Air Conditioner Hack

24 Jul

Here’s a non-computer design related entry. My friend Wayne inspired me to fix my air conditioner drain issue. Mine’s been leaking condensation into the overflow pan all summer. The overflow pan is doing its job, carrying the water away outside the house through a PVC line out to the eave. But rust is building in the pan, and the fact that water was dripping out meant it was flowing somewhere that it wasn’t designed to, and that is never a good thing.

The end result, an easier to maintain drainWhy was it leaking where it shouldn’t thus dripping into the overflow pan? Because the main line (a closed line from the air handler to the sewer line) must have been blocked. Given the system is over 35 years old, there’s no telling what gunk had built up in there over that time. But because the line goes right into the air handler without any connectors, I couldn’t find a non-destructive access to flush or snake the pipe. A bad design (a closed system) kept me from maintaining favorable conditions for maximum throughput.

Armed with various elbows, t’s, and connectors to fit my 3/4″ pipes, PVC primer and cement, a Dremel (I’m always looking for something to Dremel), and a brand new and wonderfully designed shop vac , I headed up into the attic.

The project took much longer than it should have for several bone-headed reasons I won’t go into now. But by the end, I had cut open the line and used the shop vac (and a few drain-cleaning chemicals) to get water flowing easily through the line again. When I put it all back together, I replaced the first elbow joint with a T and a cap so that every few months I can easily pour some bleach down the pipe to keep it clean.

The AC ran intermittently through the night (it might just be psychosomatic, but it felt like it ran cooler). In the morning, the overflow pan was completely dry. There’s still lots of rust in there, but cleaning that is a project for another day. Checking the pan again this evening, a full day of operation after the clean-out, it is still dry. I can assume that water is flowing out in the route it was originally designed, and holding up well during the year’s most active use.

So, why didn’t they install the pipe with an easy way to maintain it in the first place? Could have been time or cost constraints. Or, it could simply be that design often takes several iterations before an ideal solution is produced.


Posted by on July 24, 2006 in fribble



26 Responses to Air Conditioner Hack

  1. wayne

    July 25, 2006 at 9:32 pm

    There is a sealant spray that you can use to coat the bottom of the pan after you clean out debris. I can’t remember what is was exactly, but it looked like something you can get at Home Depot.

  2. Mark

    July 26, 2006 at 6:46 am

    I’ll look for it. I did see a solvent to help get rid of the rust. That’s the “next action” on my “maintain A/C” project. : )

  3. Luis Garcia

    August 29, 2006 at 12:38 pm

    An easy way to clear the overflow pvc pipe is to acquire a cheap sprayer at your local hardware store ($15). With this sprayer you pump it tightly with air only and then release tha air into the pipe. Repeat this process multiple times into the pipe and you are golden! I learned this from my A/C man who promptly charge me $75 for his service call.

  4. Merle

    September 4, 2006 at 7:24 am

    Where can I buy a new ac water pan – 28″ x 50″
    Thank you.

  5. Mark

    September 4, 2006 at 7:32 am

    Hmmm …. good question, Merle. My A/C repair guy made ours custom from thin gauge sheet metal. I suppose Home Depot or Lowe’s might carry some stock sizes? I don’t know if 28×50 is a standard size or not.

    If you’re handy with tin-snips, it should take too much effort to make one for yourself. from a 32×54 sheet.

  6. Tony F

    March 2, 2007 at 1:54 pm

    I have a similar issue and just blastedted my main-line clean-out (at least mine had a pre-built clean-out) with air. I’m curious what chemical you cleaned the main drain line with (1 cup of bleach?) and if you got the drip-pan de-rusted? I’m thinking of using CLR clearner on the drip-pan assuming I can remove it (got lots of rust). Could go for the new drip-pan approach if things get crazy, but would probably have to out$source that due to my lack of skilz.

  7. Larry Gonzalez

    June 2, 2007 at 7:18 pm

    Dude, your idea was the best. Used the air compresor instead of pump sprayer. Also, since I capped my washouts with threaded couplers, I screw in a cap with a hole drilled just big enough to insert the air nozzle. A couple of bursts like you said and I could hear the water runnning through the drain which exits into the house plumming. The “shower” outside stpooed and the hole the leak made is drying out. Thanks again for the tip.

  8. dan

    July 10, 2007 at 4:08 pm

    My air conditioner is leaking into the overflow pan underneith. The pan is doing its job and sending the water out of the house through pvc pipes. But why is is leaking in the first place the house is only four years old>

  9. Mark

    July 11, 2007 at 8:21 pm

    The main drain line must be clogged, Dan. The post above describes how to clear that line if it does not already have a convenient means to do so already.

    If you can find a way to pour bleach and water mixture into the line, that might be enough to clear it out. If not, you’ll likely need to flush it with something more forceful like a blower or power washer.

    Good luck!

  10. cile

    July 29, 2007 at 1:57 pm

    Okay. That’s all great information. I was aware of the bleach tip and have used it many times. However, today I mistakenly grabbed the gallon vinegar container instead. So, now what do I do, since vinegar and bleach mixture can be toxic. AC’s are all stopped up and the house smells like an Easter egg boiling and coloring party.

  11. Sarah

    August 4, 2007 at 2:02 am

    My husband is currently trying to fix are clogged A/C pipes, but for the smell of vineger you can use some lemon juice and baking soda to help clear out the smell quicker. You can use baking soda for just about anything, it might even take out the rust stain that one of you was talking about. Good Luck to all

  12. Mark

    August 4, 2007 at 7:48 am

    Thanks, Sarah. I have to replace our filters this weekend. I might just give that a try. I’ll let you know how it goes.

  13. Jay

    August 5, 2007 at 3:37 pm

    I had a simular problem, but unfortunately the genius who installed my ac used too short of a overflow pan. The system worked the way it should, but the overflow drip was outside the coverage of the pan. I got a very “reasonable” quote to clean out my condensation drip line. Here in Phoenix hvac service companies only charge around $300.00 to do the ten minute job. I opted to go to HomeDepot and buy about two dollars worth of pvc fittings instead. I used a water hose connection instead of air. I was a little concerned about running a garden hose into my attic, but it did a fantastic job. After turning the hose on and off a few times I drained the hose, cut off the hose fitting and reattached the drip line using a 3/4″ pvc fitting. now all I have to do is decide wheather to pay a hvac tech $1,000.00 to put in a properly sized pan or buy a prefab one for about $125.00 and do it myself. Hmmm I wonder, well I probably have a spare hour to save $875.00.

  14. James

    August 6, 2007 at 6:05 am

    The Home Depot link for the “cheap sprayer” that Luis mentioned in his post no longer works. Does anyone know what product he was talking about? (air pump sprayer, maybe??).

    I have an unusually long evaporator drain line that goes into the wall of the garage, under the floor of the garage and then out the other wall of the garage. I’ve flushed it with a garden hose before — this gets water everywhere because I’m just manually holding the hose to the drainpipe — but I’ve got a particularly nasty clog now that the usual garden hose flush only fixed for about 24 hours. So I’m desperate for a better means of flushing the thing.

  15. James

    August 8, 2007 at 7:16 am

    I tried the cheap sprayer fix, but if we’re talking about those cheap 3-4 gallon plastic pesticide sprayers you pump air into, it didn’t work — just not enough air coming out. I ended up duct-taping the garden hose tightly to the cut in the drainpipe (before, I had just used the “jet” setting on the garden hose sprayer nozzle and held it against the drainpipe opening). Yup, water sprayed out through various parts of the duct tape, but there was still more than sufficient water pressure being forced down through the drainpipe, and a mass of goo was flushed out of the other end of the drainpipe in a river of water.

  16. Shawn

    August 9, 2007 at 1:30 pm

    I recently had my inside and outside AC units replaced. I have one main condensation drain that goes outside the house. Under the inside AC unit the service company used a product called “MASTIC” to protect the sheet rock, 2×4’s, etc. People looking to repair their pans may want to use this product since is a liquid pliable substance that will dry hard like an epoxy and waterproof whatever you want to protect.

    Searches on the internet indicate you can get it in gallon size containers fairly cheap. I’m looking at using this product now to seal some cabinets under my sinks just in case the pipes leak.

  17. Mark

    August 9, 2007 at 4:32 pm

    Great tip. Shawn. I’ll look for some for next time I change my filters.

  18. dameon

    September 1, 2007 at 2:07 pm

    i have a primary drain clog. do you know of a way to blow it out with out cutting the pipe. the primary drain has a t connection from the unit to the drain pipe. when i blow it out it takes the path of least resistance, back into the unit. not down the clogged pipe. i have a co2 charged device to blow it out. thanks dameon

  19. Mark

    September 1, 2007 at 8:41 pm

    If you look at the picture, you’ll see that I cut into my pipe and installed an elbow joint for just that purose. I blew the line out before I put the elbow in, so the air could only go one way.

    Don’t worry too much about cutting your line if it is PVC. It’s easy to reconnect with a short sleeve and PVC cement.

  20. Lee

    September 4, 2007 at 5:37 pm

    Our second floor condo unit is not condensing/dripping outside. The water sits inside in the pan and does not drip out. We end up going downstairs and using a shop vac to suck out the sitting water. We also tried using those algae tablets and liquid, but none has pushed the condensation downstairs. Maybe there is a clogged pipe somewhere? Does anyone have a recommendation? Is it safe to use a snake to try to unclog an a/c pipe, and if yes, where should we snake it from (outside)?

  21. dan

    August 7, 2008 at 3:20 am

    Anyone know of a source for clear PVC pipe insert and/or retrofit to my current PVC drain pipe arrangement that I could install to clean out gooseneck with a baby bottle brush or the like? A neighbor told me their new AC/Furnace installer put one in. I had clogged gooseneck drain from condensation unit yesterday, gallons of watter on the floor that could not get throught the drain pipe. After shop vac time and taking cover off AC condenser unit, I found a flexible plastic pipe, fit it a few inches into top of drain and blew it clear enough to drain. But this took a long time. These days there has to be a simpler solution. Thanks

  22. Rich

    August 10, 2008 at 7:25 pm

    A great technique is to find where it is supposed to be dripping and hold a shopvac (cleared for wet use) on the output and it will suck out the algae and free the obstruction.

  23. Tony

    September 8, 2008 at 12:40 pm

    My secondary overflow was flowing from day one on my newly constructed house.
    I finally checked out my unit (after 2 plus years) and discovered that the installer didn’t put any slope to the pipe coming out of the unit. In fact, the pipe was sloping in the wrong direction entirely. All condensation was moving out of the secondary overflow to the side of my house because it couldn’t escape the primary.

  24. Lee

    September 27, 2008 at 4:40 pm

    Interesting that somebody else in Phoenix had a problem with a too-short drip pan. I’ve got a soggy bedroom ceiling since my primary drain plugged and the drip pan is too short.

  25. Sean

    October 3, 2008 at 9:34 pm

    For future refrence that condensate pipe should have a trap on it. This traps allows water to drain even when the A/C is on. When the A/C is on there is negative pressure inside the airhandler. Without a trap it will suck the water up not allowing it to drain from the pan.

  26. Cool Air USA

    November 24, 2011 at 4:50 pm

    i recommend to flush drain line once a year by contractor and every 60 days run bleach in pipe


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