Meibes Prescor B Safety Relief Valve 1/2", 8 bar, Brass, Art. 27101

It starts to release water when the system pressure reaches 8 bar, after which the pressure stops rising; if the pressure climbs sharply, it opens fully. Before fitting it, make sure this set pressure suits your water heater and the rest of the installation.

For Prescor B valves the maker gives a system temperature range of 0 to 95 °C. The 140 °C figure is only a peak load, so do not treat it as a working temperature for the drinking-water system that the 8 bar valve protects.

No. The maker states that Prescor B has to be used in a closed drinking-water system, where it protects heated water against excessive pressure. Gas lines and central-heating circuits need valves designed for those uses.

According to the maker, venting by the valve can be prevented with a suitably sized expansion vessel for drinking-water systems. Without one, water expanding as it heats may push the pressure up to 8 bar and the valve will release water, so have the installer size the vessel.