A step-by-step guide on descaling heat exchangers on Bosch tankless water heaters, for better performance and maximized efficiency. Find out who should perform descaling and detail instructions about the procedure and required tools.
The article about removing the limescale build-up covers most of the non-condensing and all condensing water heaters from Bosch and can be also implemented on other brands and models.
Descaling water heaters, especially tankless, is very important to keep the performance high and unit functional for many years. According to the manufacturers, flushing limescale should be done periodically, at least once a year.
The heat exchanger is a very important element on every tankless water heater, including Bosch, and it has to withstand high thermal and mechanical stress. Due to its design, which includes small water passageways, the heat exchanger is very sensitive to limescale and mineral build-up.
The scale build-up, if not properly removed, will not only reduce the flow rate, heater's efficiency or make the disturbing noise, but will shorten its life. This is especially important if you live in the area where the water supply has a high mineral content, also known as hard water.
A set of plumbing wrenches
Relieve the water pressure by opening hot water taps.
Use one of the three hoses and connect the inlet of the water heater and outlet of the pump.
Take the third cable and connect one end to the inlet of the pump and the other put in the bucket. This end will have a filter to reduce the larger particles to enter the system again.
Run the pump through the tankless unit and its heat exchanger. Depending on the amount of the lime build-up the returning solution might be unclean; it may take some time before it comes out clear.
Reconnect the hot water line and open all the water valves.