroom. This was a new house build 12 years ago, cutting and glueing together pvc pieces is easy. I will do a much better job fixing this setup.

Let me post a pic under the sink.

Here's a pic of the drain tie-in at the bathroom sink tailpiece. There's a pair of 90's right there and another right inside the wall. I think that point where it attaches to the tailpiece is trouble, no way to clean it out without tearing apart the sink drain. Would like to replace the pair of 90's with something I can easily disconnect from the sink tailpiece for cleaning. There's about a 4" straight stub between the first 90 and the wall.

This could be where you bigest problem is. Seen this more than once.


If the sink tailpiece extends past the 3/4 inlet of the tee, you can have sink semi solid waste build up between the chrome tailpiece and the inside of the brass tee.

To check...remove the trap. Put you finger up insde the brass tee. If you cant feel a 3/4 inch opening where the pvc connects to brass tee, then the tailpiece is too long.

I dont think the ells under the sink are of concern.

Last time I had a clog, took the trap off and I was able to feel the opening, tailpiece end didn't extend down that far. I could feel the opening but it was plugged solid with black crud. I couldn't get a cleaning brush or anything to it to easily to clear it, ended up bending the tip of a heavy zip-tie to clear it. Gotta be a better way for that area.

That set up is common and troublesome. I found a DYI device at Harbor Freight. It is like a bottle brush on a 30 inch flexible handle. It helps some.

Sounds like you got it going as good as anyone. Wished I had asilver bullet for you.

shop-vac on the line works wonders (violently sucks all that snot out . . .)