Water pressure to 2nd floor shower

davetzJuly 11, 2010

Hello plumbing experts! Here's a question about water pressure and heat:

We have several fixtures tapped into both hot and cold water lines PRIOR to the bathroom fixtures. The problem, specifically, is that if someone is showering and someone simultaneously uses the kitchen sink, ie to wash dishes with warm water, the shower user suffers a very cold shower--with poor water pressure.

Is there a way to reconfigure these pipes--specifically the kitchen sink and the bathroom fixtures line so that the shower pressure/hot water is not interrupted so much when someone uses the kitchen sink? I know how to do the work (the plumbing w/copper or pex), it's the planning I need help with! Please find a rough diagram of our setup below and let me know if you need more detail.


dave From Drop Box

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I don't see how reconfiguring the pipes will help you. You can help us understand the situation with a little more info. What is the flow rate of the shower with nothing else on? You can measure how long it takes to fill a pitcher/bucket of known volume. Might as well check the kitchen sink also. Do you happen to know the water pressure at you house?

What part of the country are you in?

    Bookmark   July 12, 2010 at 9:46AM
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I agree, the piping sizing looks fine. Also are you no a weel or city water (assuming city water). Do you have a single handle shower valve? Or two handle? More info needed.

Take Care,


    Bookmark   July 12, 2010 at 1:25PM
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Chris and Dan - Thanks!
Being away from home for a couple days, I can tell you what I know; i will determine the other answers when I return.

How do I determine water pressure to house? Can it be read off the meter?

-City Water
-St. Paul, MN
-Single Handle Mixing shower valve

Thanks again..will post other answers upon return

    Bookmark   July 12, 2010 at 6:59PM
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Water pressure gauge. Cheap. (5-20 bucks) Common. Screw on to any spigot and get instant read. Available at any hardware store. Every homeowner should have one. For problems like yours, it's always the first question that needs to be answered.

    Bookmark   July 12, 2010 at 7:46PM
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Ok, here's the rest of the info:
-Water pressure at hose bibb = 60 PSI
- Shower head = 1.2 GPM
- Tub spigot = 2.4 GPM
- Kitchen sink = 1.7 GPM

hope this helps

    Bookmark   July 14, 2010 at 9:56AM
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Well you have plenty of static pressure (no flow) there must be a restriction somewhere along the line. How old is the water heater? Have you opened the tank drain valve lately to check for buildup in the tank? Do you have a whole house water filter which may need changing? Are all valves fully open? Was the shower installed by a pro and/or are the supply lines to the valve 1/2" copper? After checking these things, you may have to clean or relace the shower head and take the shower valve apart and clean or replace cartridge.

Hope that helps,


    Bookmark   July 14, 2010 at 1:24PM
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Do the simple stuff first. Measure flow from shower head full-hot, then full cold. After that repeat but turn on another spigot while it's flowing. Does the slowing flow occur on both lines or only hot? Remove the shower head and measure the flow volume from the stub. 1.2gpm flow is pretty low for a shower head. Could be easy diagnosis. If you're only getting 1.2 from the stub, move upstream to the valve. There is an obstruction someplace....hopefully downstream from a re-pipe. In any event all of the above will only take a few minutes and you'll learn something from it.

Otherwise, agree with dan martyn.

    Bookmark   July 14, 2010 at 1:35PM
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Sorry so long in responding--I've been away from home.
dan martyn,
There's no whole house filter, the plumbing to the bathroom is copper, installed by professional plumber. I suspect of the things you mention, it seems the shower head or perhaps the shower valve are the most likely culprit. Would a low-flow/water miser shower head possibly cause better performance?

Asolo- I'll try what you mention, especially taking off the shower head and measuring the flow then--this seems it could lead to some conclusions.
Thanks for all the help!

    Bookmark   August 2, 2010 at 4:08PM
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Simple solution here.

Do you have a pressure balance valve on your shower?

If so it is faulty and needs to be repaired and or replaced.

If you do not have one, you need to install one.

    Bookmark   August 2, 2010 at 8:17PM
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Manhattan42--Not sure if there is a balancing valve. Can you elaborate?
Can I take apart the shower hot/cold mixing valve and determine if it's there? If not, is that where it would normally be added? Thanks,

    Bookmark   August 2, 2010 at 8:22PM
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The hot/cold mixing valve IS the pressure and temperature balancing valve.

If you have a single handled control, it is a temperature and pressure balancing control.

Then determine who the manufacturer is and look for repair information on the web.

It's that simple.

    Bookmark   August 3, 2010 at 6:48AM
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