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Thread: Low hot water pressure in bath tub

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    DIY Junior Member fairacres's Avatar
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    Default Low hot water pressure in bath tub

    My bath hot water goes through a diverter, as does my bath cold water. The hot water comes out with very little pressure, where as the cold water comes out strong so I can never get a hot enough shower. Both pipes to the diverter feed off the hot and cold water pipes that go to the sink, which has both very good hot and cold water pressure. Is there something wrong with the diverter? Do I need to replace it for some reason? The system and all the pipes were installed maybe fifteen years ago. Thank if anyone can advise.

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    Forum Admin, Expert Plumber Terry's Avatar
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    Is it a single handle tub faucet?
    And is so, which model?

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    Moderator & Master Plumber hj's Avatar
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    Default pressure

    One possibility is a stuck balancing spool, but if that is the case, we would have to know the make and model of the valve to tell you where it is and how to repair it.
    Licensed residential and commercial plumber

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    DIY Junior Member fairacres's Avatar
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    Default Kohler diverter

    Quote Originally Posted by Terry View Post
    Is it a single handle tub faucet?
    And is so, which model?
    The model number is too hard to read with artificial light, inside the closet wall. I'll try again in daylight. I know it's a Kohler, with a single handle control lever and the tub spout has a diverter to direct the water to the shower head but the hot water to the tub spout comes out in a small flow too, just like the shower head.
    Thanks!

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    Retired Defense Industry Engineer jadnashua's Avatar
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    How hot can you get the water? Is it really a function of you can't get it hot enough? Most valves have an internal adjustment to limit how hot the water can get for safety. You may need to adjust that. Now, how to do it is a valve specific thing - there is no generic procedure that works on all. What kind of pipe is feeding the valve? If it has any galvanized steel piping, the hot will often start to rust out before the cold. Galvanized was somewhat common, but shouldn't really be used on any supply lines. If you do have this, it may be just so full of rust on the inside, that the volume available is quite low.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member fairacres's Avatar
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    Default

    Quote Originally Posted by jadnashua View Post
    How hot can you get the water? Is it really a function of you can't get it hot enough? Most valves have an internal adjustment to limit how hot the water can get for safety. You may need to adjust that. Now, how to do it is a valve specific thing - there is no generic procedure that works on all. What kind of pipe is feeding the valve? If it has any galvanized steel piping, the hot will often start to rust out before the cold. Galvanized was somewhat common, but shouldn't really be used on any supply lines. If you do have this, it may be just so full of rust on the inside, that the volume available is quite low.
    The pipes are all copper and were new fifteen years ago.
    The hot water flow is very little, while the cold water flows normal.
    I bypassed the heat control to try to get hotter water but the minimal flow is not enough water to shower with.
    I can't read the part number of the valve behind the closet wall. I'll have to buy a dental mirror to see if I can reach around and read it that way.
    I didn't have this problem before.
    Thanks for any advice.

  7. #7
    Retired Defense Industry Engineer jadnashua's Avatar
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    At 15-years, I think it will have a pressure balance spool valve in it. This could be either a separate thing, or built-into the cartridge. This could be stuck. Sometimes a good rap with a soft blow hammer or mallet can free them up, sometime (if you're lucky) you can take it out and flush it, often, it must be replaced. This valve can get jammed to one end if you open the shower valve when both the hot and cold water supplies are not on.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member fairacres's Avatar
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    Default

    Quote Originally Posted by jadnashua View Post
    At 15-years, I think it will have a pressure balance spool valve in it. This could be either a separate thing, or built-into the cartridge. This could be stuck. Sometimes a good rap with a soft blow hammer or mallet can free them up, sometime (if you're lucky) you can take it out and flush it, often, it must be replaced. This valve can get jammed to one end if you open the shower valve when both the hot and cold water supplies are not on.
    Thanks. I was thinking of maybe taping it with a hammer to see it the spool was stuck. I'll try tomorrow and it that doesn't work replace the unit.

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    DIY Junior Member fairacres's Avatar
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    Default Found problem

    Quote Originally Posted by fairacres View Post
    Thanks. I was thinking of maybe taping it with a hammer to see it the spool was stuck. I'll try tomorrow and it that doesn't work replace the unit.
    I opened the unit and found pieces of copper metal inside it. One of two copper plates in the unit had disintegrated. I bought a replacement part from Home Depot and now I get both hot and cold water once more.

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