Water Heater Condensation

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How to fix or reduce water heater condensation. Condensation is usually considered as the leak... find out the reasons and symptoms for the worry-free heating.

One of the questions I've got from my readers is about water heater condensation. Users were complaining about the puddle of water under the gas-powered heater - after coming back from a vacation, during the winter time, or once they purchased a brand-new unit.


The puddle of water around the heater is the first sign of the water heater condensation or leak. You might also find black or red granules on the main gas burner, when the condensate was dripping on the hot surface (you will also hear a sizzling noise). Corrosion on the jacket or around the vent is also a sign that the condensate (moisture) was present there.

Condensation - cause and potential problems

When natural gas or propane gas is burning inside the combustion chamber of your gas heater, the flue gases are released. They contain lots of moisture and when it is chilled below the "dew point", the condensate forms. The "dew point" is the temperature when the water vapor turns into liquid.

The heater will usually produce one half gallon of moisture every hour of heater's operation, so the condensation is the normal occurrence.

Today's heaters are producing even more condensate due to their high efficient operation - condensation usually noticeable when the efficiency is above 87.5%. High efficient heaters, including condensing heaters are utilizing flue gases' temperature to transfer even more heat to water, which is reducing the temperature of the flue gases so the water vapor turns into liquid - condensate.

It is very simple to identify is there a condensation or not. If there is some water under the heater, wipe it up. Turn the gas control valve to OFF position. Wait several hours to see is it wet under the heater. No water means the heater was condensing.

There are several reasons why water heater condensation occurs:

  • Flue gases are cooled below their "dew point" when having the cold air supply.
  • When the temperature of water inside the tank drops below 110 F. Once the water inside the tank is heated above 115 F condensation should stop. It takes up to 2 hours for water to heat up to the temperature where the condensation stops.
  • During the cold start-up of the brand-new unit.
  • An undersized gas heater.
  • Temperature setting is too low.
  • 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.
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If you have one of the above situations that will form the condensation, fix the problem by increasing the temperature of the incoming air, water or tank size. Proper, unobstructed venting is also important so the moisture can leave the heater easily. As the condensate is mild acidic, and will corrode steel, PVC and stainless steel vents are recommended, if applicable and per code.

The problems associated with the water heater condensation are the following:

  • The condensate can drip onto the burner causing the pilot outage.
  • Corrosion on the metal surfaces.
  • Puddle of water.

PowerVent and Power Direct Vent heaters are equipped with the condensate drain so the water vapor from the exhaust gases will roll down the PVC vent pipe and through the drain port out. Recommendation is to get a condensate drain kit for convenient draining, and metal drain pans to protect the room where the heater is installed.

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