Choosing a water heater
How to choose a storage water heater for a flat
Tank volume decides how many people can shower in a row; power decides how quickly the water reheats.
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The short answer
For one or two people and a shower 50 l is usually enough; for a family of three or four choose 80 l. All WetAir models have a 1500 W wet element and a magnesium anode; MWH1 adjusts the temperature in 1 °C steps, MWH4 has five fixed settings from 35 to 75 °C. Check the dimensions against the wall space before buying: 715 mm high for 50 l and 1030 mm for 80 l.
How many litres you need
Estimate how many showers are taken in a row in the morning or evening. A 50 l tank suits one or two users and a kitchen, 80 l a family or filling a bath. A larger tank takes longer to heat from cold but makes you wait less often.
Power and heating time
The 1500 W element is the same in both series, so an 80 l tank heats up longer than a 50 l one roughly in proportion to its volume. ECO mode holds 55 °C, which is enough for a shower; heating to 75 °C is rarely needed.
Controls: MWH1 versus MWH4
MWH1 has a digital panel with 1 °C steps; the chosen value is stored after 5 seconds, the maximum is 75 °C and indicators show heating and readiness. MWH4 offers five fixed settings: 35, 45, 55, 65 and 75 °C — simpler, without fine adjustment.
Tank protection: wet element and magnesium anode
A wet element is in contact with the water and heats it directly. The magnesium anode protects the steel tank from corrosion by being consumed instead of it, so its condition is checked during scheduled servicing — the manual sets the interval.
Dimensions and installation
All models are 385 mm wide; depth is 385 mm, or 340 mm on MWH4-50L; height is 715 mm for the 50 l units and 1030 mm for the 80 l units. Leave installation and connection to a qualified fitter and follow the manual.
Pre-purchase checklist
- Count how many people use hot water in a row.
- Measure the wall space allowing for the 715 or 1030 mm height and the pipework.
- Choose the control style: 1 °C steps on MWH1 or five fixed settings on MWH4.
- Check that the wall can carry the weight of a full tank.
- Plan professional installation and access for servicing.
Common mistakes
- Choosing 50 l for a family of four and waiting for hot water every morning.
- Keeping 75 °C permanently instead of ECO 55 °C.
- Installing the heater yourself without checking the wall and the connections.
- Never checking the magnesium anode for years.
Models to compare
WetAir manuals and support
Check the exact model requirements
For installation, anode replacement or diagnostics contact a qualified fitter or WetAir service; do not dismantle the unit yourself.
Sources and verification
Volume, power, temperature modes and dimensions come from the WetAir MWH1 and MWH4 manuals (dimensions page). The user-count advice is guidance, not a guarantee.
Frequently asked questions
50 or 80 litres?
One or two people — 50 l; three or four, or filling a bath — 80 l. Note that the 80 l tank is 315 mm taller.
What does ECO mode do?
ECO holds 55 °C: less energy to maintain the temperature and less scale than at 75 °C, and it is enough for a shower.
Why a magnesium anode?
It protects the steel tank from corrosion by corroding instead of it, so it is checked and replaced periodically.