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Expansion Valve
Adjustable safety valve that bleeds excess pressure from the boiler back to the inlet, protecting plumbing from thermal expansion.
Category: Water System
A relief valve in the brew water line that opens to bleed pressure as cold water expands during heating. Prevents over-pressurisation of the brew boiler from thermal expansion.
Why it matters — Water expands by about 5% from cold to hot. Without an expansion valve, that expansion pressurises the sealed brew boiler and can cause leaks, blown seals, or stressed components.
Good to know
- Different from the OPV — the expansion valve handles thermal expansion; the OPV handles pump over-pressure.
- A constant slow drip from the discharge line, even when the machine is idle, often means the expansion valve is leaking and needs servicing.