On-demand or tankless water heaters require regular maintenance to operate efficiently and extend their service life. Unlike traditional storage-tank models, tankless units heat water only when needed, which makes them more energy-efficient. However, because water flows through narrow internal channels and directly over heating elements or heat exchangers, even small amounts of scale buildup can significantly reduce performance and cause overheating or system failure if not addressed.
One of the most important maintenance tasks for tankless water heaters is descaling or de-liming the heat exchanger. In areas with hard water, minerals like calcium and magnesium can quickly accumulate inside the heat exchanger, restricting water flow and reducing thermal transfer efficiency. Manufacturers typically recommend flushing the system with a vinegar or descaling solution every 6 to 12 months, depending on water hardness and usage. This involves connecting a pump and hoses to the service valves and circulating the solution for 45 minutes to an hour to break down and flush out scale deposits.
In addition to descaling, it’s essential to clean or replace the inlet water filter or screen regularly. This filter protects the internal components by trapping debris or sediment before it enters the heat exchanger. If clogged, it can reduce water pressure and trigger error codes. Checking the air intake filter (on gas models) and clearing any dust or obstructions is also necessary to maintain efficient combustion. For gas units, inspecting and cleaning the burner assembly and venting system annually helps ensure proper ignition, flame quality, and safe exhaust.
Routine visual inspections should also include checking for leaks, corrosion at fittings, and ensuring the electrical connections are secure. Error codes displayed on digital controllers should not be ignored—they can indicate flow rate issues, ignition problems, or scaling. Although some maintenance tasks can be handled by a knowledgeable homeowner, it is advisable to have the unit professionally serviced annually, particularly for gas models. A licensed technician can test gas pressure, inspect combustion efficiency, and verify that the unit meets safety standards.