Thermostatic shower system 1/2" enough or need 3/4"??

Discussion in 'Shower & bathtub Forum & Blog' started by mcu, Nov 17, 2011.

  1. mcu

    mcu New Member

    Messages:
    39
    Location:
    Montreal
    Hi,

    We are doing a remodel and will be installing a shower system with four body jets, a rainfall showerhead and a handheld shower wand. I have three options, and have been debating which to pick. Obviously the third is the best but also much more$$. So here goes

    1st option is 1/2" main thermostatic valve with 1/2" stop valves for the jets, shower head and wand.
    2nd option is 3/4" main thermostatic valve with 1/2" stop valves for the jets, showerhead and wand.
    3rd option is 3/4" all around.

    The company that makes the 1st option claims they 1/2" valve is better than most 3/4" valves made by the competitor but is that really true? Do I really need 3/4" or is 1/2" enough to run the jets and the head at same time?
  2. Terry

    Terry Administrator Staff Member

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    What products are you thinking of using?
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Location:
    New England
    In pipe, with no restrictions, going from 1/2" ID to 3/4" ID more than doubles the volume you can flow. The internal design of a valve can make a difference, but even open pipe with 1/2" you'd be hard pressed to get 7-8 gpm output using mixed hot/cold (and less with all one side).

    So, depending on the total volume of water you'd be using at one time, that would suggest the proper supply. Generically, it doesn't matter which type of valve, mixer, thermostatic, etc. it is, generally, you'll get more flow with less of a pressure drop with a larger valve AND supply lines. Those larger supply lines need to go all the way back to the supply. the other big consideration is the size of your water heater...it needs to be significant if you want anything other than a short shower.
  4. mcu

    mcu New Member

    Messages:
    39
    Location:
    Montreal
    two of them are local canadian companies (jalo and Royal) and the third is Aquabrass which is several hundred more.

    I have a 60G water heater
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
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    Location:
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    Look at the specs on the outlets you want to use at once. A body spray may use 1gpm, or more or less; so let's say 4gpm. A rain shower head is likely in the order of 2.5g. Now, if you want the handheld on at the same time, too, add another 2.5gpm, so you're up near 10gpm which a 1/2" valve will NOT support, at least in a manner you'd want. When the supply can't provide the full flow, the performance drops. Now, at 10gpm, your wimpy 60-gallon WH is likely to only last 5-minutes or so on full blast. Large showers require a large commitment to supplying that hot water. Only when you know the actual flow requirements can you decide what you need for controls.
  6. mcu

    mcu New Member

    Messages:
    39
    Location:
    Montreal
    so in other words i am better off getting a good 1/2" valve since it will let me enjoy a shower for at least 10-15 mins and living with not having so much pressure at the jets while the rainshower head is on. Now my other concern is i was planning on using pex with either sharkbite fittings or brass fittings (most likely the brass ones since less chance of failure in the future), but then i have read that the brass fitting makes it a 3/8" flow and many experience problems with water dripping from the shower head while brushing their teeth at the sink.
    Anyone experience this?
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,003
    Location:
    New England
    You've misunderstood. First off, with 1/2" pex and everything on, you'd likely only get a dribble out of everything. If you want good performance, do NOT use pex, or if you do, you need to use a much larger diameter since the ID is much less than that of copper. Keep in mind that in figuring the area of the opening, you have to square the radius...so a small change becomes a HUGE differece.

    If you don't want to be dissapointed, either give up on the lots of body sprays, or get both a bigger WH and plumb it with 3/4" stuff, and not in pex unless you say go to 1", which would be about the equivalent of 3/4" copper. And, if the supply from the WH is 1/2, you'll need to replumb it with at least 3/4" copper or 1" pex.

    1/2" pex is good for one showerhead, and you may notice degradation if you up that to two.

    The documentation will state the flow...and the minimum supply to make it work.
  8. mcu

    mcu New Member

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    Location:
    Montreal
    documentation states 2.5gpm at 80psi, but does not say with what parts running
  9. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
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    Location:
    North Vancouver, BC
    If you use Pex then for sure use either 3/4" or 1" pex as the supply lines.

    3/4" pex is about the same size as 1/2" copper

    1" Pex is about the same size as 3/4" copper

    We built a similar shower and sent the supply over in 1" pex and the branches out from the thermostatic valves in 3/4" pex.

    I would go with your third option and give yourself the luxury of having full pressure any where you want it. If you want less water just don't open up the valve that much.

    Enjoy your new Spa!

    JW
  10. hj

    hj Moderator & Master Plumber Staff Member

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    The limiting factor is the size of the ports IN THE VALVE itself. I usually use a 3/4" valves, (inteconnected with 3/4"), and with 1/2" feed and distribution lines
  11. mcu

    mcu New Member

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    39
    Location:
    Montreal
    JW, i noticed you are in canada also, what do you use for valves? you ever hear of Jalo?
    Hj, what about you?
  12. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
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    Location:
    North Vancouver, BC
    The shower we did similar to yours was done with DornBracht fixtures.

    I rarely have input on the plumbing package as most times this is chosen before we are called.

    JW
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
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    Location:
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    Any decent spec sheet will show the flow rate of the valve...until you know what your fixtures will demand, you can't determine if the valve in question will be able to supply what they need. Then, you also have to determine what your actual supply pressure is, as you very likely won't have 80psi (the max normally recommended by code). Four body sprays using 2.5gpm total probably aren't worth installing, but then, that's me. A typical single showerhead (in the USA) is limited to a max of 2.5gpm.

    A typical 1/2" valve may spec in the 6-7gpm, a 3/4" valve may spec 14-15gpm. There will be variations on that, and those figures are based on copper pipe of the same size feeding the valve. Your results may differ. But, if you try to draw more water than the supply can manage, performance drops off radically.
  14. mcu

    mcu New Member

    Messages:
    39
    Location:
    Montreal
    i got you and thanks for all the help so far. I have a technical question then...if i had 3/4" copper from the main going to one side of the house and on that line i had to cut a section off (let's say 20-30% of total length) to reroute and used 3/4" pex and then transforms to 3/4" copper again, am I really restricting flow rate? I know in ventillation when you downsize the size of the vent it creates a pressure and pushes stronger, then you open back up again, but this is plumbing and i don't know if the same applies
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,003
    Location:
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    Fluids are fluids, but the venturi effect only really applies in a fairly short section...keep things in copper or go with 1" pex. Soldering isn't really all that hard.
  16. hj

    hj Moderator & Master Plumber Staff Member

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    The name is Jado, not Jalo, but we seldom use them.
  17. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
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    Location:
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    valve

    If you intend to use PEX, then forget the previous statements. Then you DO need 3/4" just to have the same volume available that 1/2" copper would have given you.
  18. mcu

    mcu New Member

    Messages:
    39
    Location:
    Montreal
    no it's really Jalo and I will use copper
  19. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    4,141
    Location:
    North Vancouver, BC
    http://www.jalo.ca/AWSFILES/DOCS/1352/1/ENS-6000-00-XX.pdf

    IS this your stuff?

    Looks like you will need a couple of 1/2" MPT fittings and from there you pick. I would sent the valve all the water it can handle and from there the real piping begins.

    Are you going to balance all the spray heads?

    JW
  20. mcu

    mcu New Member

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    Location:
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