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A/C drain hoses

Discussion in 'Technical Discussion' started by aircar, May 14, 2017.

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  1. aircar

    aircar New Member

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    I have had a lot of trouble with drain hoses on A/C air handler units. I have heard several theories about how to keep the hoses clean, compressed air from unit, vacuum from the drain end of the hoses, etc. I would appreciate any suggestions from people who have had success in this area.
  2. Pascal

    Pascal Senior Member

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    The problem is that the **** boat builders and installers dont use big enough hoses and worst run them without enough slope to drain. It drives me nuts... almost every boat I ve owned or run had the problem on at least one or two air handlers

    Wet carpets, drips from the ceiling... lovely.

    And to make things worst the drain holes in the pans are usually impossible to reach because the evaporator blocks the way.

    That said what I do is stuff a flexible hose in the pan hole with some shop towel to seal and blow thru it Cruisair pans have 2 holes often teed together so you need to block the second hole when blowing

    The best air handlers I ve seen so far are from Flagship marine. They built them with a slope in the pan and use larger fittings. I ve just redone my 53 hatt with 2 chillers and 5 air handlers from flagship and made sure the hoses have enough angle

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  3. rcrapps

    rcrapps Senior Member

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    Where the drain hose lines bend, they usually fold flat and clog. Hot air gun and nylon 90 fittings help here. Usually 5/8' hose.
    Your probably already having condensing station water flow issues or will soon.
    If it's an old boat, plan several nights in replacing all the hoses with nice radi or fittings.
  4. wdrzal

    wdrzal Senior Member

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    Don't forget there must be a trap on the evaporator drain line. (because of the differential pressure in the air handler) If not, the pan will fill, then it will only be able to drain when the air handler shuts down , If it doesn't over flow first.

    Get some biodegradable foaming evaporator coil cleaner and spray down the evap. Some times you can get away with a reversible shop vac. Suck on the outlet, then reverse you vac to blow towards the evaporator , you may need to repeat this several times. You may also have to add water to the evaporator pan to use as a flush liquid. The cleaner will self rinse off the coil when you run the AC. But if you have access I use a 2 gallon garden spray pump up bottle to apply the cleaner and rinse water.
  5. Pascal

    Pascal Senior Member

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    Never heard that one before and I don't see how there can be differential pressure in an open space such as the pan. If you a trap in the line, all it will do is trap dirt and clog up.
  6. d_meister

    d_meister Member

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    I ran a 55 Nordhavn for a while that had overflowing evaporator pan issues from Day 1, I was told. The worst ones were in the pilothouse settee and under the pilothouse console. My predecessor had worked on it in La Paz, MX. and he was helping me deliver the boat from the PNW when we tackled the issue again. It was never a problem of the line restricting, we found out after a lot of blowing and messing around. We finally fixed it by putting a "T" into the drain line with a vent tube higher than the evaporator. Just like a house, drain lines need vents.
  7. Capt J

    Capt J Senior Member

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    Pour a good amount (a liter) of white vinegar in the a/c pan once every month or two......this helps keep the lines clear.
  8. wdrzal

    wdrzal Senior Member

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    The drain pan and coil is either located before or after the blower in a air handler & duct system. The return air side (before the blower) is a lower pressure than what ever the standard barometric pressure is in the room. In this case, without a water trap the blower will suck air up the tube making it harder or impossible to drain the pan depending on several factors. Also without a trap, air or fluids can be sucked up the drain tube if a trap is not present.

    If the coil & drain pan are after the blower, the pressure is higher in that area. The pan will drain without a trap but you will be literally blowing cooling capacity down the drain along with the water.

    If your worried about dirt clogging a trap you should address your intake air filtration system.
  9. aircar

    aircar New Member

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  10. aircar

    aircar New Member

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    I appreciate your responses. It's one of those things. I was told today to pour a little bleach in the pan. Good or no?
  11. Pascal

    Pascal Senior Member

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    On all the AH I ve dealt with the blower is mounted to the evaporator and pulls air thru it. The pan is under the evaporator but open all around. There is no way to develop any significant low pressure that would affect the pan

    I don't like using bleach unless I have to. It smells and is corrosive. Maybe it s ok but I ve never done it
    It s so much easier to have an oversized hose with enough slope to get to the sump without any low point
  12. Capt J

    Capt J Senior Member

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    I find bleach to be too corrosive and it eats up the aluminum coils on the air handler sometimes if it sits in there too long and off gasses. You're better with a very mild acid......IE white vinegar and it's just as cheap as bleach anyways......OR they make those tablets specifically for a/c's.

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