The LavaTap 1 inch male x female swivel anti freeze valve protects the outdoor pipework of a monobloc air source heat pump from frost without filling the system with glycol. Normally the heat pump guards itself against frost by running its pump. In a winter power cut, or if the unit locks out, nothing moves the water and the pipes outside can freeze and split. This valve needs no electricity: a thermostatic sensor in the water opens the drain when the water falls to 3°C, lets it run to waste until warmer water from inside the house reaches the valve, and closes again at 4°C.

Screws straight onto the heat pump: the 1 inch BSP female swivel nut fits 1 inch (G1) male flow and return ports, and the other end is a 1 inch BSP male thread for your pipework. A flat sealing gasket is supplied.

Specification: CW617N brass body, stainless steel springs and EPDM seals. Maximum pressure 10 bar. Water temperature 0 to 65°C, outdoor air -30 to 60°C. A vacuum breaker on top lets air in so the pipe drains freely, and an automatic shut-off means the sensor cartridge can be changed without draining the system. About 12.5 cm tall.

Fitting: one valve on the flow and one on the return, outdoors near the heat pump, upright with the drain pointing down, at least 15 cm above the ground and 10 cm apart. The supplied foam shell covers the valve body only: keep the vacuum breaker and the sensor cartridge uncovered. Keep the system pressurised and let the drain water run away. For water-only systems.

Will it fit? Verified 1 inch male connections include Mitsubishi Ecodan PUZ-WM, Samsung EHS Mono R290 and Daikin Altherma 3 M. Units with 1 1/4 inch connections, such as Vaillant aroTHERM plus, need the 1 1/4 inch version. For 28mm copper, choose the 28mm compression version.

Also sold as: KeyPlumb ZL-7201-1MF (1 inch male x female swivel anti freeze valve).

In the box: 1 x anti freeze valve with swivel nut, 1 x flat gasket, 1 x split foam insulation shell.