Estimating the right capacity
A 50 litre heater is compact and reheats sooner, but may not cover two long consecutive showers. An 80 litre model often suits two or three people. A 100 litre unit provides more reserve but is heavier and slower to recover.
Also consider element power, insulation and whether several outlets are used together.
Wall strength and service access
A full cylinder weighs far more than the empty appliance. Concrete, solid brick and hollow partitions require different fixings; a weak wall may need reinforcement.
Leave access to the flange, element, anode, safety valve and isolating valves. A tightly boxed-in heater can be expensive to service.
Water connections and safety valve
Fit the safety valve on the cold inlet as specified by the manufacturer and provide a safe discharge route. Keep isolating valves accessible and assess ageing flexible hoses before installation.
Never energise the heater until the cylinder is full and water flows steadily from a hot tap. Excessive supply pressure may require investigation.
Electrical connection
Use a sound earthed circuit with suitable overcurrent and residual-current protection. The cable and outlet must match the appliance load and remain cool in operation.
Do not use an extension lead or travel adaptor as a permanent connection. Location and equipment rating matter in wet areas.
What to send before the visit
Send photographs of the wall, water points, nearest electrical supply and rating label. State the dimensions, capacity and whether an old unit must be removed.
Frequently asked questions
What size suits two people?
Usually 50–80 litres. If showers are taken consecutively or kitchen use is high, 80 litres provides a more comfortable reserve.
Can a 100 litre unit go on a partition?
Only after the wall construction and load capacity are checked. Reinforcement or a different position may be required.
Does it need a dedicated circuit?
A dedicated earthed circuit with correctly selected protection is the safest arrangement for a permanent high load.
Why does the safety valve drip?
A small discharge during heating can result from water expansion. Continuous heavy flow needs a pressure and valve check.