Hot Tub Not Heating — Summer vs Winter Causes
Summer not-heating in the Tri-Cities is often deceptive. When ambient temperatures are 100°F and the spa sits in direct sun, the water may actually be at or above the set temperature without the heater running — which is correct spa behavior. If the spa display shows the water at or above the set point but you want it hotter, you're asking the heater to fight the ambient heat. Consider running the spa in the evening when ambient temperatures drop.
True summer not-heating — where the spa display shows water temperature well below the set point and the heater isn't running — is usually a high-limit sensor trip. The high-limit sensor shuts the heater off when it detects excessive temperature at the heater element itself. In summer, poor water circulation (dirty filter, clogged strainer) combined with high ambient temps causes the element surface to overheat and trip the high-limit even when water temp is normal. Clean the filter first.
Winter not-heating has different causes. The Tri-Cities doesn't get the extreme cold of Spokane or eastern Montana, but temperatures below 20°F occur most winters. At these temperatures, the heating element has to work continuously to maintain temperature in an uncovered or poorly-insulated spa. If the spa struggles to maintain temperature in winter, check cover condition first — a waterlogged or torn cover loses 70–80% of its insulating value and causes the heater to run constantly without achieving set temperature.
Hot Tub Overheating — A Tri-Cities Summer Problem
Hot tub overheating — spa shutting down with a high-temperature error — is significantly more common in the Tri-Cities than in cooler markets. The combination of direct sun on a dark spa cover, 110°F ambient air, and an equipment bay that can reach 140°F creates conditions where the spa water absorbs heat from the environment faster than the control system anticipates.
Most spa control systems have a maximum temperature limit of 104°F (mandated by UL standards). When water temperature reaches 106–108°F — which can happen in a Kennewick spa sitting in direct afternoon sun in July — the high-temperature protection trips and shuts the system down. This is the system working correctly.
Solutions: run a shade structure over the spa during peak afternoon hours (2–6pm) in summer, use a lighter-colored spa cover that reflects more solar radiation, or program the spa's filter cycles to run the pump (which promotes some cooling) during peak heat hours. If the spa is overheating despite these measures, check whether the thermostat sensor is reading accurately.
Calcium Scale and Heating Element Efficiency
Tri-Cities water at 150–220 PPM hardness deposits calcium carbonate on every surface it contacts — including the heating element. Scale on the element surface acts as an insulator, reducing heat transfer into the water and forcing the element to run hotter to achieve the same water temperature. Over time, scale buildup causes hot spots on the element that burn out the wire, causing total heating failure. Annual descaling and maintaining proper calcium hardness in the 150–250 PPM range extends element life significantly.
Service in the Tri-Cities
Desert Spa Repair services heating and temperature control issues across Kennewick, Richland, Pasco, West Richland, Benton City, and Finley. We carry heating elements, high-limit sensors, and temperature sensors for most common spa brands. Fixed quote after diagnosis, same-day available most days.