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pex size

Eric_51 Member Posts: 30
to best match baseboard should i use 1" or 3/4 "

the pex is smaller and then you put the fitting in and make it smaller yet. i wondered if this had a measurable effect on the flow.


  • Rich_49
    Rich_49 Member Posts: 2,710

    piping arrangement will you use ?  Parallel , series loop ?
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Ironman
    Ironman Member Posts: 7,114
    edited February 2014

    Pex has almost the same flow rate as copper. The barbed fitting can be restrictive and should be used very sparingly. The ideal thing would be to run the pex all the way back to the manifold with no fittings, but that's not always possible.

    Two things, one essential:

    First, you MUST use oxygen barrier pex, not plumbing pex.

    Second, type A pex is "memory" pex which means it will return to its original size after expansion. Several manufacturers offer expansion fittings which do not reduce the I.D. of the pex. The Uponor ad to the right pictures one brand. It does require a special tool, but it's a much better method than barbs with crimp rings.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    Don't forget….

    PEX has a high coefficient of expansion that MUST be taken into consideration, otherwise expect a lot of ticking and clicking as the tube expands.and contracts.

    It CAN be accommodated but requires fore thought to avoid issues.

    Think like PEX… Locks, glides, slides and free play.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Ironman
    Ironman Member Posts: 7,114
    Another Option...

    Pex-al-pex is a composite of pex and aluminum but acts very similar to soft copper including its co-efficient of expansion. In simple terms, it won't act like a piece of spaghetti when heated the way that regular pex does and is usually a little less expensive than type A pex with an O2 barrier.

    I have installed countless miles of it and it's usually my first choice for what you're describing.

    It's also listed as pert-al-pert. "Pert" means poly ethylene raised temperature.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Eric_51
    Eric_51 Member Posts: 30

    How do you make provisions? would you hold tight in the middle and let expand out. I want it to look nice in the crawl space.

    My longest loop will have 10 fittings including the ends, will the drop be to much, should i use 1" to make up for it.

    not getting into all the mumbo jumbo about extrusion process, other than flexibility whats the diff in a or b, and does it effect using it for copper fin tube?

    The pex al pex is good, but i have ring clamp tool and cant justify the other for 30 connections
  • SWEI
    SWEI Member Posts: 7,356
    Looking nice for PEX

    requires a LOT of hangers, and even then it will droop when the fluid temp rises.  A couple years back, we started using steel wall track to support insulated PEX, and have refined it to the point where we are quite comfortable with the results.  2-1/2" track is a perfect fit for a single run of insulated 1/2" or 3/4" pipe.  Two 2-1/2" tracks can be supported with a single 3/8" rod, where wider track requires either two rods or drilling of the track.  4" of strut will support a single run, 6" will support a double.  Once the strut is installed and the hardware is tight, simply lay the track on top and screw it in with #6 or #8 x 1/2" self-drilling lath screws.  The photos below have 10" of strut, which will actually support two 4" tracks (for larger pipes or more runs of 1/2".)  Zip ties hold the insulated pipe in the track.
  • bob eck
    bob eck Member Posts: 930
    Pex tubing for baseboard job

    Take a look at using Viega fostapex tubing. It is a full diameter Pex tubing with aluminum for the oxygen barrier. This tubing will not grow in length and it will not droop when running 180deg hot water through it. Great tubing comes in 20' lengths or 150' rolls.
  • Ironman
    Ironman Member Posts: 7,114
    Pex A or B

    Pex A is the highest quality and has a life expectancy of 200+ years. Pex B is inferior, has a 25 year life expectancy and is almost surely made in China. Pex B cannot use expansion fittings. I would not consider using it.

    Pex requires support at 32 inch intervals minimum and will expand in any direction it can.

    Let me put it in perspective:

    A 3/4 inch x100 ft length of pex will grow in length about 12 inches when it's temperature is raised 100*. That's about the normal amount of temp rise between on and off cycles with BB heating. Think about it: your pipe will be growing and shrinking one foot in length between each boiler cycle.

    Now look a 3/4" length of 100' copper. Under the same conditions, its expansion will be about an inch. And it will still retain its lateral stability.

    Pex-al-pex has almost the identical characteristics as copper and it also retains its lateral stability.

    Now before you write off using it, please listen to the advice of a pro who has run miles and miles of it as well as pex and copper. You can buy compression fittings for it and all they need are two adjustable wrenches. You don't have to use press fittings.

    Secondly, when you bend it, it stays put, just like soft copper. You can even use a tubing bender to make perfect bends, but it's not required. That ought to lower your fitting count also.

    Third, it has a larger internal diameter than pex and carries about 30% more than pex in 3/4 and 1" sizes.

    Fourth, it only requires support at 8' intervals.

    Without knowing how much radiation you're connecting to any loop it's not possible to know what size pipe should be feeding it. But, 3/4" copper or pex-al-pex will carry up to 4 gpm which translates to 40k btu's in a standard BB system. That translates to 80' of BB at 170* average water temp. I doubt that your loop will have anywhere near that much and if it does, the loop should be split.

    You ask for a pro's advice and more than one has pointed you to pex-al-pex. FostaPex is a brand of it.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    edited February 2014
    Making provisions for expansion

    On a long horizontal run, I will place a 360 degree loop in the center of the run. I will then "lock" the tubing down on the ends, using whatever method serves your application best, will remain robust through its life, and can handle the rigors of torque.

    I use glides at every framing member penetration (mickey mouse ears with only one screw applied) so that the EVOH barrier doesn't squeak, click or tick when it comes into contact with the framing members.

    On relatively short runs, you may be able to lock one end down, and allow the free play to push against a long leg of copper where the riser goes up to the BBR.

    The alternative to the 360 degree loop is do the conventional U tube expansion joint, but that chews up 4 elbows, with an equivalent length of 4 foot per elbow would = 16 foot of pipe, PLUS the actual pipe legs of the U. The 360 degree loop is = 2 X pi X radius, and in a 16 " joist bay, it will be a lot less footage than the U tube (2 X pi X 7" radius = 44", or 3.6 linear feet) representing a significant decrease of pipe equivalent length .

    Place a sheet of polyethylene plastic between the touching portions of the circle to avoid it clicking and ticking upon itself if you can't get a difference in elevation going into and out of the loop to keep it from coming into contact with itself.

    Now you probably know a lot more about plastic pipe and expansion joints than you wanted to, but done right, it saves time, and money and works silently. Done wrong, you will hear your heating system every time it turns on, and that is not part of my definition of "comfort".

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Eric_51
    Eric_51 Member Posts: 30
    pex al

    did some looking and found the fittings to use the pex al that didn't involve first born.

    the fittings have o rings do i worry about them going bad? the best warranty on comp fittings is 3 years, I'm assuming it has to do with the brass from corrosion

    Will i have to do anything special were the pex al goes through the floor or just treat it like copper. and what about hanging it some as pex .