"Found water on floor near furnace."
Column #850 06/11/11
On The Level
Q. During last week’s hot and humid spell we noticed some standing water under and around the furnace in the basement. Couldn’t see a pipe leak. What might this mean? Can we turn the air back on or is it an electrical issue with the A/C? Do you think we need to call someone? What do you think this is? Thanks for any thoughts you have.
A. The quick answer is that your air conditioning 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 has to dispose 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 outlet. 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 that sits on the floor next to the unit. It acts like a little sump pump dedicated just for your air-conditioner’s condensate 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 tubing and you’ll see 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 clear 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, ceilings, 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. And you’ve got company coming over at 7. You can’t for the life of you figure out what’s wrong. The thermostat is set at all the right settings, the circuit breaker’s not tripped but nothing is happening and the chances of you getting a service call before the guests show up is nil. Sometimes the catch pan under the unit has a water float switch and if the secondary drain of the pain is clogged it too will shut the system down. Go into the space where the system is located and look to see if you see water in the pan and clear the drain if it does. Or take your screwdriver in hand and rap the side of the condensate pump to kick it into motion. It works more often than not.
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