Many instant hot water heaters require an anti-scalant system or the warranty is void. The Big Brand Water Filter anti-scalant systems costs less than the competitors.
This system is installed on the line feeding your instant hot system. It is important that the clear housing is not exposed to the hot water in your water heater. A one way check valve or other back flow device is recommended to prevent housing failure due to hot water.
Hot water heaters should always be equipped with pressure and temperature relief valves.