Start with the likely amount of hot water used at one time and the space available under the sink. Compare the draw-off and recovery information for each model rather than relying on capacity alone.
Under sink hot water units and immersion heaters
A small hot-water supply close to a sink can avoid long pipe runs from a central cylinder. MacBlair lists ATC under-sink water heaters in 5, 10 and 15 litre sizes, alongside internal and external immersion-heater elements. These are different products, so start by identifying whether the job needs a complete local unit or a replacement element.
The under-sink options differ in stored capacity. Check the available cabinet space, expected draw-off and the manufacturer's connection details before choosing a size. The tap it feeds also matters: compare the chosen unit with the kitchen tap options and existing pipe arrangement.
For an immersion replacement, match the element to the existing cylinder or heater by its specification rather than length alone. The broader hot-water cylinder range is relevant when the vessel itself needs changing. Check electrical and water connections against the manufacturer's instructions before installation.
Water Heaters FAQs
No. The under-sink products listed are complete small-capacity water-heater units, while an immersion element heats water inside a separate vessel. Choose the product type that matches the existing installation.
Check the heater instructions for the required tap arrangement, pressure and connections. Compare those requirements with the tap and pipework already fitted before ordering.
Record the existing element specification, including length, fitting and electrical rating, then compare it with the replacement product. If the original details are unclear, have the installation checked before purchasing.
The cupboard must have enough space for the unit and the clearances and connections specified by its manufacturer. Measure the usable space, including the route for pipes and wiring, not just the cabinet width.