shower valves

cruiser56January 13, 2014

I have a spa 4 body sprays, handheld, rainhead shower and installed a Kohler K-2971 Pressure Balancing valve with a K-728 transfer valve. The tempeture fluctuates a lot. I also have a tankless water heater. I read that pressure balancing don't get along well with tankless heater. This happens even when using one showerhead. So I think I need a thermostatic valve. But before I invest another $500+ I was want to get some opinions.

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I have the hansgrohe thermostatic valve and I love it . No temperature change on me .

    Bookmark   January 14, 2014 at 12:51AM
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Lillo do you have a tankless water heater?

    Bookmark   January 14, 2014 at 7:38AM
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Sophie Wheeler

It's not the valve. It's the too much volume demands on the heater in conjunction with the valve. You are asking for too much flow from the heater, and it can barely provide what you are asking. That puts it too close to the safety presets for a pressure balancing valve. It wouldn't work with a thermostatic one either. You need to either split off he body jets and install another heater or eliminate them entirely.

    Bookmark   January 14, 2014 at 7:58AM
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It seems to fluctuate even with the rain head only. Our other bath has standard shower valve works fine.

    Bookmark   January 14, 2014 at 8:03AM
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Agree with hollysprings, the first thing I'd look at is the tankless unit.

Figure out the total GPM that you are demanding in the bathroom (and elsewhere in the house), and what your typical delta-T is in the winter months. The tankless needs to be sized for the most demanding application. The coldest weather/water and the highest demand flow.

Example, here are some generic specs on the first heater I found:

â 35ðF rise at 6.0 GPM
â 45ðF rise at 4.57 GPM
â 77ðF rise at 2.6 GPM

You can see temperature performance drops off as flow-through increases. Your rain head could simply be pushing the tankless beyond it's ability to heat water.

When some tankless units struggle to keep up with hot water output, they throttle down and restrict the outflow of hot water, this can lower the pressure in the hot water line.

That could affect a PB valve more than a TS valve based upon the pressure aspect alone. But depending on how much the heater is struggling to keep up, you might still get the same cold shower with a thermostatic.

So replacing the PB with a TS valve might help. Or it might make no difference at all.

Properly sizing your tankless to the demands of the house and your environment would give you the best chance of success.

Good luck!

    Bookmark   January 14, 2014 at 11:25AM
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I'm impressed.

    Bookmark   January 14, 2014 at 7:23PM
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