RO system plumbing - 1/4" OD PEX Connections

[Atomic1]

The inlet plumbing on my Culligan RO system plumbing is really giving me some headaches. At my tap from the main service, I have a reducer to a male thread for a 1/4"OD brass compression fitting. I had a 1/4" OD UT soft copper tube about 10' long, but the dang thing sprung a pinhole in 5 months (not kinked or pinched, the wall just failed). Think i'm going to switch out to a 1/4" OD PEX instead, but am having a heck of a time figuring out the proper way to make a compression fitting with this stuff. I know on the larger diameter pex, it's recommended you use an insert and a plastic ferrule, but not sure what the rules are on this small of a tube, can i use a regular brass ferrule compression fitting and be confident its not going to blow off in a few months? The 1/4" brass insert i have wont fit this sized pex.

Should I somehow try to source 1/4" OD type L soft copper tubing instead? I cant seem to find it anywhere.

 

[Reach4]

Should I somehow try to source 1/4" OD type L soft copper tubing instead?

You don't want to use copper for RO water. Use plastic.

 

[Sponsor]

 

[Atomic1]

For the inlet? there shouldn't be any RO water in the inlet. If there is, there should be concern about the copper throughout the rest of the house.

 

[Reach4]

For the inlet?

No. Copper should be good for the inlet. I don't know why it failed, and I understand a pinhole leak happened. That is troubling. Is that your own well, or city water?

I don't know that you will find PEX smaller than 3/8 nominal, but there is other plastic.

For the line to the RO tap or refrigerator, use plastic.

 

[Atomic1]

Well water. Unsoftened at about 11 grains. Inside of copper plumbing elsewhere in the house has looked good without any significant deposits. Pressure is around 40-50psi.

I have 1/4" OD PEX on my desk. My question pertains to making compression connections with it.

 

[Atomic1]

Maybe I'll be more specific. When utilizing a brass compression fitting with 1/4" OD PEX (also known as 1/8" pex), do you need to use the plastic delrin ferrule and a stiffener? I can find plastic ferrules, but I dont think they make stiffeners for this small of an ID.