Solar water heater not heating? Five things to check before calling a technician

Pune homes lose hot water from rooftop solar systems for a handful of common reasons. Many of them can be checked, and sometimes fixed, in 10 minutes — before you spend on a service call. Here is the short version.

1. Scale build-up in the tank After 2–3 years, hard water leaves a thick layer of calcium and magnesium scale inside the tank. This insulates the water from the heating tubes — the sun heats the tubes, the tubes try to heat the tank, but the scale stops the transfer. You feel "barely warm" water in the morning when it should be steaming.

Quick check: open the bottom drain valve briefly. If white or yellow flakes come out, you have scale. Tank descaling fixes this — typically every 2 to 3 years.

2. Broken or empty evacuated tubes Tubes can crack from hail, monkeys, falling branches or simple temperature shock. Even one missing tube means lost capacity. Empty tubes (where the inner glass has fogged or filled with water) are dead — they will not heat at all.

Quick check: go to the terrace mid-morning. All working tubes should feel uniformly hot near the top end. Cold tubes are dead and need replacement.

3. Stuck or scaled-up pressure-relief valve The PRV at the top of the tank is supposed to release excess pressure on hot days. When it scales up, water either leaks continuously (a small but constant drip) or builds dangerous pressure inside. Either way, the system underperforms.

Quick check: look for water dripping from the small pipe coming out of the tank top. If it's dripping when the tank is not being used, the valve needs cleaning or replacing.

4. Choked inlet/outlet pipes Hard water deposits build up inside the cold inlet pipe over years. Eventually water cannot flow in to be heated, or hot water cannot reach your tap.

Quick check: turn on the hot tap furthest from the tank. If the flow is much weaker than the cold side, you have a choke.

5. Controller, sensor or pump failure (pressurised systems) If you have a pressurised system with a circulation pump and digital controller, any of these can fail. The display will show error codes — refer to your manual or send us a photo of the screen.

When to call us: if all five checks come back okay and the water is still not heating, call us. Most service jobs take a single visit. We service all brands — Racold, V-Guard, Tata Power Solar, Anu Solar, Supreme, and others.

A general rule: solar water heaters last 12–15 years if serviced once a year. The annual service costs less than a single big repair, so an AMC pays for itself quickly. We offer one for both households and societies.