Shower Valve Problems... Maybe???

edqxJanuary 13, 2011

Hi Everyone,

I have just done a lot of work trying to get a decent shower in 2nd floor bathroom. I have replaced 1/2" pipe to 1" pipe for hot and cold mains. The pressure switch is set at 45/65. Pressure tank is in the basement. The shower line is 3/4" up to the ceiling of the first floor. It switches to 1/2" to the shower. I have approximately 2.3 gpm with only cold water on. 1.7 gpm with warm water and .851 with hot water.

The sink which is right next to the shower is Hot 1.6 gpm and Cold 1.5 gpm.

All measurements are approximate. I used a gallon jug and stop watch....

Any idea what is wrong? Is it the shower valve?

Thank you for any suggestions.

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Double-check that the cut-off valves are fully open.

    Bookmark   January 13, 2011 at 3:56PM
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Is the shower valve thermostatic?

If so, try turning up the temp on the heater so the valve is mixing in more cold. Thermostatic valves do not work very well unless they are mixing enough cold water with the hot. If it takes 95% hot and 5% cold to achieve the desired temperature, the resulting flow rate is rather low. That has been my experience with Hansgrohe thermobalance valves

They don't have the same problem mixing in minimal hot with the cold, the flow rate is strong in that case.

    Bookmark   January 13, 2011 at 7:27PM
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Thank you for the replies. The cut off valves are fully open. Yes, I believe the valve is thermostatic. I think the hot water is set fairly high now, but I will double check. But why would turning up the water temp increase flow? I am sorry but I am confused how that would work.... But, I am willing to try it. Will try it tonight. Thanks.


    Bookmark   January 13, 2011 at 8:20PM
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I'll defer to those more experienced, but I would be inclined to remove the cartridge and inspect for debris. You might be able to blow some bits of crud out of the thing.

    Bookmark   January 13, 2011 at 10:15PM
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Since you recently did the plumbing, this is probably the problem:
The thermobalance cartrige has an inner screen that needs to be cleaned. It is not the same as removing the cartrige. You don't have to turn off the water supply. You don't have to remove the trim plate, just take the valve handle off. The brass body of the cartrige has hex-shaped places so it can be taken apart with 2 crescent wrenches. The male part has a screen around the base that gets clogged up with debris. More debris comes through the hot water pipes than the cold, so the low-flow issue manifests itself exactly as you describe.

I clean my valves a couple times per year. When you go to put it back together, don't tighten it too much. It is a precision-fitted union with rubber gaskets. Only snug-tighten with the crescent wrenches to avoid damaging the soft brass.

I have always had low flow issues with mine unless the hot water is sufficently hot that the valve mixes in some cold water too. Since you say the water is already plenty hot, this is not the issue.

    Bookmark   January 14, 2011 at 6:09PM
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Thank you. I will check this when I get home in a few days. Thanks again.

    Bookmark   January 17, 2011 at 11:44AM
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Thank you! I replaced the shower valve and cleaned out the rough valve area and presto great shower. Thanks again!

    Bookmark   January 24, 2011 at 12:44PM
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