Hot tub heater repair

A hot tub that won't heat usually has one of four problems: not enough water flowing through the heater, a failed safety switch or sensor, a burned-out element, or a control board that isn't switching the heater on. Before you book, check the filter, the water level and the set temperature, because low flow is the most common cause of all.

How the heater works

Most hot tubs heat with an electric element inside a stainless steel tube that the water flows through, mounted on or beside the control pack. The control board only switches the element on when its sensors say it's safe:

• Flow or pressure switch: confirms water is moving through the heater, so the element can't run dry.
• Temperature sensor: tells the board how warm the water is.
• High-limit sensor: cuts power if the water in the heater gets too hot.
• Heater relay: the switch on the board that sends power to the element.

If any of these fails, or reports a problem, the heater stays off. Depending on the control system you may see a code for low flow, overheating or a sensor fault, or simply a tub that slowly cools down.

Problems that look like heater faults

Plenty of "broken heaters" turn out to be flow problems:

• A clogged filter
• Water below the skimmer, so the pump draws air
• An airlock after a refill
• A closed valve in the equipment bay
• A weak circulation or jet pump

Each of these cuts the flow, so the pressure or flow switch keeps the heater off or the high-limit trips. Fix the flow and the heating comes back. Our guide to a hot tub not heating goes through the checks in order.

When the heater trips the GFCI

If the GFCI disconnect trips each time the heater comes on, the element is a common cause. As elements age, the metal sheath can crack and let current leak to ground, which is exactly what a GFCI is there to catch. Don't keep resetting it. Leave the tub off and book a repair. With the cover on, the water holds its heat for a while, but in freezing weather call us promptly: a tub with no power and no circulation can freeze in its pipes and pumps.

What a heater repair involves

With the power off, the work usually goes like this:

1. Check the flow through the heater: filter, pumps and valves
2. Test the element, including for a short to ground
3. Test the flow or pressure switch, the temperature sensor and the high-limit
4. Check that the board is sending power to the heater
5. Replace what has failed, then run the tub through a full heat cycle

A replacement element or heater assembly has to match the control pack, its voltage and its wattage, which is why we ask for the make and model when you book. Plug-and-play tubs on 120 volts have smaller heaters and heat more slowly than 240-volt tubs; that's normal, not a fault.

Scale and soft water

Where the water is hard, as in Aldergrove, scale can build up on the element and shorten its life. Very soft water, like the supply in most of Langley, Maple Ridge, Abbotsford and Mission, can be aggressive toward metal parts if calcium hardness is left too low. Balanced water protects the heater either way; see our water care guide.