How to Install a Spa Heater
image by A. Johnson
There are two common types of spa heaters: an electric heater found primarily in portable above-ground spas and a gas heater found mostly in in-ground spas. The gas heater can use either natural gas or propane. The purpose of the heater is to heat and maintain a constant set temperature of the water in the spa; much like the heater in a home heats and maintains the air temperature of the home. The control mechanism is a thermostat that will require a power supply, usually 110 volts.
Locate where the heater is to be installed. Both types of heaters are installed on the discharge side of the pump. The pump pulls the water out of the spa through the filter and heater and back into the spa.
Plan to install the gas heater in the area where the other equipment is located, which is usually a safe distance away from the spa and close to the electric and gas supply. The other equipment consists of a motor and pump assembly, and a filter, and sits on a concrete slab or other foundation and in some cases, behind a privacy screen or fence.
Locate the water line coming out of the filter and install the heating unit, which is a square box with a gas fitting and a power hookup for the switches and thermostat. The heating takes place as a burner is ignited and heats a manifold as the water passes through it.
Attach the inlet and outlet water pipes to the heating unit. The installation can be plastic (PVC) pipe, which would require the use of couplings that use glue for connecting, and unions for easy removal if necessary. The unions are threaded, so a pipe wrench for a 2" to 3" pipe is required. The pipe is attached to the heater with a flange fitting bolted onto a flange on the heating unit. A crescent wrench or box wrench is needed.
Connect the electric power supply for the controls box on the heater with the use of wire nuts.
Connect the gas line from the gas supply to the gas fitting on the heater using a crescent wrench. Install a gas valve to turn the gas off and on when necessary. Use pipe thread sealer on all fittings.
Install an electric heater in much the same way. This type of heater is an element inside housing and is mounted in line on the discharge side of the pump, usually inside of the spa cabinet. The piping is usually plastic (PVC), and the use of union type fittings should be used for ease of removal if necessary. The element heats the water as it passes through the piping.
Install the electric power supply to the heating unit, making sure the power is turned off prior to installation.
Check all fittings for leaks and tighten if necessary. Check the gas fitting on the gas heater for leaks with a spray bottle filled with soapy water.