1/8" NPT Male Service Check Valve

I've installed two of these and both have failed when removing the air vent. The application was on solar thermal systems, cold or return side. Perhaps the O-ring failed due to high temps. Took a good bath on both replacements of air vents because the check valve failed. I see there is a different model available now.

just what I needed

Works good and easy to install

This check valve is installed in the air expeller to limit water loss when replacing the air vent 'mushroom' that automatically vents air from the hydronic circuit (until the mushroom vent fails which in my case is about every 2-3 years. I've had to replace several fouled mushroom type vents in the past and that involved depressurizing the boiler circuit and removing the bad vent valve and threading in the new one. It's a simple task but there's still some hot water spilling and some air is introduced when the system is repressurized with fresh water. This service check valve prevents water loss and need for de/re-pressurization. The check valve closes when the vent valve is unscrewed and screwing in the new vent opens the check valve and allows the new vent to function. (There's a tang at the end of the male nipple on the mushroom that engages the check valve to open it when the threads are screwed into the check valve.) If I ran the universe I would have this inexpensive little service check valve installed in every hot water heating system.