How to install a water heater under the sink

modified: July 26, 2023

Learn how to install an electric water heater under the sink in this dedicated guide. Procedures and tips for correct installation.

Fitting an electric undersink water heater


An electric undersink water heater is a practical and efficient solution for reducing clutter as it allows you to optimise the position of your boiler. It is obviously important to purchase a device compatible with this type of assembly that is already configured to allow the system to be fixed properly. Attention must also be paid to the presence of water in the system as the resistor must remain under water at all times. Here’s everything you need to know about installing an electric undersink water heater, remembering that this is something that should only be performed by qualified technicians.

What is an electric undersink water heater?


A water heater is usually mounted on the wall above a sink, with the water inlet and outlet pipes at the bottom. In undersink models, this configuration is reversed: the ducts for the water inlet and outlet are located at the top of the water heater. The resistor is also in a different position in electric undersink water heaters so that it remains underwater and there is no risk of it burning out.

How to mount an electric undersink water heater


Before installing the water heater under your sink, we recommend buying a new high-energy efficiency device to ensure low consumption and savings on your electricity bill. The best option to simplify the assembly of a new boiler is to choose a similar model with the same dimensions as the old system and the same measurements for the pipe connections. It is also advisable to discuss the purchase with a specialist technician to understand if it is suitable for your sink or if alterations need to be made before assembly. The professional will then proceed with disassembling your old water heater, if it is a replacement, or will immediately begin mounting the new system. The support brackets should be mounted to properly lock it in place, carefully measuring the position of the electric water heater under the sink, taking into account the water pipes and leaving enough space for maintenance. The technician will then mount the water heater, connect up the plumbing, respecting the inlet and outlet of the water and assembling the safety group. Finally, they will connect up the electricity and test the system, a delicate phase that must be carried out carefully so as not to risk burning out the resistor, making sure the tank fills up and there are no leaks. If everything is in order, the professional will purge the air from the pipes, switch on the water heater and check that the system is in perfect working order.

The benefits of installing an electric undersink water heater


As we've seen, electric water heaters are usually installed above a sink, although it is possible to mount them under the sink in some situations. For example, there may not be enough space in the house for a larger product, so smaller water heaters can be placed under the sink. Alternatively, they may also be suitable for very large houses, where a single boiler may not be able to provide domestic hot water to every room. In this case, it is possible to integrate the system with a small electric water heater, perhaps under the sink, to be installed in a kitchen or bathroom. In addition, these devices allow you to optimise energy consumption, as the water heater is mounted near the sink, an option that reduces heat loss and decreases the time required to get hot water from the tap. The aesthetic aspect is also important, as an undersink water heater can be hidden from view in the cabinet under the sink.

Mounting an electric undersink water heater: who to contact


The installation of an electric undersink water heater is an operation that requires expertise. Compared to mounting a traditional boiler, it is important to carefully consider the overall dimensions and connections. For this reason, it is essential to always contact a professional, an experienced technician who can help you choose the most suitable model, check that it is compatible with being assembled under a sink and install it properly.