Brass In-Line Spring Check Valve

Flow entering the inlet pushes a poppet off its seat against a light spring. When the flow falls away the spring returns the poppet before reverse flow can build, so closure is driven by the spring rather than by gravity or by the reversing column. That is what distinguishes this pattern from a swing check: it seals in any orientation, and it closes quickly enough to limit slam when a pump trips.

The valve photographed is a brass body, female threaded at both ends, with the poppet visible through the inlet. No manufacturer name, pressure class, thread form or temperature limit is marked on it, so those are order variables rather than published figures and none of them is asserted here.

Typical duties are pump and booster-set outlets, water risers, small compressed-air lines and light oil service. State the nominal size, the thread form (BSP parallel, BSP taper or NPT — these are not interchangeable) and the working pressure and temperature the line will see. Where the valve is going into a drinking-water installation, single check valves of this pattern fall under EN 13959, anti-pollution check valves DN 6 to DN 250, family E types A to D; ask for the maker's declaration if the specification calls for it.