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 the number of thin fins to enhance the heat transfer.
As the tankless heater can be affected by the quality of water, every manufacturer of tankless water heaters recommends regular cleaning and maintenance, where flushing is the most thorough. As the hard water is found in many households, primarily if the well water is used, the heater might develop limescale and mineral deposits on 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 normal heating operation and other problems. Mineral build up can even produce hot spots and corrosion, which will wear down the walls of the combustion chamber, 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 the sensors and diagnostic system which reacts and notifies the user when the limescale develops. In a case of Rinnai, on the remote controller or display, you can see "LC" or "OO" error codes, which indicates that there is a problem which 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 build-up.
As said, flushing a tankless water heater is not complicate, 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 instruction from the above is recommended by the Rinnai manufacturer. This is a safe and effective way of flushing tankless water heaters, which can be done by its owners or a professional plumber.
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.