Newbie question... how to measure flow rate of a shower?

Discussion in 'Shower & bathtub Forum & Blog' started by SliderJeff, Jul 25, 2009.

  1. SliderJeff

    SliderJeff DIY Member

    Messages:
    43
    Location:
    Houston TX
    Hey guys,

    Since I seem to be plaguing the forum with lots of questions tonight, it looks like I need to add a new one.

    How exactly would I go about measuring the flow rate of a give shower location in my home? Do I take off the shower head, get a graduated bucket and a stopwatch and time how long it takes to hit 1 gallon, or is there a better way to do it?

    I'm trying to pick a shower system or head and want to make sure I can accommodate it's needs when I pick it.

    Thanks,
    Jeff
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,798
    Location:
    New England
    If you remove the showerhead, you'll have unrestricted flow, and it would be similar to trying to fill the tub. The only way to measure the flow of a showerhead is with it attached. The manufacturers do that for you, and the info should be available as part of their specs. Federal regulations (in the USA) restrict a single showerhead to 2.5gpm maximum. Most use somewhat less. This is at some reference water pressure, and if your pressure differs, it will flow more or less. Many manufacturers use a restrictor (some can be easily removed) to limit the flow to meet the regulations of a showerhead.

    A typical valve can flow in the order of 6-8gpm if it is fed with 1/2" lines, and maybe as much as 13-15gpm if using 3/4" lines (the largest shower valve you'll find easily).
  3. SliderJeff

    SliderJeff DIY Member

    Messages:
    43
    Location:
    Houston TX
    Sorry, Jim... then I think I need to re-phrase my question. I'm not trying to measure the flow rate of the current head I have (I know it is less than stellar). What I'm trying to do is measure the water PRESSURE that I have in order to determine what head to buy. Some of the heads/systems I've seen listed seem to indicate that if you have less than stellar water pressure, you will have poor results if you buy a given head.

    If I'm looking at the Captains Quarters unit that Terry sells, I want to make sure that it's the current crappy Moen head that is causing my not-so-great showering experience and not the actual water pressure I get at this location in order to not be upset with a new head.

    Thanks for the help!

    Regs,
    Jeff
  4. SliderJeff

    SliderJeff DIY Member

    Messages:
    43
    Location:
    Houston TX
    Answering my own question after a little Googl-ing. :) Sorry for the trouble, guys. Hopefully this will answer someone else's question later:

    Go to a plumbing supply house and purchase a 100 PSI,( Pounds Per Square Inch) pressure gage. Now ask the salesman to add enough fittings on that gage to terminate in a 1/2" female IPS, (Iron Pipe Size)thread. You now have your pressure tester.

    To test your water system, remove the shower head from the bent chrome pipe coming out of the wall and screw on the gage. Turn on the hot and cold to the shower and read the pressure. The average house pressure should read between 40 and 50 PSI. A few pounds one way or the other is acceptable.

    Regards,
    Jeff
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,798
    Location:
    New England
    For about $10 you can buy a water pressure gauge. Pick one up at HD or Lowes, or a plumbing supply house. The easiest place to measure it is at a hose bib (the gauge will screw on like a hose). You can pick up adapters, and screw it onto the shower arm, but it should be within a couple of pounds as the hose bib. You could screw it onto the drain of the WH or a washing machine supply as well. Altitude changes will affect it slightly, but not all that much in a typical house.

    It you want to measure the velocity of the ouput of a showerhead...that's a totally different story....and a lot harder to measure.
  6. SliderJeff

    SliderJeff DIY Member

    Messages:
    43
    Location:
    Houston TX
    Thanks again, Jim!
  7. TedL

    TedL New Member

    Messages:
    604
    Location:
    NY Capital District
    Screwing it on a hose bibb (or laundry tray faucet, or clothes washer connection) will give you static pressure. If you have a relatively new, properly plumbed house, that may be all you need. If you have a house with 50 year old galvanized, it won't be.

    If you don't know plumbing age/type, you probably want to see what happens to the pressure as someone else draws 2-3 gpm of 98 degree mix from a faucet.
  8. SliderJeff

    SliderJeff DIY Member

    Messages:
    43
    Location:
    Houston TX
    Thanks, Ted. The house is only a little over 8 years old, so I'm thinking/hoping it should be of the fairly "modern day" style plumbing. I'll shoot over to Lowe's and/or Home Depot today and pick up the gauge and appropriate fittings to connect to the shower. Thanks!

    Regards,
    Jeff
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