"This valve is used in older heating systems where an anti-convection flow check valve is fitted into the vertical pipework supplying upstairs radiators. The old valve [+/- 40 years old!] was blocked & even after I cleaned it it there was no hot water getting to the upstairs rads. The function of this valve is to prevent convection currents feeding hot water to upstairs rads when the circ pump is not running. Typically this will be in Summer when all that is required is convection circulation to the hot water cylinder coil to provide hot water for sinks, baths, & showers etc. Once the central heating circ pump is running the additional pressure is sufficient to open the check valve which is normally held closed by a light spring. My upstairs rads are now hotter than they have been in many years so I am well pleased with the simple piping mod to fix this valve in place."
"I used this product to stop the cold water from returning through the hot water supply in a bathroom with a mixer shower. The check valve lasted one week before it failed and I was called out urgently to rectify my installation, I have since used a double check valve and this seems to be doing the job.Not enough information supplied when buying the product i.e.pressure tolerance when connecting with mains supply."
"Failed within one week of being installed in a central heating system to stop a syphon circuit through the return pipe. I now have to drain the system again and replace it. Seriously unimpressed and now put to a lot of extra work."