Tanks and pressure vessels

Diaphragm tanks come in two kinds, and they are not interchangeable:

• pressure tanks — for cold water supply: they keep the pipes pressurised and save the pump from frequent starts;
• expansion vessels — for sealed heating and solar systems: they take up the water that expands as it heats.

A pressure tank diaphragm is made for drinking water and an expansion vessel diaphragm for hot heating fluid, so one cannot replace the other. Brackets and stands are in accessories; how to choose the volume is explained in “How to choose a pressure tank”.