John Guest3/8" One Way Check Valve RO Reverse Osmosis Water Filter NSF Certified

I just replaced our now 15 year old kitchen sink. I wanted something new and more modern looking than the builder installed Ivory colored double bowl. I went with a large single bowl stainless steel sink. I added two soap dispensers and a brand new stainless steel faucet for our Reverse Osmosis water filter. I pretty much had three initial goals in mind for this project. (turned into 4).What I wanted..1. Simply the plumbing under the sink (currently it's really jam packed down there).2. Combine the RO filter's waste water with the dishwasher exhaust.3. Eliminate that annoying gurgling sound that an air gap faucet makes.4. Install a nicer RO faucet.So going with a single bowl sink definitely makes a world of difference. Because there is no divider the usable sink space is massive. Underneath the fact that you only have one drain also simplifies connections. I used a  Watts Premier 164020 DLA-D Drain Line Plumbing Adapter  to allow me to connect my dishwashers output to the unused side input on my Waste King disposal unit. I used this back-flow preventer to eliminate any possibility that dirty water coming from the dishwasher or the compactor can work it's way back into the reverse Osmosis unit.I will point out that in some areas an air gap is required (by code). I personally do not really care about that. In my situation the RO filters waste water enters the disposal at a very high point and drains a good 10 plus inches before the trap so there is more than enough room there to eliminate any problems. This device in reality is just insurance and at $10 it's cheap insurance.The reasons for doing what I did were numerous. First There is a much wider range of styles of non air gap faucets available out there, I was able to find a really nice stainless steel unit that matched my main faucet. Secondly by choosing a non air gap faucet you totally eliminate any noise that the air gap produces, basically the RO filter becomes a totally silent appliance.All in all this was a great purchase. It works great, it's simple to install and it was cheap.I hope that this review is helpful. If you have a question or concern please feel free to post it and I will try to answer you within 24 hours.

I use this to replace the valve on my water aeration system. The check valve is fine and it does not leak however when the system is running and it's sucking air through it and makes an annoying vibrating noise that the old one didn't make but at least it doesn't leak

Delivery was a day later than originally expected. Product works fine. Installed to convert an air gap reverse osmosis water filtration system to non air gap configuration. Check valve ensures no flow back contamination to RO filter system & tank in the event the waste line plumbing clogs.

This one way valve has saved my sanity. I have a demand pump under my sink to increase the pressure from my RO to my fridge. Every 5-10 minutes it turns on for 1 second. This has become like nails on a chalkboard to me. I knew somehow the line pressure was dropping and that caused the pump to fire off. I could never find a leak so my only thought was pressure back flowing through the pump. I added this one way valve in front of the pump and miraculously it stopped. My nightmares have stopped and I get a full nights sleep now...

Works like a champ and like it should! Stuck on my Culligan on draw system’s air Feed line Because old one was spewing water out and it wasn’t supposed to do that. So now it only sucks in air and doesn’t let water escape out with this new thingy. Thank you. And I will Update if problem arises.

These work great for my gravity fed hydroponics system. They're definitely on the more expensive side, but I haven't found any similar products in this size on any other websites for a better price.

Well made but cracking pressure was too high for a drain application.

I bought it to prevent my R.O. system from draining out when the valve is shut. This is the perfect solution. The out tube has quite low pressure and there is still enough to open this check valve and to immediately shut to gravity flow completely off when the intake valve is shut.

Just what we needed for our milk vending machine

I do love John Guest connectors, but this one's a duffer. I've had these stick, crack and leak gas or liquid. The blocking activation force is really quite high so any movement less than "forceful" in the wrong direction won't be stopped.