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Douglas, HVAC Technician
Category: HVAC
Satisfied Customers: 3089
Experience:  Manufacture Rep for Major Brand, Technical Trainer, NATE
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Why is my heat pump leaking water?

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Why is my heat pump/air conditioner leaking water onto my basement floor? I assume it is condensate since the puddle is not that large. My unit is many years old, installed when the house was built in 1993. I changed filters but am not sure I have the right size. I took out 25 x21 x1's but can only find 25 x 20's in local hardware//bigbox stores. Help.

Most likely, it is indeed condensate as you suspect.
It may be one of several things.

  • Over time a coil may get dirt on it and water does not "sheet" as well as it once did. It can form a drop if it has a chunk of dirt or a dry spot on the coil. Especially if your filter doesn't fit correctly.
  • If it's that old, it may have a metal drain pan which may be rusted through and can leak. Even a plastic pan can have a crack in it.
  • If your unit has frozen up, when it thaws, it can drop chunks of ice into the lower end and that melts.
  • The drain could be slow and just need blown out.
  • The refrigerant line (the large insulated one) may just need the insulation repaired, it could be sweating and dripping
  • The condensate drain can also sweat if the water inside is cold enough.

Is there an auxiliary drain pipe?
You may have to open the air handler door and inspect the drain. There should not be much water in the pan (a little). If it is deep your drain is either restricted or not properly trapped. If it's metal, look for rust, if it's rusty, it may just need a new drain pan. You really can't see the part of the coil that would get dirty, it would be on the incoming air inlet side of the coil.

Douglas and other HVAC Specialists are ready to help you
Customer: replied 6 years ago.

It sounds like it could be the drain. The water seems to collect around the base of the unit and does not appear to be dripping from the refrigerant line. Have no idea if there's an auxiliary drain - I view this thing as a magical metal box that heats & cools the house without much interference from mortals! But it has been quite a while since any service was done on the unit so it may be time to call in a local technician. At least I now have some idea of what problems I am having and can ask intelligently for repairs. I thank you for that.

If you can see the end of the drain (maybe it goes to a floor drain). You can try to attach a shop vacuum to it and see if it pulls a bunch of goop along with the water. Sometimes that does the trick.

Customer: replied 6 years ago.

No floor drain visible - house is built on a floating slab. No shop vacuum. You are dealing with a technically inept grandmother. But another thought to have in mind for a repair person.

A technician uses a device called a gallow gun. Think of one of those CO2 cartridges used for whipping cream or in some pellet guns. They use this to blow the drain out.
I would probably suggest getting it serviced while it's only a small problem. Use a reputable HVAC service company and if you don't know any ask your friends and family. The yellow pages are full of "hacks" and "cheats".