How often does an electric water heater need servicing?

The short answer

The one job that matters most on an electric water heater is the magnesium anode, a sacrificial rod that corrodes so the steel tank does not. Most manufacturers we checked say to have it inspected or replaced every two years: Nobel, De Dietrich, Ferroli and Bosch (standard water) do. Bosch says every year where the water is hard, from 20°fH. Several brands go further and make the anode work a condition of the tank warranty, so skipping it can cost you the cover, not only the tank.

The anode, brand by brand

What the documents we read actually say:

• Ariston (Greece): the warranties are valid only with a mandatory magnesium anode

replacement by certified personnel within 2 years of purchase, and the replacement must be certified by the authorised service centre. The anode itself is not covered by the warranty.

• Bosch: for the warranty to apply, the anode must be working. Bosch says it should

be checked every two years by its official service and renewed when needed, every year in areas with critical water (CaCO3 above 200 mg/L, from 20°fH). A tank without a properly working anode is not covered. This is Bosch's Spanish warranty document, so check what applies to your market.

• Ferroli (smart electric water heater manual): "the warranty is only valid if the

anode is replaced every two years."

• Nobel: its technical manual says to check the anode every two years and replace it

if required, with power off and the appliance drained. Damage from anode wear is not covered by the warranty.

• De Dietrich: the owner's instructions list an anode check every two years, to be

done by a professional, for models with immersion elements or steatite elements.

• Tesy: its warranty card ties the longer tank warranty to an inspection and anode

replacement by an authorised Tesy partner between the 25th and 27th month after purchase. Without it, the shorter two-year warranty applies.

• Gorenje: for pressure tanks the 5-year tank warranty requires one anode wear

inspection within 36 months of registering the warranty. For the 7-year range, that inspection must repeat every 36 months. This is from Gorenje's Croatian warranty page.

Note the spread: two years is common, but Gorenje allows three and Bosch asks for one in hard water. Use your own manual's number.

Descaling and the safety valve

• Descaling: De Dietrich says to descale every two years in hard-water regions, to be

done by a professional, and not to scrape the inside of the heater. We found no descaling interval in the other documents, so we do not give one.

• Safety valve: Nobel's manual says to check it at regular intervals, every six

months, to make sure it works. Ariston's warranty also requires a genuine safety valve correctly installed.

Keep the paperwork

Because the anode can decide a warranty claim, keep the dated service report and the purchase invoice together. Ariston and Tesy both say the replacement must be done or certified by an authorised service, so a DIY swap may not count.

Is it a legal requirement?

We did not find a legal deadline for servicing an electric water heater, and did not search for one. Treat the two-year anode interval as a manufacturer condition tied to your warranty.

Before you rely on this

These are the documents for the models in the sources above; other ranges from the same brands can differ, and the Bosch and Gorenje documents come from other countries. Your own manual and installer have the final say.

Track it in Epimeleia

Add the water heater as an item, record the purchase date, and set a reminder for the anode inspection two years on, or earlier if your brand names a window, as Tesy's 25 to 27 months. Attach the service report so you can show it if a tank warranty claim comes up.