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We noticed some standing water under and around the furnace...
9 June 2007


Q.This morning we noticed some standing water under and around the furnace. Not a lot, but noticeable. What might this mean? I was able to easily mop it. Do we dare turn the air back on (electrical issue)? Or do you think we need to call someone first? C ould this mean there's a hose issue? Thanks for any thoughts you have.

A.The quick answer is that your condensate drain system is probably clogged. Condensate is the name given to the moisture that has been condensed out of your household air during air-conditioning and now that the unit has turned humidity into water it ha s to get rid of it. If the drain system from the unit gets a clog in it that water will spill out onto the floor.

Here's how you might take care of the problem before you spend money. There is a thing called a condensate pan the lives under the coils inside of your air unit from which there is usually a white plastic pipe that leads from that pan to some sort of ou tlet. It could go to a floor drain that leads to a sump pit or to a little electric device called a condensate pump. That’s a small box like device on the floor next to the unit. It acts like a little sump pump dedicated just for your air-conditioner’s c ondensate and when it malfunctions will overflow onto the floor. It has a float switch in it that can get hung up.

Bang on the side of the condensate pump’s side with a screw driver handle to try to free it up. If it does the trick you’ll hear the little pump motor run and frequently the line leading away from the condensate pump is a clear plastic tube and you’ll se e the condensate traveling through it to its outflow point.

Failing that or if you don’t have a condensate pump but just the condensate drain line that goes off somewhere, look for a little "trap" on the condensate line near the unit that looks like a little "U" in the pipe. That is usually where the clog occurs. You'll need to dismantle the pipe at a joint near there to clear the blockage. Good heating and cooling installers leave a joint near the trap unglued or a small pipe extension above it with a removable cap on it so one can open it above the trap to cle ar clogs-- they happen that often and are that predictable. You can use a bent coat hanger as a tool-- the pros use compressed air to blow out the clogs. I've used my own lungs to blow it out-- disgusting, but gets the job done.

A tip that most HVAC service providers suggest is to pour about a half a cup of liquid laundry bleach into that little trap preferably at the beginning of the season-- which is now. If you can and are skilled enough to open the chassis of the air unit to access the condensate pan itself then I recommend pouring some bleach in there. If condensate remains in the pan it can become swamp like with wet dust and microbial growth. That mess can also create an odor known in the industry as “dirty sock syndrome ” and you’ll know if you have it. If the pan is tilted incorrectly and doesn’t drain properly it can increase the humidity in the house creating interior mold and mildew issues.

Frequently, if the air unit is located above the lowest level of the house, the condensate pump is wired to the controls of the system. The purpose of doing that is to prevent a condensate spillage onto finished floors or to prevent damage to drywall, ce ilings, insulation etc. The condensate pump will sense its malfunction and shut the whole system down. Murphy’s Law dictates that this will occur at 4 O’clock on a Saturday afternoon when it’s 95º in the shade and you can cut the humidity with a knife. A nd you’ve got guests coming over at 7. You can’t for the life of you figure out what’s wrong. The thermostat is set in all the right settings, the breaker’s not tripped but nothing is happening and the chances of you getting a service call before the gue sts show up is nil. Then is the time to go to the unit with your screwdriver in hand a rap the side of the condensate pump to kick it into motion. It works more often than not.

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