Connecting 3/8" PEX to a standard water shutoff

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by ddmoit, Nov 28, 2012.

  1. ddmoit

    ddmoit New Member

    Messages:
    52
    Location:
    SE Tennessee
    Hi folks. I just moved to Tennessee from Michigan. I'm installing an under sink water filter. It's a unit that uses 3/8" PEX on both ends. The connection piece that they gave me to connect to my cold supply is useless for my circumstance. What's the best way to connect PEX to a standard cold water shutoff valve without using special tools? Can I use an old fashioned nylon compression fitting like the ones commonly used for ice maker connections?

    Thanks for your attention.
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    yes........
  3. ddmoit

    ddmoit New Member

    Messages:
    52
    Location:
    SE Tennessee
    Do I sense an impending qualifying statement, or am I reading too much into the trailing periods?
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,480
    Location:
    Cave Creek, Arizona
    What is wrong with the connection they gave you? There is no such thing as a "standard cold water shutoff valve", because there are many types of cold water shut off valves.
  5. ddmoit

    ddmoit New Member

    Messages:
    52
    Location:
    SE Tennessee
    IMG_8123.JPG This is what was provided.

    IMG_8097.jpg This is what I have. It fit my new Delta faucet perfectly. I can add a splitter to the top of the shutoff valve to connect my faucet and the water filter.
  6. Terry

    Terry Administrator Staff Member

    Messages:
    14,889
    Location:
    Bothell, Washington
    The adapter looks to be 1/2" pipe threads x 3/8" OD.
    Your shutoff is 3/8" comp or also considered 3/8" OD
    You may want to pick up a double shutoff for the wall fitting
    or a 3/8 comp x 3/8 comp x 3/8 comp tee for the top of your current shutoff.

    [​IMG]
    Last edited: Nov 28, 2012
  7. ddmoit

    ddmoit New Member

    Messages:
    52
    Location:
    SE Tennessee
    The triple 3/8 tee is what I ended up doing. I'm just concerned about the PEX compression fitting holding. I used a nylon ring, properly installed. I suppose it's no worse than the line going to the new Delta faucet. A leak would be bad in a hurry though.

    IMG_8124.jpg
  8. Terry

    Terry Administrator Staff Member

    Messages:
    14,889
    Location:
    Bothell, Washington
    They make inside sleeves for the tubing too.
  9. ddmoit

    ddmoit New Member

    Messages:
    52
    Location:
    SE Tennessee
    Yeah, I actually have one. In all the excitement of putting it together, I failed to use it.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,888
    Location:
    New England
    The inside sleeve provides a hard, smooth, round surface to support and mold the pex so the compression fitting will hold and seal properly. It is included for a reason, you should use it! The connection will be much more robust.
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,480
    Location:
    Cave Creek, Arizona
    The connection Tee they gave you was to go between a "flexible hose" supply line and the 1/2" MIP threads on most conventional faucets. Delta, because of their DST versions no longer uses the MIP connection which is what caused your difficulty. The "Add-a-Tee" adapter you used is what I would have used also.

    [​IMG]
    Last edited by a moderator: Nov 28, 2012
  12. ddmoit

    ddmoit New Member

    Messages:
    52
    Location:
    SE Tennessee
    Thanks for all the input. Jim, I'll add the sleeve. I have a dishwasher to install in a few days, so I'll be under there again.
  13. 180pilot

    180pilot New Member

    Messages:
    2
    Location:
    Bakersfield, CA
    Delta supplys no insert for DST Pex faucet installation?

    Installed new Delta DST kitchen faucet, and because supply lines were so long, I cut off the manufactured ends and opted to use the nylon compression rings supplied with the kit to 3/8" angle stop valve No insert is provided. Instructions say to turn compression nut 2 full turns after hand tightning, that seemed way too tight at first try, but hot water side let go within 15 min. flooding kitchen. I then retightened to much tighter and then removed tubing to see that nylon compression ring was crimping tubing. And did a pull test. I installed ring in correct manner and deburred end after cutting with standard tubing cutter. It's holding now, but I can't find any recommendation to use an insert inside Pex tubing except on your site here?????? It seems standard practice with softer polybutylene?????? A call to Delta, just produced a woman trying to blame me for not cutting tubing correctly!! I'm an aviation mech. and have been making tubing connections for 40 yrs. Tubing was cut square and deburred. Connection makes me nervious, I always turn off my outside incoming water valve when I leave home, because all my plumbing is 20 yrs old....
    Last edited: Jan 15, 2013
  14. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    No "oh by the way" will follow! The forum requires minimum 10 characters in a reply,...hence the dots.
  15. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,480
    Location:
    Cave Creek, Arizona
    quote; No insert is provided. Instructions say to turn compression nut 2 full turns after hand tightning, that seemed way too tight at first try, but hot water side let go within 15 min. flooding kitchen

    You discovered the reason why I NEVER cut the manufacturer's supply lines. I just loop them to use the whole thing.
  16. 180pilot

    180pilot New Member

    Messages:
    2
    Location:
    Bakersfield, CA
    I believe the Pex being so stiff, and wanting to stay curled was putting so much side load on the compression nut, it just felt as if it was getting tight against the sealing ring. At second try, I held the tubing so it was straight into the valve with no side load while tightening nut. All is well so far no leaks. But I'll confirm there were no inserts in the parts kit, nor did the instructions show any for the optional shortening of the lines. 9 days and Delta support still has no answer to my question. If I had it to do again, the unsightly under sink clutter looping of the very long amount of tubing would still be a consideration for me. I would think Delta had done some research on the two different methods before offering the option. I went to local hardware with piece of cut off Pex and tried to force a brass insert into it, it could not be done with just my hand and arm pressure against a hard surface as with the soft poly tubing. Are there special diameters of insert for 3/8 Pex??? If so my hardware store did not know of them.
    Last edited: Jan 24, 2013
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