In most regions, the most popular way to warm a pool is with a gas heater. A gas heater’s flames heat water quickly and fairly efficiently. However, you may find that a solar heater (see Solar Swimming Pool Heaters) costs less to operate. Most commonly, a gas heater uses natural gas from the utility company. However, if there is no natural-gas pipe running to your house, the heater can be modified and fueled by propane via a propane tank on your property.
The most common type of gas heater is a coil heater, also called a flash heater. Here, the pool’s pump draws water through a filter and then through the heater where it travels through a heating coil located above the gas-fired flames of the unit’s combustion chamber. The flames heat the water as it passes through the coil.
For a small pool or a spa, the best option may be a convection heater, which has a single large flame that heats slow-moving water in a large tube. In other instances, a tank heater may be best. This operates like a standard home hot water heater, keeping a tankful of water hot and ready to be supplied to the spa.
As is the case with home water heaters, newer models are often much more energy efficient. A heater rated at 90 percent efficiency will save you a good deal over the long haul over an older model, which may only operate at 60 to 70 percent efficiency. Newer models have pilotless ignitions, meaning that a spark ignites the flames when the control calls for heat. In older models, the pilot light runs constantly, which wastes gas.
Have a gas heater inspected and cleaned by a heating pro at the beginning of each season. Adjusting the flames and cleaning the ports annually will make the unit run more efficiently.