Problems with leaks at push to connect fittings

We have a RO system that decided to quit working. All filters have been recently replaced. The pressure in the tank reads good. We replaced the membrane, since that has been a problem before. RO still not working, and we have leaks at the tee push to connect fittings. Replaced the fittings, and still have leaks. ?? My husband then tried to bypass the RO system and connect the cold water line to the fridge line directly......still leaks at the 2 ended (not a tee) push to connect fitting. Why are we getting these leaks? If we can't fix the RO system we're tossing it. But we are still getting leaks trying to connect the cold water plastic tubing to the fridge plastic tubing, at the newly purchased fitting. And yes, they are all the same size (3/8") Help!!

throw the push fittings out and buy

buy 3/8'' brass compression coupling and poly ferruls

I install a lot of reverse osmosis systems and always seem to find some factory fittings leaking. Maybe they are getting damaged in shipping or something

Compression fittings are much better than push fittings, but don't use them on the output of the RO systems, the RO water will leach minerals out of the brass.

We had a plumber out today. He clipped the lines....again, like we had. He replaced the push to connect fittings.....again, like we had. He used plumber's grease to connect the lines in the push to connect fittings. That's the only thing we had not done. And now it's not leaking anywhere.

It says right in the install manual to grease the rubbers. If you try and push the pipe in dry it will distort the rubber that makes the seal

But there ya go. Ya learned something out of it!