Water Heater Condensation

What causes condensation in water heaters
How to reduce condensate in heating

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Water heater condensation is not a leaking problem. When the gas water heating appliance is working, condensate is the normal occurrence. How to recognize condensation in water heaters, what to do and how to troubleshoot it?

What is water heater condensation?

When natural or propane gas burns, there is a lot of moisture in products of combustion, and when the flue gas product - water vapor, is chilled below the dew point, water heater condensation occurs. The dew point is the temperature at which water vapor turns into the liquid state, called condensate.

When the main gas burner is on, the heater produces hot flue gases, which turn into the condensate upon contacting colder surfaces. One of the situations where the condensation might happen is piping cooled by the low incoming water temperature that flows through.

Why it condensates in water heaters?

In order to troubleshoot the water heater condensation you have to recognize the symptoms first and which part of the unit condensates.

Shortly after the start-up, when the gas heater is filled with cold water and the main burner is ON, the heater will release the condensate. One of the main symptoms of condensation is a puddle of water on the floor just below the unit.

Water heater condensation is happening, especially when dealing with the new heating appliances and for the first time.

You will also see a condensate after a long draw of hot water in a short time and when the refill water is very cold.

When the temperature setting is set too low, condensation might occur also. The solution is to increase the temperature.

An undersized heater is also the reason for more condensation, and even with a heater properly sized, you can expect some condensation. The heater should be properly sized to meet your family demand for hot water, for shower, dishwashing and cloth washing.

Problems and how to solve water heater condensation

Excessive water heater condensation is not normal, but it may be noticed during the winter and in early spring, when the outside temperatures are the lowest. This is what can cause the pilot light outage, premature corrosion of the burner area and the tank itself. Small black or red granules can be seen on the main burner and top of the heater.

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Hydrocarbons and carbonic acid are found in the condensate and they will corrode the heater. The most exposed parts to the condensation are flue tubes, baffles and burners.

Moisture from the combustion products will condense on the cooler tank and form water drops, which may drip onto the burner or any other hot surface, resulting in the characteristic sizzling, frying or popping noise within the burner area.

Continual exposure to the condensation will weaken the flue tube. It can also affect the gas combustion by producing a carbon monoxide.

Because of the suddenness and the amount of condensate, this problem might be diagnosed as the leaking. Keep in mind that one half of the gallon of condensate during every hour of operation is a typical for home heaters. It takes 1-2 hours for the tank to warm up so the condensation should disappear.

Since the new high efficient heaters and Energy Star models utilize the powerful gas burners; and combining it with the latest technology to extract even more heat from the flues and flames, they will condensate more than the older heaters that use less energy.

One of the solution when troubleshooting condensation in the heater is a good venting so the gas appliances will operate efficiently and vent the products of combustion together with the water vapor properly.

As the cooler flue gases are part of the reason for the condensation problem, suggestion is to raise the supply air temperature, increase the stored water temperature or increase the size of the tank.

A suitable metal drain pan, at least 2" wider than the heater should be installed under the heater to collect the condensate and not to damage the area.

How to distinguish between condensation and leaking

  • Make sure there is no water under the heater. If there is any wipe it off.

  • Turn the thermostat on the gas control valve to the pilot position.

  • Wait for a few hours or one day, to check is there any water accumulated under the unit.

  • When the heater is heated above 110 F, condensation should stop.

  • If there is no water under the heater, then you have condensation. If there is a puddle, check for leaking.

Condensing water heaters and condensate

Condensing water heater, Vertex from AO Smith, for example, requires a drain located close to the unit so condensate can drain safely. This heater has three places where the condensate drains from, bottom of the unit and where the blower assembly is installed.

Ensure that the condensate flow is free and clear of debris and the drain will not allow backflow through the hose. This is important, especially during the winter and freezing days.

On the power vent units, to prevent problems during water heater condensation, the vent pipe should always slope downward away from the blower. If this is not possible than an adequate water heater condensation trap or drain should be provided.