The price of non-return valves had led me to buy what it reminded me in retrospect again, the love of money is not always horny. Of the 10 valves I could discard a same because it was totally jammed. The other nine were working as far, but they were, as another reviewer has stated earlier, quite stiff. That is, must prevail a relatively high pressure in the forward direction, so that the gas passes through the valve. After several days in operation and the built valve was then completely blocked. It was clear to me that I can not really rely on the actually intended safety function. Especially since the CO2 hose is even plugged, which I did not really appear safe at the overpressure in the long run.
I have written down the purchase price as dues and I switched to a non-return valve made of metal, which requires only about 0.1 bar overpressure and additionally has hose fittings. That costs a ~ 10, but conveys a feeling of security and works flawlessly since about 2 weeks, which will hopefully remain so for a while ...
The main advantage of the selected non-return valve is that my biogas system now works only with a slight pressure and thus the risk of bursting of the reaction vessel, the rinse bottle or of a tube is much lower.
