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Thread: Pex to Kohler 6 port Thermostatic Valve and general design q's

  1. #1

    Default Pex to Kohler 6 port Thermostatic Valve and general design q's

    Hi,

    This is my first time trying to install PEX. I am putting a Kohler DTV system in my master bath (pic attached). Master Bath is on my second floor. Master Bath will have the following fixtures:

    - 1 toilet
    - 3 sinks (one in toilet room, two in main area - all with 1/2 faucets)
    - 1 whirlpool (with 3/4" faucets)
    - 1 steam shower (with one 6-port Thermostatic valve 3/4" hot and cold supplies, and one 1/2" pres balancing valve for hand shower)

    If I plan on using a manifold system, what is my best option for setting up this bathroom - manifold in basement or on 2nd floor?

    Is it best to have a single manifold in the basement below the bathroom, then use individual runs for each fixture? If so, then what size Pex would I run for the Main supply to the manifold and then from the manifold to the different fixtures - I have a mix of 3/4" and 1/2" fixtures.

    What is the best way to supply the 6 port valve, it calls for a 3/4" supply. If I use a manifold in the basement, the manifolds look like they typically have a 3/4" supply line and 1/2" feeders. Would I use (2)two 1/2 feeders tied back into some type of reverse mini manifold to attach to the 6-Port Valve and the Whirlpool given they both have 3/4" fixtures?

    My concern is running 3/4" pex thru floors and around turns, 1/2 seems like it will be a lot easier to work with.

    I also have a desire to use a Hot water recirculator. I am considering just circulating it to the manifold, rather then the furthest fixture. Any suggestion on the type of circulator and best way to use it?
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    Thanks,

    Steve

  2. #2
    Master Plumber nhmaster's Avatar
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    The appendix of your code book will have the charts you need to appropriately size the water supply. 3/4 x 1/2 maniflods will not be enough.

  3. #3

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    Any chance you have a code book, I am not a plumber so am a bit short on the appendix you mention.
    Thanks,

    Steve

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    Master Plumber nhmaster's Avatar
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    I think you can get one at Amazon, just make sure you get the one that your state uses.

  5. #5

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    One point to note - my well supply comes into the house and is reduced to 3/4" right at my Well Tank. So that 3/4" line is feeding my Hot Water Heater and all my cold supplies.

    Not sure if using anything larger then 3/4" would provide any benefit?
    Thanks,

    Steve

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    Plumber Winslow's Avatar
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    exactly what are you putting in the shower fixture wise? What is the part number of the 6 port valve you are talking about? Judging by what little information you have provided I would say run 3/4" up under the tub deck. From there you can tee off and run 3/4 to the thermostatic valve (depending on how many fixtures you have running from it). Then put your manifold under the tub deck and branch to the other fixtures. Run your return line either from one of the shower valves or off the manifold.

  7. #7
    Illinois Licensed Plumber SewerRatz's Avatar
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    Here in Illinois the local libraries carry the state code and the local amendments, so it would not hurt to check there for a code book.

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    Plumber Winslow's Avatar
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    A code book will not help you in this situation. Even if you got one it is unlikely you will be able to understand the graphs. After educating yourself how to use them you will be greatly disappointed in the time and money you have wasted as it still won't provide the info you are looking for.

  9. #9
    Master Plumber nhmaster's Avatar
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    Quote Originally Posted by ijs12fly View Post
    One point to note - my well supply comes into the house and is reduced to 3/4" right at my Well Tank. So that 3/4" line is feeding my Hot Water Heater and all my cold supplies.

    Not sure if using anything larger then 3/4" would provide any benefit?
    now you are beginning to put the pieces of the puzzle together. You are right 3/4 probably won't be enough and the entire water main will have to be enlarged starting at the well tank.

  10. #10
    Moderator & Master Plumber hj's Avatar
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    To answer the last question first, you might as well just circulate to the mainfold. Circulating from the furthest fixture will just give "instant" hot water at that one fixture, all the rest will just be circulated to the manifold anyway. As far as pipe sizing, if you run 3/4" to the mainifolds, tee off for the larger valves ahead of the mainfolds. The manifold is merely a set of stacked tees, there is no rule that you HAVE to attach everything to it.

  11. #11

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    The Valve I have is the Kohler K-682 (six port thermostatic valve), this will feed 4 body sprays that cycle and never be used all at the same time (max of 3 at once), a shower head, and a rain head. The valve has two 3/4" inputs. These 6 fixtures are all rated at around 2.5 gpm at 80 psi, my system is more like 40-60 psi, so I figuer 1.6 gpm per fixture. Thats 10 gpm if all 6 are on. The spec for the valve says "for optimum performance 3/4" dedicated supply lines are recommended".

    So one main question I have is would it be alright to feed two 1/2 runs from a basement manifold and T back togheter and out to the 3/4" feeds for this valve (and also for the whirlpool)? Will two 1/2 pex runs equate to a 3/4" supply need? I know the area of two 1/2" runs is equal to about 90% of a single 3/4" run, but not sure how the inner diamater sizes actually measure up and compare to each other and vs copper.

    Does 1/2 pex flow more or less then 1/2 copper, and same question for 3/4"?
    Thanks,

    Steve

  12. #12
    Master Plumber nhmaster's Avatar
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    You are asking us all to do your homework for you. One more time. Without running the numbers for flow, pressure and distance we just can not give you a thumbs's up or down. What I can guarantee though is that if you do what you propose the valve will work, but not necessarily as well as you would like. Also, why spend all that money and time to install a valve and system that you can't get the optimal performance out of? Sorry to be so vague but you really need a better understanding of hydraulics.

  13. #13
    Plumber Winslow's Avatar
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    Quote Originally Posted by ijs12fly View Post
    The Valve I have is the Kohler K-682 (six port thermostatic valve), this will feed 4 body sprays that cycle and never be used all at the same time (max of 3 at once), a shower head, and a rain head. The valve has two 3/4" inputs. These 6 fixtures are all rated at around 2.5 gpm at 80 psi, my system is more like 40-60 psi, so I figuer 1.6 gpm per fixture. Thats 10 gpm if all 6 are on. The spec for the valve says "for optimum performance 3/4" dedicated supply lines are recommended".

    So one main question I have is would it be alright to feed two 1/2 runs from a basement manifold and T back togheter and out to the 3/4" feeds for this valve (and also for the whirlpool)? Will two 1/2 pex runs equate to a 3/4" supply need? I know the area of two 1/2" runs is equal to about 90% of a single 3/4" run, but not sure how the inner diamater sizes actually measure up and compare to each other and vs copper.

    Does 1/2 pex flow more or less then 1/2 copper, and same question for 3/4"?
    if you re asking for professional advice why do you insist on doing it in an unprofessional manner. run 3/4 inch lines to the valve. If you are incapable of doing it correctly then either hire someone to do it right or get a valve that only requires 1/2 inch. two 1/2 inch lines may mathmatically equal one 3/4 but with the additional friction loss through the 1/2 inch you will not see the same gpm.

  14. #14

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    Quote Originally Posted by nhmaster View Post
    Sorry to be so vague but you really need a better understanding of hydraulics.
    If I had a better understanding of hydraulics I probably wouldn't be asking for help on this DIY forum. In the 4 replies you have taken the time to construct not once have you provided me any "better understanding" of anything, so I am not sure what the purpose of your responses are. If you are trying to point out I am not a master plumber, I think I made that obvious with my first posting.

    For those that are trying to help - thanks in advance.

    A contractor I am working with had suggested to me he would use two runs of 1/2" to supply the 3/4" valve intakes. I am trying to determine if this is a bad idea.

    Winslow
    if you re asking for professional advice why do you insist on doing it in an unprofessional manner.
    I am not insisting on doing it one way or another, just trying to learn what I can / can't do.
    Thanks,

    Steve

  15. #15
    Plumber Winslow's Avatar
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    Quote Originally Posted by ijs12fly View Post
    If I had a better understanding of hydraulics I probably wouldn't be asking for help on this DIY forum. In the 4 replies you have taken the time to construct not once have you provided me any "better understanding" of anything, so I am not sure what the purpose of your responses are. If you are trying to point out I am not a master plumber, I think I made that obvious with my first posting.

    For those that are trying to help - thanks in advance.

    A contractor I am working with had suggested to me he would use two runs of 1/2" to supply the 3/4" valve intakes. I am trying to determine if this is a bad idea.

    Winslow I am not insisting on doing it one way or another, just trying to learn what I can / can't do.
    Your contractor is as clueless as you are. Just run 3/4 inch to the shower and tub valves. Put your manifold under the tub deck and run your return line from one of the branches of the manifold. decide where you want to put your confidence, in a cornercutting clueless contractor or people who do it for a living. Remember once you have finished and are happy with the pennies you have saved you have to live with the results when the fixture doesn't operate properly. But don't worry they will still look nice. And that contractor will abandon you like a rat on a sinking ship when the walls are all closed up and your fixtures don't operate satisfactory.

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