Wednesday, August 16, 2017

More Joys of Home Ownership

Yesterday evening, as I was gathering thoughts to put together a post, I got to hear one of those things that every homeowner knows and dreads, "there's water coming out of the air conditioner in the garage". 

Thankfully it was fairly routine, but it did suck up the few hours of evening. 

By nature, central air conditioners suck in air that's warmer and damper than the air they condition and exhaust.  The humidity condenses on the cooling coils, then drains down to a trough where it's routed to a PVC pipe and outside.  If you've ever had or seen a window-mounted air conditioner, you know they just dripped the water outside.  A central system is usually located somewhere more like a living space, garage or attic or something else like that, so they pipe the water out of the house.  Since those pipes are carrying water, it's common for them to fill up with algae and cleaning them out is routine maintenance.  We pour some bleach into that pipe and clean it out about every 90 days.  Less frequently, the water trough below the coils needs to be cleaned out, and that's what was overflowing and dripping on the floor.  Some disassembly, some time with the wet/dry shop vac, and it's cleaned out. 

I found this picture online - it looks like a brand new set of evaporator coils, but it shows the design of the water collection.  Put that in a metal box the size of the bottom tray and that's the space to work in.
The air flow is from the bottom up, through the inclined evaporator coils that look like car radiators, and the water that condenses on the radiator fins drips down into that tray at the bottom. 

And by the way, there may be exceptions but I say don't buy a house with the air conditioner indoor unit in the attic, because someday it will drip water, and having that water coming through your ceiling is a worse thing than having it drip onto an unsealed concrete floor, where it absorbs into the floor and drains through it.


  1. We had that a/c 'snot' develop last month - we laughed and laughed. Our condensate drain has minimal slope to the exterior, so at least once a year, we have to clean it out. We used to insert a garden hose and blast it out, but tried using compressed air from a compressor and it seems to be more effective getting more of it out.

    My condolences for the trouble - at least you didn't have to acid wash the coils, now that is a lot of bother.

  2. Mine drains through a 1" PVC pipe that travels about 15 feet to the outside. We had a problem with this once because it clogged up and the backed-up water drained onto the finished basement floor causing some expensive damage.

    After that incident, I modified the drain slightly by adding a PVC valve right next to where it exits the condenser and a hose attachment just downstream of that. I simply attach a garden hose to the outside spigot and the other end to the attachment. I then shut off the PVC valve and turn on the water. It blows all the gunk out in just a couple of seconds. I do this every spring and haven't had a problem since.

  3. "Course, you've also got condensation on the condensate pan, so you put another below that. And a float switch in the primary to cut off power if the water in the pan gets too high.

  4. In many regions it's a code requirement to have a "high water level" switch that shuts down the A/C if the water level in the condensate pan is too high. It's usually mounted on a condensate drain outlet via a PVC T. Some have an LED to indicate a high water level condition. I surmise the water level cut off switch became a building code item because many homes have been flooded as homeowners were away for extended periods and flooding occurred inside the living spaces In South Floridas summers a few gallons of water can be produced every 24 hours. This is a timely article as I just replaced a 25' condensate drain line that was plugged solid and no amount of air pressure would clear it.
    The residential fan coil units condensate drain designs are all by the same monkey design teams. Homeowners an are forever dealing with this defect and A/C contractors are making big $$ blowing down drains and selling anti fungal tablets to rest in the drain pan. Each time I have to deal with a plugged condensate drain I swear I will design an improved method of condensate disposal but that never happens. The other thorn in my home is a GE refrigerator that also leaks onto the floor. It's another monkey design for handling defrost water where the drain is not mounted at the lowest level of the collection trough. After a few months of defrost cycles the water collection trough freezes solid to the top and the next defrost cycle the water overflows to the floor of the freezer section and out a minor gap of the door gasket onto the kitchen floor. Designed by Monkeys.

    1. The system has one of those switches. It's either in the wrong place or it just doesn't work.

      One of the videos I saw has a guy hooking up his vacuum on the outside of the house and sucking the crap out of the tube. I think I could pull my air compressor to the inside clean-out trap and blow the goop out, but so far the practice of pouring some bleach in the PVC pipe (1", like yours) every 90 days or so when we change filters has kept it clean.

      In my mind I keep expecting to find a miniature Burmese python or some other snake stuck in the pipe.

    2. SiG, AC outfits are now recommending white vinegar instead of bleach. No idea why, but I suspect liquid chlorine or chloring fumes attacking something important might be it; few installers think far enough ahead to put a trap in the condensate drain.

      RE: air compressor & blowing out line. Careful with that - I've seen drain lines that were dry fitted to check the run and the installer never glued them together. Air pressure could separate sections inside a wall, or force liquid content through a joint somewhere. Vacuum is better. In FL a medium mesh over the outlet keeps the little lizards out, I've seen them plug lines.

    3. Interesting. I hadn't heard of white vinegar instead of bleach.

      Putting a piece of screen over the line is something we got taught long ago. Same as leaving a nozzle on any hose to keep the lizards out of them.

    4. The reason for vinegar over chlorine is that the acidity of the vinegar kills the slime mold ('cause that is what it is) better and more cleanly than the bleach. it also cleans the drain line by actually destroying the molds structure, something that the chlorine bleach doesn't.

      Having worked with such items (and industrial icemakers and such) where slime molds can be an issue, I have found that vinegar does indeed work better. Adding a few drops of detergent the next day or two later can also be very beneficial, as it helps clean out the drain pipe.

      Or you can flush it with a slug of Windex, which also cleans the residue.

  5. G.B. If the float switch isn't in the area where the water collects then you can move it so that it works. I've seen sections of sheet rock fall from the ceiling due to a stopped up drain. Also Home Depot has "Air Conditioner Pan Tablets" that will last longer than bleach does. Good Luck.

  6. My landlord's new house (built in '04) has that attic A/C setup. Lots of problems showed up during acceptance then. I forget why, but the builder's repair crew disconnected the A/C drain hose that ran into one of the upstairs bathroom sinks drain pipe. Hot day, air was on, and as I was leaving later that day, found water dripping out of the garage ceiling. Bedroom carpets were wet, bathroom floor had water running out of the sink cabinet.

    They pulled the carpets up, and set up several large fans (bathroom served two bedrooms). So many problems. A bunch of owners ended up suing the builder for gross stupidity, essentially. 600 unit complex. Builder went bankrupt, I was told. Construction workers didn't speak English, and I was told by a PG&E guy that the (non-English speaking) electricians were being paid $8/hr. (the not-so-great state of Commiefornia, natch)

  7. While PVC is not harmed by bleach, it is my understanding that chlorine (as in bleach) has a corrosive effect upon many metals, including copper:

    Bleach also causes a corrosion of the copper surface. This is an actual change in the surface of the copper that breaks down the material. Copper corrosion can be caused by pollution and the exposure to moisture. While copper is known to have good corrosion resistance, bleach accelerates the process and can cause damage to copper pipes and fittings.

    (One major gun manufacturer actually had barrels fall off of their revolvers. An investigation ensued, and they found that the chlorinated esters used in their machining oils was causing stress cracking in barrel threads. When combined with the gun owners' use of cleaning and lube compounds containing chlorinated esters, the barrels simply sheared off at the weakest part - the threads. Like most aircraft makers, the company learned to forbid chlorine-carrying compounds on the manufacturing floor, to prevent a recurrence.)