Annual water heater maintenance: what to do yourself, what not to

Why maintenance matters at all

A water heater tank collects mineral scale on the heating element and loose sediment on the floor of the tank, both from the calcium and magnesium naturally present in Estonian tap water. Scale acts as insulation between the element and the water, so the heater draws the same electricity but heats less effectively, and eventually takes noticeably longer to bring a full tank up to temperature.

Left long enough, a thick layer of sediment traps heat against the steel at the bottom of the tank, which is where corrosion usually starts. A tank that fails from the inside rarely gives much warning beyond a slow drop in performance, then a leak.

None of this requires anything dramatic. A once-a-year routine, mostly things you can do yourself with the power switched off, keeps a heater running efficiently for its expected service life instead of shortening it.

Before the cold sets in: what to check in autumn

Autumn, before the heating season properly starts, is the sensible point in the year to look the heater over, since a fault found now is far less disruptive than one found in January with a burst pipe and frozen ground outside.

Switch the heater off at the breaker before touching anything. Check the pressure relief valve by lifting its test lever briefly; water should flow out and then stop cleanly. Look at the pipe connections and the drain valve at the bottom of the tank for any sign of weeping or corrosion, and check the insulation jacket or cupboard around the tank for damp.

• Test the pressure relief valve by lifting the lever for a few seconds
• Inspect pipe joints and the drain valve for corrosion or drips
• Check the thermostat setting is still reasonable, usually around 55–60 °C
• Look at the cable and plug or the fused connection for scorch marks or looseness
• Note the date of the last full flush, if you know it, and plan one if it has been over a year

Removing sediment from the bottom of the tank

Sediment settles at the base of the tank and is normally the easiest job on this list. Turn off the power and the cold water inlet, connect a hose to the drain valve, run the other end to a floor drain or outside, and open the valve. Letting a few litres run out and then briefly opening the cold inlet again to stir up the sediment, repeated two or three times, clears most of what has settled.

Do this once a year in an ordinary flat or house; if your water is particularly hard, twice a year keeps the tank noticeably quieter. A tank that has never been drained can produce grey or rust-coloured water and, occasionally, a jammed drain valve, which is a fair sign it has been neglected for longer than a year.

If descaling the element itself is needed rather than just draining sediment, that means removing the element, which is electrical work under load-bearing terminals and is where we would suggest calling a plumber rather than working past the point you're comfortable with.

The anode rod: what it does and when to replace it

Most steel-tanked water heaters have a magnesium or aluminium anode rod threaded into the top of the tank. It corrodes on purpose, sacrificially, so that the steel tank wall does not. Once the rod is mostly consumed, the tank itself starts corroding instead, which is not something that can be undone.

Checking it means switching off the power, closing the inlet valve, releasing pressure, and unscrewing the rod, usually from a hex head at the top of the tank. A rod that is thin, pitted down to the core wire, or coated thickly in calcium deposits should be replaced; as a rough guide, check after the first year and then roughly every one to two years after that, since local water hardness affects how fast it wears.

This is a job many confident DIYers manage, but the fitting can be seized after years without attention, and getting it wrong risks a leak at the tank's weakest point. If it won't move with reasonable force, that's the point to stop and call a plumber rather than force it.

What counts as electrical work, and when to call an electrician

Draining sediment and checking the anode rod, done with the power off at the breaker, are plumbing and mechanical tasks. Anything involving the heating element's wiring, the thermostat, or the fused connection to the mains is electrical work, and in a flat or house wired to normal standards that means a qualified electrician, not because the task looks difficult but because a mistake there is a fire and shock risk that a plumber's tools won't catch.

Signs that point to an electrical fault rather than scale or sediment include the breaker tripping repeatedly, a burning smell near the heater, visibly scorched terminals, or water heating unevenly despite a clean, descaled element. None of these should be worked around; they should be looked at before the heater is used again.

We do plumbing work on water heaters from 45 € per hour, and electrical work, done by a qualified electrician, from 49 € per hour. A call-out within Tallinn is 25 €, deducted from the bill if the work goes ahead.

The spring and summer once-over

Once the heating season ends, spring is a good time for a second, lighter check, partly because a summer without heating problems is easier to arrange repairs around than a winter emergency. Look again at the pressure relief valve and the connections, and if the heater has been running noisily or slowly all winter, this is the point to schedule the flush you may have put off in autumn.

Dry summer weeks, when nobody minds the water being off for an hour, are also the practical time to do a fuller descale or to have a plumber remove and clean the element if scale has built up beyond what draining sediment alone will fix. It's a straightforward job to book in July that becomes a much less convenient one in December.

Keeping to this rhythm, an autumn check, a sediment flush, an occasional anode inspection, and a spring look-over, is enough for most household water heaters and rarely takes more than an hour or two of your own time across the year.