Why do these connectors always leak!?!

[MrForbes]

Originally Posted by FrankJ

No strain on the tubing ie too short.

this is a common problem, cutting the tubing too short so it has to bend too tightly, and is pulled sideways in the connector.

[cmrnpizzo14]

Don't forget 3 wraps or so of teflon tape on the fittings!

[Jared]

Getting leak free connections can be tricky, but it's possible. Make sure that you cut off the tubing perfectly square. If you've already used a piece of tube in a connector, cut an inch off so that you have a fresh piece to grip.

Also, remember to put on teflon tape. It's important to wrap tightly and in the same direction as the threads on the fitting so it doesn't come off as you tighten it. I've found that using dry tape on a dry fitting works better.

Try not to get the tape too close to the end of the fitting. Leave a thread or so at the end, so that your tape doesn't come loose in the fitting and clog up the tiny holes in your solenoid valve. It's a pain to take the valves apart.

[MrBasse]

Don't forget to seat the fitting by pulling on the hose after pushing it all the way in. That ensures the barbs grab on tightly and also forced the collet tighter into the tapered section of the fitting.

You really should not need Teflon tape for a pipe fitting unless you had already used the fittings in question. But it is easy insurance for a leak free and happy day.