How to Deal with Condensation in Venting on Power Vent Water Heaters

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Learn how condensation in venting is generated, what causes it, how it affects your gas water heater, and what to do to avoid or fix it.

Condensation, due to its acidic characteristics, is something to avoid in power vent water heaters, and most of the time, is the result of a piping configuration and environmental conditions.

Most typical installations of gas water heater do not require any special methods for condensate disposal. This includes installations in the basements, garage, inside the home, and piping through the wall, attic, and where the pipes are short.

We will explore two scenarios of how venting pipes are installed; horizontal vent installation through the outside wall and vertical through the roof.

Horizontal venting

In horizontal vent systems, the vent pipe can slope away or toward the water heater. If the vent pipe slopes away, the drain port cap located where the pipe exits the water heater (blower pipe coupling) should stay in place, and the slope has to have at least 1/8 inch per foot. This is the recommended setup, but if it cannot be achieved, then the vent pipe will slope toward the water heater, so condensate collection and disposal must be provided. This is how:

Locate the blower pipe coupling at the top of the heater and remove the drain port cap.

Connect one end of the flexible tube to the blower drain port. The tube should be long enough to provide proper drainage, has the correct inner diameter (usually ½”), and is made of silicone for flexibility. 

Make the circular trap (P shape loop) about 12” below the top of the unit and secure it with the zip ties to prevent the loop from unfolding. The loop must be smooth, with no restrictions or kinks; it must provide free condensate drainage.

The loop must be filled with water to prevent combustion gases leaks into the room.

Direct the other end of the silicone drain tube to the floor drain or outside the house.

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Vertical venting

In the case of the vertical venting, take the same action steps as in the previous scenario, with the unplugged drain port and proper drainage via a silicone tube. Keep in mind that all horizontal sections must slope toward the water heater at 1/8” per foot.