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Keeping pool water warm: Best practices to ensure long heater life

By Mike Fowler

The symptoms associated with heater failure can generally be narrowed down to issues with a burner or with the heat exchanger.
The symptoms associated with heater failure can generally be narrowed down to issues with a burner or with the heat exchanger.

Aquatic facility managers operating indoor pools this winter need to make sure the water remains nice and warm. Unfortunately, if the heater stops working, the pool water gets cold, very fast. There are, in fact, several best practices to follow to avoid the common causes of heater failure. Several tips and tricks developed in the field over many years should be included in any aquatic facility maintenance plan. From routine checks to keeping specific spare parts on hand, facility managers can keep heaters in tip-top shape and avoid having shivering bathers in the pool.


When it comes to looking at the common causes of pool heater failure, many are linked to improper installation. Therefore, aquatic facility managers preparing their pools for winter should take the time to review their heater’s installation.

Proper heater sizing

It is vital for the heater, along with other components in the equipment room, to be sized correctly for the facility’s pool along with any additional bodies of water that might be connected. This includes spas and splash play areas. To size the equipment properly, the specifications for the heater should be consulted to compare them to the flowrate that will be pumped through the unit.

To calculate an approximate heater size for a pool, technicians must do the following:

a) Determine the desired pool water temperature (average is 27.7 C [82 F] for competitive swimming).

b) Determine the average temperature for the coldest month the pool will be used (if it is an outdoor pool).

c) Subtract the average temperature for the coldest month from the desired pool water This will provide the temperature rise needed.

d) Calculate the pool surface area in square feet.

e) To determine the British thermal unit (Btu) output needed for gas pool heaters, the formula is calculated by multiplying the pool area (in square feet) by the temperature rise (ideal water temperature/average temperature in coldest month) by 12.

To clarify, heaters are sized based on a 24-hour temperature rise. Therefore, a heater with one million Btus takes 24 hours to raise the pool temperature 15 degrees for a 506-m2 (5450-sf) pool. Based on this information, the appropriate heater can be selected for the aquatic facility.

If the heater does not appear to be sized properly, it should be replaced. In fact, replacing older heaters with new, energy-efficient units will not only provide improved water heating but will also reduce energy consumption and lower operating costs in the process.

  • Make sure pool water chemistry is balanced at all times.
  • Make sure heater is venting properly.
  • Inspect burners and heat exchanger periodically for any sign of chemical damage or soot build-up.
  • Always make sure heater area is clear of debris, especially the area where the heater is venting.
  • Always ensure there is proper water flow going through the heater. S

One of the more common mistakes that occur when installing a new heater is upgrading the size of the unit without having a large enough gas supply.

A clear, blue flame indicates the unit is burning 100 per cent of the gas.

When considering requirements with respect to how far a heater can be vented, or how far ductwork can run to pull intake air, each 90-degree elbow reduces the maximum horizontal polyvinyl chloride (PVC) air intake run by 3.6 m (12 ft). Each 45-degree elbow reduces the maximum run by 1.8 m (6 ft).

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