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Thread: 3/4 supply.....1/2 section.....3/4 run....

  1. #16
    Plumber Cass's Avatar
    Join Date
    Nov 2005


    What size line is feeding the house now and what material is it? If you have a PRV I would increase the pressure as high as you can get it. With 3 heads running at the same time you will need as many # pressure as you can get and the small piece of copper may affect it.

    What size is your water heater. At 7.5 GPM your hot water won't last long...maybe 10 min. or less depending on time of year and the temp setting of the water heater.

  2. #17


    I have two fifties in series for my hot water.

    I think I will try to change this small section of pipe, just to be safe.

    I will try to get to the tee in the wall without disturbing the adjacent bath. I will heat up the existing tee and pull it off the 3/4 supply. I can then either try to solder another tee (not very likely, but I'll try), or I bought a shark-bite tee that may work, but it's kind of bulky and this is a really tight space.

    Any other options for a confined space?

  3. #18
    DIY Senior Member TedL's Avatar
    Join Date
    Sep 2006
    NY Capital District


    Step back and think if any "outside the box" approaches might work.

    Can you get to the fitting from above/below/outside, rather than through the bath?

    Could you fish a new pex or copper supply line up to the location?


  4. #19
    Homeowner geniescience's Avatar
    Join Date
    Nov 2005
    humid summers hot, humid winters cold

    Default outside the box thought

    i have used Pex-Al-Pex (very malleable, and keeps its shape) to run a new line through a tight space with no access. You can use this to make a new run back to the HW heater or close to it.

    Aqua (Kitec) Pex-Al-Pex pipe has a huge __HUGE!__ diameter, far greater than 3/4" pex and also greater than 3/4" copper. I could find its true dimensions somewhere on the company web site and post them here, if this needs to be known precisely.

    Since the pipe is a three-layer composite, with aluminum as the middle layer, it keeps its shape when you straighten it or bend it. This is a good feature when you need to send it through a tight space.

    Water flows quietly in 1.) a large I.D. pipe, that has 2.) smooth inside walls and 3.) gentle flowing curves. Since the pipe can be bent into curves, you don't have abrupt elbow changes of direction / plane.

    A brand new run back to your HW heater is also good for your shower since it supplies water on a dedicated circuit.

    p.s. if you remove the 1/2" or the Tee you are 99% committed. Hope this alternative gets to you before too late.
    Last edited by geniescience; 02-28-2007 at 07:11 AM.

  5. #20

    Default options for a confined space

    Consider bypassing the 1/2" bootleneck with a run a new pipe at 3/4" OR even 1" diameter (@ $3 a foot in Type L copper nowadays---PEX looks better and better). Pick the exit and reentry points into the existing line to be those easiest to work at. The water flow (7.5 GPM??) will favor the path presenting the lower total psi drop.

    Be safe,
    [In God we trust. All others, bring data ... ]

  6. #21

    Default " ... I really like those charts about the copper ..."

    A master plumber saying he's impressed---that makes my day.

    [In God we trust. All others, bring data ... ]

  7. #22


    If it's difficult or serious demolition to eliminate the 1/2" then as MPM suggested, plumb it the easy way... It will take 15 minutes longer to go back and replace the 1/2 with copper than if you did it in the original install... if it don't work like you want then stick the 12" piece of 3/4 in later.....

  8. #23

    Default Now it's 3/4 ALL THE WAY!

    I finally bit the bullet this weekend. I heated up the old tee and took it out, no problem. Somehow I was able to get enough indirect heat on the new copper fitting (from the extremely small access point I had to work with) to melt some solder (I made sure I used about 6" of solder just to be safe, since I couldn't see the joint and I could barely fit the solder back there).

    I did have to (blind) shoot the fire extinguisher a couple times into the wall cavity, though!

    Presure test worked, didn't burn down the house , and now since it's all 3/4" I don't have to worry about any restrictions (even if it's not a dramatic change, it always would have been in the back of my mind that it could be BETTER!)

    Thanks so much for all your suggestions!


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