Tag: Trap

This is a recent call I ran that clearly had an interesting past. It had a condensate pump to pump the water just a few feet up to a drain that went to a common drain. The “cleanout” after the trap is supposed to be a vent, not a cleanout, which means it needs to be uncapped and vented higher than the indoor drain pan so that if the drain backs up the water goes back into the system and trips the condensate switch.  With the current position, the vent could not be raised because it would come right up in front of the filter.

My best guess is that when the installing contractor installed a new, larger air handler it no longer had the fall they needed to get the existing drain so they capped the vent (seen in the photo above before it goes into the wall).

I’m using this system as an example because it has every possible drain don’t you could come up with

  • No Cleanout
  • No float switch (condensate switch) to prevent pan overflow
  • Vent Improperly placed or causing filter obstruction
  • Using a pump when one wasn’t originally needed
  • Using a common drain with no vent
  • No insulation on the condensate drain horizontal runs

We did rectify as much of it as we could here which included

  • Adding a condensate switch
  • Repiping with a proper cleanout and vent before the pump
  • Insulating the horizontal portions

Unfortunately, we couldn’t eliminate the pump and I forgot to take “after” photos

This is an example of a drain properly pitched, insulated, trapped and vented with a system and secondary pan switch installed. Two things I do notice on this one is the pan doesn’t look like it overlaps 3″ at the top of the unit, The cleanout would be better right above the trap and I can’t tell what’s supporting this drain to ensure the pitch stays correct.

It’s amazing how much there is to the simple, humble condensate drain.

— Bryan

Condensate_Pump

One of my techs (Jim Walch) mentioned to me that another common “double trap” style issue that comes up often is techs and installers running a drain too far into a condensate pump.

When you run the system drain too deep into the pump reservoir the water level can rise high enough to cover the drain end. This can create the same type of “airlock” you get with a double trap.

When draining into a condensate pump only extend the drain tube 1″ or so into the reservoir of the pump to prevent the water from rising and covering the end. Also, make sure to wire up the overflow switch on the pump in series with your system condensate switch so that whether the pump itself fails or the system drain pan has a blockage it will shut the system off.

Simple stuff, but it can prevent thousands of dollars in damage.

— Bryan

Double_trap

Double traps are no good. End of tip. Ok, here is some detail.

Anytime your drain goes up and down more than once you have a double trap UNLESS you place an air vent between the two traps that vents ABOVE the drain inlet.

The double trap causes drainage issues because air becomes trapped between the two traps and air is lighter than water. This causes the air to want to travel up as the water flows down resulting in NO DRAINAGE.

A vent allows the air to move instead of becoming trapped. This is why you vent a drain after the first trap if there is another trap or the potential of another trap.

This is also why you vent a drain after the first trap and before a common drain if you are connecting more than one drain. It helps prevent the possibility of a double trap and thus prevents a nasty backup.

In general just pitch the drain properly, install only one trap and don’t interconnect (unless required) and you will have no problem.

That was easy!

— Bryan

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