Florida. Sandy soil, no basement, house on a slab. The HVAC air handler is in the attached garage at the front of the house. The pipe that carries the condensed water goes under the house, all the way to the back -- I have no idea why it does not exit the side of the garage, which would be a much shorter run.

Once or twice a year, this pipe clogs, I don't know what, maybe algae? Water backs up and collects on the garage floor.

In the past, I have managed to get it flowing again by blasting compressed air through it from the air handler end. I'll need to do that again, today.

In terms of preventive maintenance, I have been informed that pouring some vinegar down the pipe once a month or so will keep it clear. I have had other advice telling me to use bleach. And still others have suggested a harsh sulfuric acid drain cleaner.

Does anybody have the correct answer?

I use bleach in mine a couple times per year, and have never had any issues with algae.

I've used both, at different times, vinegar and bleach. Shop Vac was less than impressive.

On jobs where the drain line run is long, I prefer to install a condensate pump and that keeps the velocity up and flushes the line. Diluted Bleach will do the trick. Use some google foo to locate condensate pan treatments that you place in the pan / coil. If it has been sometime since the coil was cleaned, doing that will help keep the drain run clear,as bio growths will continue to buildup and will just keep the stuff growing. If conditions are bad enough, look into a UV lamp.

I run bleach through mine a few times a year and if it does back up (like it did a week or so ago) I have a gizmo I can attach to a garden hose that I can blast out the condensate line.

Diluted bleach. They also sell tablets that are supposed to prevent the stuff from building up. The downside was that the house smelled like an indoor pool for a day. Small amount once per month works. Also changing or cleaning the filter once per month helps as well.

Same conditions here with the same problem with my old system. I would us a 50/50 mix of bleach and hot water. I would put in enough so i could smell the bleach at the discharge and the the condensation would dilute it way.

They also make an adapter for shop vacs to connect to the output so you can suck the stuff out but i just did the compressed air route as well.

Since i had a new system installed i just treat it once a year.. No problems so far.

Find some of the chlorine tablets they use in pools and break them up small enough to fit in the pipe . Throw a few pieces in every few weeks and the pipe will get a constant treatment . Just enough to keep anything from growing .

quote:

Originally posted by hvactech:
On jobs where the drain line run is long, I prefer to install a condensate pump and that keeps the velocity up and flushes the line. Diluted Bleach will do the trick. Use some google foo to locate condensate pan treatments that you place in the pan / coil. If it has been sometime since the coil was cleaned, doing that will help keep the drain run clear,as bio growths will continue to buildup and will just keep the stuff growing. If conditions are bad enough, look into a UV lamp.

^^^ This

Tapping into the sewer line will cut down on clogs. As you don't get insects/spiders and crap in the line from the outdoor enviroment.