adding a condensate trap to a vent pipe that isn't pitched properly?

mthmlf84

I just installed a triangle tube instinct 199 btu boiler and the technician from the gas company inspected it in preparation of hooking up the gas. He says there is a problem with my vent pipe which I should have understood when I first installed. Space was tight and we hung the boiler a bit too high because we were afraid of not having room to put the hydraulic separator above the floor. This and ignorance made us not pitch the 3" pvc vent pipe properly when going out of the house, and it created a trap the condensate will accumulate in, causing the boiler not to fire anymore, etc. See "current" on the drawing.

"proposed" is what we discussed to fix it, but I want to make sure I understand and correct if needed. The idea would be to elbow the pipe down in the section where there's a trap, tee off of that with a 3/4 drain line sloping towards a suitable drain location (my sump is not far, or a condensate pump), then 90 elbow the pipe back up and down again.

sorry bout the amateur language, I'm sure there's a name for this and clear answer to wether or not this design will leak the flue gazes straight into my basement, that's why I'm asking. thanks!

JUGHNE

You could just go the the lowest spot where the water collects and drill and tap a 1/2" pipe thread hole.

Install a 1/2" male X barb for1/2" inside diameter tubing fitting.
Then make a complete circle with the tubing that is about 6-8" in diameter.
That is your trap.
The water will drain, fill part of the circle and keep exhaust gases out of the basement.

The water should go to a condensate water neutralizer, as your boiler cond water should also.

mthmlf84

thats awesome thank you

mthmlf84

i understand the trap idea better now thanks, i was thinking i had to make the 3" pipe go up and down but it's not necessary if I can branch out from the lowest point of liquid accumulation zone into smaller diameter pipe or tubing, make a trap there, makes sense, very cool

HomerJSmith

That's first for me, having a running trap in the exhaust vent. I have always pitched the vent 1/4" per foot up from the boiler to the outside. The condensate that forms runs back to the boiler and exits out the boiler trap into the condensate neutralizer, then in to a condensate pump or drain. Am I learning something new here?

JUGHNE, is a solution, but should be at the lowest point in the exhaust vent run, depending on how the vent is pitched, then you have to deal with the acidic condensate.

JUGHNE

I had a boiler that used "Ultra Vent" piping for a 87% partially condensing exhaust.

The Plastic Ultra Vent was recalled and SS supplied for the exhaust.
They included a short 3" OD section with a 1/2" bottom tap for cond drain.
This piece was placed just before the horizontal exit thru side wall.
The tubing was curled/trapped and ran back to drain.

The entire run was sloped to drain back to the boiler, but the trap picked up a lot of condensate that would have been spewed outside.

HomerJSmith

Seems like a lot of work. What's wrong with water vapour escaping out of the vent or condensate running back to the boiler. I guess it could be dripping on the flower bed. I vent my exhaust on my mod con installations up 45deg and the put a 45deg fitting to horizontal at the end. I never use concentric venting.

Ya! Ultra vent! Great product until it had to be replaced. What about that other clear plastic vent piping or Entran, or Shell's wonderful gray plastic piping or Crown's plastic impeller induced draft motor or HTP's plastic impellers. I'm leery about the next Jasper coming down the Pike, telling me about the latest greatest thing that will save me money and time. I hate to tell you how long it took me to accept Pex. I'm still out on Propress and their o-ring seal.

JUGHNE

I think that the point where the exhaust left the building from the SS there may have been more than usual condensate produced, causing freeze up of the exhaust port.

IMO, I think that all ModCons should have a drip trip right at the exhaust of the boiler.
I have this crazy idea that the condensate washing back into the SS HXG adds to the "coffee grounds" issue and early corrosion of the SS.


I feel that that condensate is washing minor chloride's out of the hot/warm PVC and it ends up in the HXG of the boiler.

But what do I know?

Condensing FAF's have a drip trap on their exhaust piping that drains most of the condensate away before going back into the inducer exhausting fan.

True boilers have pressured heat exchangers and those fans never (should) see any water.