This expansion tank allows for the expansion of water when heated, thereby protecting closed-loop plumbing and heating systems from excessive pressure and leaks. It does this by providing a space for the water to expand into and absorbs pressure increases to prevent damage to pipes, water heaters, and other components.
 
We recommend these on any pressurised system. Recommended sizes below for your water tank:
 
Small - up to and including 10L tanks
Medium - Up to and including 15L tanks
Large - Up to and including 25L tanks