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  1. #1
    Join Date
    Jan 2013
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    6

    Default Volume or Pressure?

    My main tub has really low flow. So low that the diverter hardly stays up and the water doesn't want to transfer to the shower head.

    I thought it was the valve so I replaced the main shower valve, spout, and shower head. It looks great but there is no difference.

    I called the city to check my pressure. According to the guy who came out, the pressure at the water tower (which I can see from my house) is 60psi. He measured 58 at my meter. He measured about 55 or 56 at the shower head. So it doesn't seem to be a pressure issue.

    The main line is a 1" copper pipe. This is reduced to a 3/4" for the middle part of the run, but all feeds off that 3/4" pipe are 1/2" lines. This is true for every faucet, appliance, the tub and shower in the master bath.

    What are we missing here? Do I need to replace all the 1/2" with 3/4"?

  2. #2
    Join Date
    May 2008
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    Default Re: Volume or Pressure?

    No, you don't need to replace all the 1/2" lines; that is a plenty big enough size. I would suspect another restriction in the line, such as a shutoff valve somewhere in the lines.

    No matter what the size of the pipe, you'll always get that same STATIC pressure reading if there is no water flowing anywhere in the house. A more meaningful test is to check the pressure at the showerhead while you run various faucets around the house (remove aerators first). That can help pinpoint the problem. For example, if the washing machine causes the pressure to drop but the kitchen faucet doesn't, that can indicate that both the shower and the washing machine are downstream of the blockage but the kitchen faucet is upstream.

    Do you have a pressure regulator? Sometimes those can cause this issue, but usually for the whole house.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  3. #3
    Join Date
    Feb 2010
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    1,227

    Default Re: Volume or Pressure?

    What type pipe do you have? If it's galvanized it may be time to replace it. Over time galvanized lines close done with build up inside the line.
    John

  4. #4
    Join Date
    Mar 2013
    Location
    WI
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    112

    Default Re: Volume or Pressure?

    Agree,they said the main line is copper,but are all the runs copper,or just the 1'"?

  5. #5
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    Jul 2010
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    SoCal
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    Default Re: Volume or Pressure?

    It's not very uncommon to see copper main line and galvanized wall pipes, especially in older homes.

    So what to do? you need access to the supply pipes to the tub - cut the drywall behind the tub. When you see what you have you can determine what to do next.

  6. #6
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    May 2008
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    Default Re: Volume or Pressure?

    With galvanized pipe, blockages are most common at fittings. This is because there is exposed, ungalvanized steel in the fitting's threads and the cut end of the pipe. This exposed steel will "grow" iron oxide (rust) deposits until the pipe literally closes off. Sometimes as a stopgap measure you can turn on the water and take a hammer and bang on the fittings and it will knock stuff loose, but that's only a temporary fix and doesn't address the real problem which is that galvanized steel pipes are not the best material for water supply.

    As for the ideal materials, either copper or PEX (cross-linked polyethylene). Certain water conditions are problematic with copper. I can't recommend CPVC because it gets brittle over time and can fail dramatically when frozen.
    Last edited by Fencepost; 10-24-2013 at 12:22 PM.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  7. #7
    Join Date
    Jan 2013
    Posts
    6

    Default Re: Volume or Pressure?

    All the pipes are copper. The city guy that came out came back because it was bugging him that he couldn't find the problem. He did a flow test by hooking up a hose at the meter and running it into the washing machine. He had about 25 GPM. also when he tested the pressure at the shower head with the actual head removed, he did run the water in the sink and the pressure hardly dropped at all.

    I'm going to test the flow rate at the tub spout today and see what that yields.

  8. #8
    Join Date
    Jan 2013
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    6

    Default Re: Volume or Pressure?

    So I ran water from the tub spout and got just under a gallon in 20 seconds. Doing the math it came out to 2.75 GPM. That seems pretty low yet I know some shower heads are set up for low flow to conserve water. Could my valve be set up that way? I'll see if I can find any info on the valve.

    Scott

  9. #9
    Join Date
    Jul 2010
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    SoCal
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    Default Re: Volume or Pressure?

    Your faucet falls in the average GPM rate, which is set by the manufacturers to stop reckless waste of precious water.

  10. #10
    Join Date
    Dec 2007
    Location
    Tennessee
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    1,791

    Default Re: Volume or Pressure?

    The problem is new water restriction regulations up against an old style diverter. From your description, you are using a tub spout with a pull up diverter built into the spout, those really needed a higher flow rate than current regulations recommend or allow. It does not appear that there is anything wrong with your plumbing pipes.

    New tub faucets have a restrictor in them. You have a 1/2" pipe coming into the faucet, but all that water has to go through a 1/4" or smaller hole to get to the spout or shower head. Bigger pipes are not going to help here.

    On the other side of the restriction, the pressure drops when water is flowing and that drop in pressure is too great to hold the diverter up. When you had the pressure tested, that was a static test. Pressure will build up in a static test to line pressure even if the restriction is only a pin hole, it just takes a little longer to build up.

    You did a flow test and it appears to meet current specs. To get a satisfactory spray at the shower head, the shower head has to flow less water than the faucet so that pressure is maintained.

    The next test would be a independent flow tests of the hot and cold water. They should flow about the same although the hot will probably be slightly lower than the cold. It is most likely going through more pipes to get to the water heater and back to the tub. The cold gets a more direct shot in most cases.

    My recommendation is to get either a three handle faucet, middle handle being the diverter or a single handle faucet that has a separate control for the diverter built in. While the faucet is off the pipes, check the adapter fitting that is soldered to the pipes for a big blob of solder blocking the pipe. That happened to me once, but it only affected the hot water, not the cold.

    Oh yeah, then you will probably want a new spout without the pull up diverter.

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