Dr. Kool‘s

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Condensate Drains

Air conditioning serves two purposes—cooling and de-humidification. In the process of cooling, moisture is removed from the air, and passes into a sewer or some other suitable receptacle. If the condensate drain gets stopped up, the water may overflow. There are safeguards, but they don't always work.

If the air handler (or furnace) is in the closet, and on the first floor, a condensate overflow is not nearly so bad. Bare feet often find the problem, before there's any visible evidence.

Water Through the Ceiling

But, where the air handler is in the attic, water may spill over, and come through the ceiling. If the problem is caught early, the damage will be minimized, but more often than not, the drywall will be stained, and have to be repainted.

But, what happens when the house is empty, and the overflow occurs? One of my customers returned from vacation, and found the entire plasterboard ceiling had caved in. Another customer returned, and found $5400 in water damage.

Building or Remodeling?

If you're building a new house or remodeling, my advice is to never put your water heater or AC air handler in the attic. They should be placed in a closet, and on the first floor. Let me qualify that. It's okay to place a source of condensate or water above your attached garage. Any water related damage will usually be minimal.

Another alternative is to place it in the attic, above your first floor bathtub or toilet. That way, when water comes through the ceiling, only the ceiling will be damaged. What I just said was meant to be a joke, but I am trying to make a point: water through the ceiling is no joke.

Drain System Design, and Safeguards that Often Work

For closet installations, a float switch may be in place. If so it will turn off the compressor when a drain starts to back up.

For an attic installation, there are two drain systems. During normal operation, a hidden primary pan collects the condensate, which flows into the sanitary system. If the primary drain line gets stopped up, the water spills over into a visible safety (secondary) pan.

Condensate in the secondary pan flows through a separate drain line, and empties out the soffitt or gable end of the house. You will see water dripping from the edge of the house, and that should tell you to call an AC repairman.

Sometimes a homeowner will ignore the safety drip, and allow it to continue until the secondary drain line also gets stopped up. When that happens, water may come through his ceiling.

If there is a float switch on the safety pan, rising water should shut off the compressor to prevent additional condensate from forming.

One more thing: sometimes an evaporator coil will freeze up, and then melt. When that happens, water can go anywhere it wants, and all the safety measures in the world won't protect your ceiling.

It's Only a Matter of Time

If your evaporator coil is in the attic, you should expect that moisture from the system will someday come through the ceiling. You should determine, beforehand, where water might come through. Then make sure your Steinway or computer is not in that location. The AC contractor has no control over where you place your belongings, and cannot accept responsibility for that sort of consequential damage.

What Can You (the homeowner) Do?

In my article on Air Filters, I point out that a regular schedule for changing filters will help prevent drains from getting stopped up, but that's not all.

I suggest you go outside, before any problem occurs. Visually locate the overflow drain line which protrudes from your soffitt or the gable end of your house. On an ongoing basis, pay attention! If you see water dripping, call your AC repairman.

It's a good idea to periodically pour bleach into the primary drain pan. This requires that there be an open tee in the PVC drain line. If there is one, the tee will be near the evaporator coil. Or your AC man can install one.

When the Drain Gets Stopped

Call your AC repairman, and he will clear the line. I carry a fire extinguisher loaded with water under pressure. I find that to be superior to using compressed air. Water is more erosive than air, and tends to flush away more debris.

Be kool and keep dry,

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Dr. Kool

p.s. If household humidity is your concern, you might want to read my article, Dehumidification.

p.p.s. If you're not yet registered, by all means do it now—it's easy, and it's free!

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