2) Using a set of expansion controls
(Fig. 2 & 3).
If it is not possible to accommodate the expansion in the system pipe work,
it is then necessary to use a set of expansion controls. These comprise of
an expansion vessel and non-return valve (Kit A) and generally a pressure
reducing valve (Kit B). It is however possible to use Kit A without Kit B, but
the mains water pressure must never reach over 3.5 bar for the expansion
vessel to operate correctly. Therefore if the value of mains water pressure
cannot be guaranteed Kit B should be installed.