A/C Condensate Drain Piping Flood

[Lordoftheflies]

So my mother called me up and said she had a flood seeping into the closet next to the boiler/ac room.

I went there and saw no visible puddle. It was like 83 degrees in the 10 year old apartment building in harlem so I turned on the A/C.

Checked the boiler to see if it was popping the PRV but the pressure and temps were fine.

Ate dinner and then came down and looked again and there was a huge puddle. It was cold to the touch.

I figured it had to be the a/c condensate and had to get under the unit with almost zero room to work with.

The drain for the a/c was all clogged up with mud and much to my surprise (I guess by now I shouldn't be surprised at shoddy workmanship) the 3/4 pvc pipe moved when I was trying to scoop out the mud.

Well wouldn't you know they didn't use pvc glue on the condensate drain except for where it came out of the AC unit. All the elbows rotated.

So I redid the entire thing the next day (it was late) and here are the pics.

Original setup:

View from under the AC unit after I redid the piping.

There was no vent on the drain side of the original setup. I put the cap on backwards so you can't accidentally cap it.

Clear tube trap so you can see if it's all gunked up. Easy to clean too. Put 2 unions just in case I ever need to take it apart.

 

[Stuff]

You could also add an overflow sensor to shut things down before the next flood.

 

[Sponsor]

 

[Lordoftheflies]

Yep that's next. Was thinking about this one:

 

[Addison]

So my mother called me up and said she had a flood seeping into the closet next to the boiler/ac room.

Ihere was no vent on the drain side of the original setup. I put the cap on backwards so you can't accidentally cap it.

This may be a terrible question: but what is the purpose of the vent on the drain side?

 

[Lordoftheflies]

To help it drain easier. This was installed on a negative pressure ac (the air is sucked up through the bottom of the unit) and it causes the water to get sucked up from the drain pan as well.........The p-trap has enough water in it to prevent the ac unit from trying to suck air in from the condensate drain and the vent on the drain side vents the line.

This is not connected to a household vent so no risk of sewer gases coming up.

 

[Addison]

Makes sense. I have a positive pressure set up (blow through). I never noticed a vent. Is it necessary on a blow through?

 

[Lordoftheflies]

I do not believe you need it for positive pressure, no.....