AC Condensate Drain - Vent?

Nothing like the high-humidity early start of summer in FL to show you the flaws in your AC systems...
I found it 'raining' in the engine room the other day as the salon AC condensate drain was not doing its job, and the water was running down into the ER. I used a garden hose connected to hot water to flush the line but it was never clogged. Still was not draining the way it should, so I took a closer look at how it was routed.

PO had attached the hose to the ER ceiling for a run of about 8 feet, then down the aft bulkhead to the overboard fitting which is above the water line. A few small 'dips' in the hose plus some unnecessary unions meant that the gravity flow of water just couldn't get through the way it should. Very little slope, if any, overall for that 8 foot run. I rerouted the hose to give it some slope and remove the low spots. It's working much better. However, the drain pan does not stay as dry as I'd like nor does it stay as dry as the other systems aboard.

I am thinking about venting the condensate line to put some "air behind water" as is common in household systems. I wonder if adding a simple standpipe about 3" tall at the AC drain pan connection would help? I've never seen this on any boat we've owned but wonder why / why not...

I found with mine the most important thing is to get some vertical drop as close to the A/C unit as possible. One of mine drops a few inches from the pan into the engine room, then even with an almost level run for a while until it drops down to a thru hull, the pan drains well. Standing water is no more than a 1/2 inch, and I think improving that would require tilting the A/C unit a bit.

What does your A/C drain to?

Yes, maybe try shimming up the opposite end from the drain to give the condensate pan some help in getting the water to the drain hole. May not take a lot. Just loosen the screws on that side and slide some wood shims in to see if it helps or not.

rslifkin said:

I found with mine the most important thing is to get some vertical drop as close to the A/C unit as possible. One of mine drops a few inches from the pan into the engine room, then even with an almost level run for a while until it drops down to a thru hull, the pan drains well. Standing water is no more than a 1/2 inch, and I think improving that would require tilting the A/C unit a bit.

What does your A/C drain to?

Click to expand...

From the pan it drops straight down a few inches into the engine room, then goes to an overboard discharge.

markpj23 said:

From the pan it drops straight down a few inches into the engine room, then goes to an overboard discharge.

Click to expand...

Sounds similar to my setup then. Does the pan have a drain on more than 1 corner? If so, you may want to connect more than 1 and tee them together. The unit won't be 100% level all the time, so it may drain better that way.



I also found that I had to work to avoid a slight rise in the hose when it left the drain pan and made the turn down through the floor. Getting rid of that slight rise made a big difference in how low the water level in the pan stayed.

Comodave said:

Yes, maybe try shimming up the opposite end from the drain to give the condensate pan some help in getting the water to the drain hole. May not take a lot. Just loosen the screws on that side and slide some wood shims in to see if it helps or not.

Click to expand...

It's already shimmed up on the opposite side so the pan draining is not the issue. With the hoses disconnected in the engine room, the pan would completely dry out.
Even after fixing the slope there is apparently some resistance to gravity flow as the pan has water in it most all the time. Not overflowing, but not dry either.
I've dumped hydrogen peroxide through the system also after having done a hot water flush.
All this leads me to believe that adding a standpipe as a plumbing vent would help.

Besides making sure all "runs downhill, add:


https://www.amazon.com/AC-Safe-Pan-...ix=air+conditioner+pan+tablets,aps,608&sr=8-2


They won't unclog you line, but they will keep you line from clogging. Keep in mind that keeping you pan clean prevents Legionella...

hturner said:

besides making sure all "runs downhill, add:


https://www.amazon.com/ac-safe-pan-...ix=air+conditioner+pan+tablets,aps,608&sr=8-2


they won't unclog you line, but they will keep you line from clogging. Keep in mind that keeping you pan clean prevents legionella...

Click to expand...

amen!