Solar water heater on the roof: drips, lukewarm water and when it needs servicing

Quick answer first: a solar water heater that lets out a short drip from its relief pipe on a blazing afternoon is doing exactly what it was designed to do. A trickle that runs all day, or a brown stain spreading on the ceiling under the tank, is not — that needs attention before the ceiling does. And if your showers have gone merely lukewarm, the fault is usually not the panels at all: it is the electric backup element inside the tank, which is an electrical job, not a reason to replace the whole system.

The drip that is normal

Every solar tank has a temperature-and-pressure relief valve. Around midday on a hot Serdang afternoon, the water in the tank hits its peak temperature, expands, and the valve releases a little of it — a short hiss and a few cupfuls down the relief pipe, usually between noon and 3pm, stopping by evening. We have been called to “leaking” heaters that were doing nothing more than this. If the drip appears only on hot afternoons and the pipe is dry in the morning, save your money.

The leaks that are not

• A steady trickle from the relief pipe, even at 8am. The valve seat is scaled up or stuck open — common in Klang Valley water — or the backup thermostat is overcooking the tank. Either way the valve or thermostat needs replacing, not ignoring: you are paying to heat water that runs straight onto the roof.
• A ceiling stain below the tank. Check where it sits. Water from a leaking tank joint travels along rafters and pipe runs before it drops, so the stain is often half a metre or more away from the leak itself. A stain that grows after sunny days (not rainy ones) points at the heater, not the roof tiles.
• Cracked lagging and chalky white pipes. UV eats the foam insulation and makes exposed uPVC brittle. Perished lagging also means the system loses heat all night — often the real reason morning showers got cooler.

Lukewarm water? Suspect the element, not the panels

Solar panels fail slowly and rarely; backup elements fail often. The giveaway: if water stays lukewarm even after two or three cloudy days when the backup should be carrying the load — or the heater’s breaker or ELCB trips when you switch it on — the element or its thermostat has gone. This is live wiring inside a water tank, so it is firmly not a DIY job: all electrical work on heaters is carried out with our licensed partner contractor, Suruhanjaya Tenaga compliant, typically in the RM 80–600 range.

The servicing nobody does

Two small jobs decide whether these tanks last 8 years or 20, and almost nobody does them:

1. Sediment flush, yearly. Opening the drain valve until the water runs clear clears the mineral sludge that buries the element and slows heating.
2. Sacrificial anode, about every 5 years. A cheap magnesium rod inside the tank corrodes so the tank itself does not. Once it is gone, the tank starts rusting from the inside — by the time the water runs brown, it is usually too late. In twenty-odd tanks we have looked at, we can count on one hand the anodes that had ever been changed.

One firm warning about the roof

Everything above happens two storeys up on clay tiles that crack underfoot and grow moss in the rainy season. Checking the relief valve is not worth a fall — this is a job for proper boards and two people, and it is where we draw the DIY line. What you can do from the ground: watch when the drip happens, note where the stain is, and check whether the heater breaker trips. That information alone makes the eventual visit faster and cheaper. Our price guide shows the ranges, and the services page covers what a service visit includes.