How tight for Poly tubing? - DIY Chatroom

KE2KB · 03-25-2009, 01:50 PM

Hi;
I am installing a water filter, and making connections using Polyethylene tubing (3/8") to standard brass compression Tee.

How tight should I make the nuts (all brass) on this tubing. I am using the brass ferrule that comes with the fitting.

While I don't want to over-tighten, I don't want it to leak or be pushed out by water pressure (approx 50psi).

When I first tightened the nut the tubing pulled right out. I tightened further, and could no longer pull the tubing out (with moderate force), but it would turn (snubly) in the fitting.
Should the tubing still be allowed to turn while seated in the fitting with the nut tightened?

Thanks for your help.

FW

Edit:
This post is now obsolete. I have completed the job. Admin: You may delete this is you wish.

Just Bill · 03-26-2009, 08:31 AM

Tighten until it no longer oozes water, plus 1/4 turn. But pretty hard to overtighten metal ferrules.

zosoplumber · 03-26-2009, 08:42 AM

correct me if Im wrong guys, but isn't the metal ferrul for use with copper 3/8 tubing and a plastic ferrule is for the poly line? the metal will actually cut through poly.

Bob Mariani · 03-26-2009, 08:50 AM

Quote:

Originally Posted by zosoplumber

correct me if Im wrong guys, but isn't the metal ferrul for use with copper 3/8 tubing and a plastic ferrule is for the poly line? the metal will actually cut through poly.

no you are correct. The poly ferrules are used with poly and the copper with copper.

KE2KB · 03-26-2009, 09:41 AM

I was able to make the connection with the brass ferrule. The poly is pretty tough. I can't imagine the ferrule cutting through it.
I used the brass insert that came with the fitting. It prevents the tubing from being crushed.

This was going into a brass Tee, and the ferrules were captive to the nuts, so I would have to purchase separate nuts and poly ferrules if I had your info before I completed the job.

Anyway, the connection is not leaking.

Thanks

FW