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Pex fittings and flow

MikeGMikeG Member Posts: 138
Just for my own education what effect is there on flow in PEX tubing wigh some of the fitings in use?  I'm installing a small radiant ceiling using 1/2" PEX-AL.  The compression fittings have an internal opening of 5/16".  In this case there are only two fittings one on each end of about 150' of tubing.  Also I see on manifolds most of the compression fittings have smaller internal openings.  Is this restriction just more of a function of adding an equivelent length of tubing?  Obviously these systems work, I'm just trying to educate myself.  My background is more with open drainage systems, ditches, pipe flow and flood control pumping systems not closed systems.  We use some of the same factors but in a different way, length of pipe, roughness, slope, velocity,  and head pressure due to gravity.  Thanks  Mike


  • hot rodhot rod Member Posts: 7,014
    correct you are

    there will be a small pressure drop thru that fitting, but in your case not enough to cause a problem. The actual pressure drop depends on the flow rate. The more flow you try to move the more pressure drop.

    At Caleffi we engineered the pex and PAP fittings to reduce this pressure drop. There needs to be enough brass in the fitting to take the compression force, when you crank the fitting down, so it is a balance act.

    Tapered fitting, inside and out, with dual o-rings and a segmented olive (ferrule) all add up to an engineered fitting. Let me know if you want a sample.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • WeezboWeezbo Member Posts: 6,232
    that seems to be an excellent solution ,

    Are there any couplings/ transitions made for one inch ?


    Are they transitioned thru British thread or ?

    Thank you.

  • hot rodhot rod Member Posts: 7,014

    we are a brass company and we make thousands of unique fittings.

    As you know the rest of the world uses the International fitting size BSP, British Standard Pipe, and metric diameter tubes. In some cases they cross over, like 1/2 CTS (copper tube size) and 15MM will cross over.

    28MM may work on a 1" CTS which would be 1-1/8" OD.

    We also built some brass and composite fittings that fit the GEO PE tube dimension, maybe that is a CTS size? We have couplings and MIP adapters for 3/4, 1, and 1-1/4 PE tube.

    Let me know what ID tube you have, I'll bring up some samples :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • WeezboWeezbo Member Posts: 6,232
    edited December 2013
    Thats sounds like Hydronic Heaven . : )

    I wanted to do a complete header in white pex al pex ,stepping away from the black iron on a boiler years back , and this sounds like your Caleffi adventure is the Bomb . ! lol...

    I have since seen some Swiss condensing boilers that look like they were built with stealth technology from another planet that have caught my eye .. .

    their's seemed to be piped avec swoopies in stainless and some press couplings ..

    Thank You again, Hot Rod ...,

    sometimes, i feel like the Canadian Mounty Dudly Do right , far from the beaten path in some remote un named forest ...*~//: )

    We waited for the Lost Wilo transit cargo liner to circumnavigate the Earth a few times over the years prior to it landing with the delta P Circs .. i think Boris may be still at large ...

    You have so many new experiences, parts, pieces and information and with your ability to see a solution , wow what a deal !

    there did not materialize on my first reconn mission to town an immediate purchase of 4 28 mm X 1" adapter /transition coupling buh some how the folks here will make them out of thin air next time around , ....

    i am optimistic now. *~//: )
  • GordyGordy Member Posts: 7,106
    Engineered is right

    I saw the Venturi profile in the section drawing before I read it .....genius.
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