In the UK, the use of a temperature relief valves or combined temperature and pressure relief valves is mandatory
for unvented hot water storage system in excess of 15 litres and also used on some vented hot water storage
systems. These valves can discharge at 96?C (BS EN 1490:2011). However, discharges from pressure-only relief
valves without temperature control will discharge at over 100?C.
self-sealing valve can be fitted to the discharge of unvented hot water storage systems, primary
thermal heat stores and heat interface units allowing them to be connected directly to sanitary pipework provided
they are fitted with a temperature relief valve or combined temperature and pressure relief valve.