ESHIONG 1/4" Push to Connect One Way Check Valve for Reverse Osmosis Water Filter,NSF Certified Plastic Quick Connect RO Fittings (6 pcs)

Perfect for air gaps on reverse osmosis systems. If you don't know already, your drain lines for the dishwasher and reverse osmosis systems need an air gap or high loop to prevent sewage from entering those systems. These check valves fit the reverse osmosis drain lines perfectly and are a good second line of defense against sewage contamination. Just be sure to use them in conjunction with a high loop. One of the valves was a little noisy at first but quieted down after a little use. Overall, these are a good value, fit well, easy to install, and serve their purpose well.

I tried hooking one of these up backwards and my flow stopped. Hooking it in the correct way the water seems to flow the same as before. I call this a success. If it lasts over a year then great! If not then well that's what I get for buying cheap. I may re-review if I notice they stop working at some point. Side note: Not sure why people think they can supply enough pressure with wee little human lungs. Obviously the psi in a water hose is going to be higher than a set of lungs can push. If someone tries to say they cant blow through it and gives a bad review, ignore it and keep scrolling. If you're not supplying measurable data and saying its crap then do us all a favor and stay out of the reviews. Thanks.

Work well. Good buy. One way flow valve easy fit snug.

Couldn’t blow air through. Check valve not opening.

Beware that the cracking pressure is 7.25 psi, so this is meant for supply side pressure. It won't work as a check valve on the drain side. And of course trying to breathe through it won't be enough pressure to push through.