Gas Water Heater Condensation

by Jim
(Chelsea Michigan)

I have an 8 year old gas hot water heater with a power vent and a condensate drain portal at the base of the vent pipe. The unit has worked fine with no condensate for all 8 years. We took a week's vacation. Before we left, I turned off the water pressure to the house. I always do this, as a precaution in case a toilet supply line, dishwasher or washer hose were to burst while gone. No water was consumed while we were gone.

I turned the house water back on when we returned. All seemed fine with everything. The day after we got back, I noticed that the condensate drain line creates and drains a large amount of water whenever the hot water heater fires. It drains condensate continually until the heater stops firing. It drains as much as a gallon in about 20 minutes.

The water heater seems to function normally in all other respects.
What is causing all the condensation? I need to run it to a floor drain with a length of tubing. I never had any condensation before.

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Oct 04, 2011
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starstarstarstarstar 		The cause of water heater condensation
by: Zee from water heater reviews

According to the manufacturers there are three main reasons why gas water heater will condensate:

- When a new water heater is filed with cold water for the first time.

- Undersized heater.

- Temperature setting is too low.

- Cold supply of the air might cause the flue gases cool below the "dew point", or when the condensation becomes visible.

- Large amount of hot water is used in a short time while the incoming water is very cold. Keep in mind that the cold incoming water during the winter time and periods of cold days might produce large amounts of condensate.

- Condensation increases if the unit is more efficient, when the temperature of the flue gases is lower.


I am guessing that after your vacation and after water heater was running for a few hours, condensation stopped.

Flue gases contains a large amount of moisture which usually condense on the cooler tank. This is why it is essential to provide a proper unobstructed venting so all the moisture can leave the heater.

I hope this explanation will help you find the answer and possible solution for your "problem" with the condensation.


What causes condensation in the heaters? How to reduce condensate in heating.

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