In-Line Expansion Tanks

"How does the Watts ILT water heater expansion tank prevent bacteria and algae?"
The Watts ILT is designed to completely exchange all of the water in the tank upon flow. Unlike conventional tank designs that trap water, thus promoting the growth of bacteria or algae in the stagnant water, the ILT's flow-through design virtually eliminates pockets of water in the expansion tank that can accumulate when the supply pressure is higher than the tank's pre-charge pressure.

"Why install a water heater expansion tank?"
Thermal expansion occurs when water is heated during non-use (when all faucets are off) periods. The installation of a pressure regulator, or check valve, or a back flow prevention device (quite common in water systems) "closes" the water system. That means that there is no room for expansion in the water lines when heated. When water is heated in a closed vessel (such as a water heater) and there is no where for the pressure to go, it will increase the pressure in the water lines and water heater. That is not good for all of the piping and water heater as most are designed to take much more than 75 - 80 pounds of pressure as well as it can be dangerous. If the pressure reaches above the "breaking" point of your water heater the water heater could explode (if you do not have a temperature and pressure relief or one is installed but isn't working properly). Most local codes require an expansion tank that in a closed water heated system. Thermal expansion in a closed plumbing system can be damaging, dangerous and costly. Its effects include damage to water heater connections, gas water heater flue tubes, pumps serving washers and dishwashers, leaking faucets, "weeping" of water through the water heater Temperature and Pressure safety valve, and even noisy water hammering in the pipes (which can damage pipes). An properly sized water heater expansion tank (or chambers) eliminate these problems, by giving water a place to go ("expand to") when thermal expansion occurs.