Tub/shower hot water won’t work

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New Member
Sep 14, 2016
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My house has two bathrooms - the master bath is the usual toilet, sink and shower (no tub). The main bathroom has a bathtub with shower. I’m the only occupant of the house. The main bathroom is used frequently (toilet and sink) but it has been over a year since the tub/shower has been used (the grandkids grew up and don’t visit as much). I have discovered that when I turn on the tub faucet the cold water works fine, but when I turn the knob to the hot water, the water decreases to a fast trickle and doesn’t get hot. Does anyone have an idea as to what could cause this? And what would need to be done to fix it? It worked fine before (when the tub and shower were used frequently).


Just call me Macgyver
Supporting Member
Sep 28, 2014
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right here right now, over there later on.
brand name of the offending shower valve?
I assume it is the scald guard

if delta

The 13 or 14 Series Faucets
  • 1. Look for the set screw opening along the side of the faucet handle. Use a hex key to rotate the screw counterclockwise until you can pull the ...
  • 2. Grasp the sleeve around the faucet cartridge and pull it off the faucet to expose the cartridge body.
  • 3. Pull the small plastic disk off the Delta faucet stem to expose the scald guard. Note the writing on the face of the scald guard indicating the ...
  • 4. Grab the scald guard with your fingers and pull it from the cartridge. Turning the guard counterclockwise increases the water temperature ...
  • 5 Insert the scald guard back into the cartridge. The notches on the scald guard must fit between the slots in the cartridge. Each slot represents a 4 to 16 degree difference in the water temperature, and the range of the slots is limited to restrict the placement of the scald guard. The design of the cartridge will not allow you to rotate the guard too far in either direction.

    Slide the plastic disk onto the faucet stem. Push the sleeve over the faucet cartridge. Replace the faucet handle and tighten the set screw.

    Adjusting the 17 Series Faucets
    Grab the temperature knob cover with both hands and pull it from the faucet handle to expose the temperature knob screw. The temperature knob sits on top of the faucet handle. Wiggle the temperature knob cover up and down as you pull it off the handle if it appears stuck.

    Remove the temperature knob screw to release the temperature knob from the faucet handle assembly. Remove the knob to expose the black plastic scald guard.

    Grab the scald guard with your fingertips and pull it from the handle assembly. Rotate the guard counterclockwise to increase the water temperature and counterclockwise to decrease it. Each notch on the guard represents a water temperature difference of 4 to 6 degrees.

    Insert the plastic guard back into the faucet handle assembly. Replace the temperature knob, knob screw and temperature knob cover. Only tighten the knob screw enough to keep the temperature knob from wobbling; overtightening can damage the knob and faucet.


Jeff Handy

Pro Handyman, NOT A Pro Plumber
Jul 5, 2019
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Chicago suburbs
Pressure balance is most likely culprit, agree with Rickyman.

The pressure balance unit limits sudden too hot or too cold water being released during use.

There are different kinds of technology inside them, but all of them can stick to all hot or all cold, I have usually found they stick to all cold.