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Thread: DIverter problems

  1. #1

    Default DIverter problems

    I'm installing a Kohler pressure balancing valve w/ diverter (K305 KS) and a fancy new Kohler shower tile (K8002) that installs flush with the ceiling. It's all hooked up with Aquapex, but during test with the diverter out (tub faucet mode) water continues to flow out the shower head slowly. Sometimes it takes a minute or so for it to start, but eventually it flows out the shower head at approximately 1/4 flow. We've tried replumbing with 3/4" PEX to the faucet and 1/2" to the showerhead to open the path to the tub faucet, and we've cleaned the diverter (twice, it's clean anyway) all to no avail. Any thoughts on this? With the diverter out it seems like all water should happily flow to the tub but it doesn't. I'm interested in getting a plumbing lesson now....
    Last edited by Terry; 09-15-2011 at 12:04 PM.

  2. #2
    Tradesman Plumber Kristi's Avatar
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    Aha! I had this issue this past spring, and with the wonderful advice of a certain pro on this forum, the problem was sorted out... check to see if the valve has been installed upside down.

  3. #3
    Plumber jimbo's Avatar
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    Upside down would certainly be a problem. I note on the installation instructions for the K305 it specifically mentions not to use plastic pipe between valve and spout. Must be hard copper or IPS; one elbow max. It says any deviation from these instructions may cause improper shower function such as you have.

  4. #4

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    You are correct that the instructions warn against using plastic and using more than one elbow, but they don't bother to explain why. Why would this be at the physics level? In this day and age, why would a manufacturer go with a design restricted in this way? In my particular application, getting around and through the framing doesn't lend itself to copper easily, but I'd be willing to run flexible copper if someone can explain the science involved.

    The button diverter is beneath the handle where it belongs. Is there anything I'm missing here?

  5. #5
    Plumber jimbo's Avatar
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    I do not know exactly how that valve is constructed internally; but the principle involved is this: you have house pressure coming into the valve. When the valve is opened and water flows, the pressure at that point drops and you do not have full house pressure in there. As water flows thru the tub spout, if that flow is restricted by too-small pipe, then the dynamic pressure within the valve can be high enough to force water up the pipe to the shower head. One might think the diverter valve itself would not allow a path for water flow, but that may not be true.


    This "phenomenom" is most evident in showers which use a plunger on the spout to divert. In these models, there definitely IS a path for water flow to the shower at all times, and only the pressure drop at the spout prevents it.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default shower

    Plastic pipe has a smaller hole in it. Because of the laws of mathematics, when a circle is reduced in size its area reduces at a greater rate than the diameter. In your case the PEX cannot flow as much water as the valve is delivering so the excess has to go up and out of the shower head. In this day and age, the rules of geometry are the same as when Euclid wrote about them.

  7. #7

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    I couldn't get a hold of Euclid so I called Bernoulli instead who said if he had any meat left on his fingers he'd run 3/4" PEX from the valve to the spout (open path) and 1/2" PEX to the showerhead (restricted path) to address the science involved here to which you allude but I'd already tried this....

    The water SHOULD go path-of-least-resistance to the spout only but, dam#@it, it climbs up and spills out the showerhead too.
    Last edited by Terry; 09-15-2011 at 12:05 PM.

  8. #8

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    Thanks to all who helped. All were essentially correct. The fix indeed was to run flexible copper (5/8 o.d. type L) from valve to spout with exactly one elbow (at the spout) To accomplish this I used 4 sections of copper (necessary due to the framing) all carefully lofted and joined with soldered couplings. Straight copper would have required 6 elbows! As all but the speediest of experts can appreciate, it took this weekend warrior a couple of hours, but now everything runs drip free.

    Makes one wonder why PEX is not made with identical I.D.s so this sort of thing isn't an issue, but I suspect that's a topic for a different forum.
    Last edited by Terry; 09-15-2011 at 12:02 PM.

  9. #9
    DIY Junior Member jodiegilbert's Avatar
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    Are there any suggestions for this same scenario only there is no access to the plumbing? The problem was not found until the wall was tiled on both sides. Would a pressure regulator help?

  10. #10
    Retired Defense Industry Engineer jadnashua's Avatar
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    I don't know of any bandaid that will resolve the problem without repiping at least the tub spout with full-port pipes/fittings.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  11. #11
    Moderator & Master Plumber hj's Avatar
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    Even repiping from the valve to the diverter with 3/4" PEX does not eliminate the problem, since the PEX connnector which is screwed into the valve ALSO has a smaller diameter. They CANNOT make PEX with the same i.d. as copper because the o.d. has to be the same, but the wall MUST be thicker, which automatically reduces the internal diameter of the tubing.
    Licensed residential and commercial plumber

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