Flushing tankless water heaters – a simple step-by-step guide. Don't guess; find out when and how to flush your tankless heater. If you want to maintain the top performance, efficient heating, and long life of your tankless unit, simple cleaning and flushing out the limescale and sediment buildup is the way to go.
Tankless water heaters, as opposed to tank-type heaters, do not store hot water. The cold water runs through the heat exchanger, where it is heated by the gas burner, usually located underneath. The heat exchanger utilizes a set of water pipes supported by a number of thin fins to enhance the heat transfer.
As the tankless heater can be affected by water quality, every manufacturer of tankless water heaters recommends regular cleaning and maintenance, where flushing is the most thorough. As hard water is found in many households, primarily if the well water is used, the heater might develop limescale and mineral deposits on the heater's elements.
Sediment build-up is mainly an issue when water is flowing through the narrow water passages of the heat exchanger, as it might clog the element, prevent regular heating operation, and other problems. Mineral buildup can even produce hot spots and corrosion, which will wear down the combustion chamber walls, affecting the lifespan of the unit.
As it can be seen, the most important element in tankless heaters is the heat exchanger. Flushing tankless water heaters whose heat exchangers are blocked by the limescale is crucial and must be done when suggested or as soon as the problem is detected. If not, the problem will aggravate.
Most modern water heaters are equipped with sensors and a diagnostic system that reacts and notifies the user when the limescale develops. In the case of Rinnai, on the remote controller or display, you can see "LC" or "OO" error codes, which indicates that there is a problem that indicates that flushing is required.
If you don't flush the water heater, the heat exchanger can damage due to high temperatures, as the insufficient flow of water will pass through and won't cool the element down.
Note: Keep in mind that the warranty does not cover any damage related to limescale buildup.
As said, flushing a tankless water heater is not complicated, and once done correctly, you have to reset the fault code by resetting the power. Here are the step-by-step instructions (I will consider that isolation or service valves are installed):
The Rinnai manufacturer recommends the instruction as described in the above text. This is a safe and effective way of flushing tankless water heaters, which its owners or a professional plumber can do.
You can also buy a flush kit, which generally includes a pump, hoses, hose adapters, a bucket, and descaler as an option. The kits are compatible with tankless valves and can be easily connected.
Manufacturers of the tankless water heaters recommend flushing the mineral deposits at least once a year, or more often if you leave in an area with hard water.