Common Maintenance Items
What actually fails
Solar heating systems rarely fail at the collector. They fail at the fluid, the fittings, and the controls.
- Glycol: sample annually; check pH, freeze point, and color. Degraded glycol turns acidic, corrodes the loop, and can sludge. Replace every 5–10 years or whenever testing says so.
- Pressure: a slow pressure drop means a leak or a failed expansion tank. Check the tank's air precharge annually.
- Pumps and controllers: confirm the circulator runs and that ΔT setpoints still match the sensors; a drifted sensor runs the pump when it should not.
- Air vents and vacuum breakers: clogged vents cause noisy, stalled flow.
- Scale: hard-water direct systems need periodic descaling; an indirect loop avoids most of it.
- Collectors: clean glazing, check seals and mounting, clear snow, and look for condensation that signals a failed absorber or gasket.
- Tank: exercise the pressure relief valve, check the anode rod in potable tanks, and verify the tempering valve delivers no more than about 120 °F.
- Pool systems: cover, filter, and flow - a dirty filter starves the collectors of flow.
Worked example
At a five-year service the glycol sample reads pH 6.5 with a dark, cloudy appearance, and the loop holds only 12 psi where it was commissioned at 30 psi. Diagnosis: glycol has degraded and the system has lost fluid. Action: pressure-test, repair the leak, flush the loop, refill with fresh propylene glycol at the correct concentration, and check whether chronic stagnation overheated the fluid.
Traps
Topping up a glycol loop with water; ignoring pH because "it still looks pink"; skipping the expansion tank precharge; treating a tempering valve as set-and-forget.