Pouring bleach down AC lines to clean it out

Hello Everyone,

Are the pvc pipes that are open and vertical in these two pictures where I should pour my bleach into, to clean out all of the mold etc. that might have formed. I know I need to do this about once or twice per year.

 

I recommend using Hydrogen Peroxide instead of bleach. Hydrogen Peroxide does just as good of job dissolving any build-up and it's less expensive and you don't have to worry about getting bleach on your hands or clothing. Buy a cheap plastic funnel like used for pouring engine oil and buy 4 or 5 32oz bottles of Hydrogen peroxide from Walmart for $1 each.

Every few months during A/C season turn Off your A/C at the thermostat and pour a couple cups of Hydrogen Peroxide into the PVC stub-up for the primary condensate line. Wait about 15 to 20 minutes before turning the A/C back On again at the thermostat to let it soak in and dissolve any gunk in the condensate line.

 

Should those pvc pipes be capped at all? they are just sticking up fully open.

 

No, leave the stub-up open to the atmosphere so it will drain properly. The open ¾" PVC standpipe acts as a vent to the atmosphere and must remain open and not be capped. This open vent is much like allowing air into the bottom of a large bottle you want to dump the liquid out of. It's like opening the vent on the back side of a gasoline can when pouring gas in a lawnmower. It needs a vent to allow air in to fill the void where liquid was so the liquid inside can flow out easily and unrestricted..

Some HVAC condensation lines are installed without a P-trap. A P-trap is not needed in a system when the A-Coil and its condensate line is on the positive side. In this setup the condensate line only needs to have an open vent to the atmosphere/attic. If however a P-trap is installed for code purposes it must be vented on the coil side. It is important that this vent pipe not be capped because condensate water will not drain properly.

Pressurized blower air from the A-Coil cabinet, along with the open standpipe vent helps push the water out of the condensate line, which in many areas is drained out underneath a lavatory sink, below its drain and above its P-trap. If the standpipe vent is capped the vent air can't help push the water out - and the sink where the condensate is to drain out can't drain well because blower air pressure would block water from draining out of the sink's bowl at the small gap of the drain stopper. The ¾" PVC vent pipe for the primary condensate line is to be left open to the atmosphere/attic. The small amount of cool air released into the attic or wherever from the ¾" diameter PVC open vent pipe is insignificant and trivial.