I found that the hot water in one of the showers was very restricted. It has an american standard valve which I opened up.

At the back of the valve, on the hot water side only, there was debris in the line. Removing it fixed the issue. Fast forward 3 or 4 months later, same problem, same debris.

A bathroom faucet in a different part of the house has a similar problem, likely the same issue.

Whiteish, and a bit crumbly. I tried dissolving it in CLR, and nothing happened.

debris found behind the shower valve, restricting water flow on the hot side

I suspect this may be coming from my tank style water heater. Any ideas what this is, and how to fix it more permanently?


  • 2
    What is your water source (city, well, other) and what kind of water treatment do you have? Commented Dec 20, 2023 at 19:33
  • 3
    how long did you leave it in CLR for before deciding it had no effect? This appears to be classical "hard water minerals coming out of solution in the water heater" debris. Solved with a water softener on the cold supply to the water heater, or other treatments such as TAC or polyphosphate.
    – Ecnerwal
    Commented Dec 20, 2023 at 19:37
  • Do you have galvanized steel supply pipes? Commented Dec 20, 2023 at 20:16
  • Water source is city water. No additional treatment. I had it in CLR for about a week. The house piping is copper, and the supply to the house is also copper. Water quality report for the source peelregion.ca/drinking-water/reports/2022/SP_final.pdf
    – kolcun
    Commented Dec 20, 2023 at 21:11
  • If anyone else wants to read it, you can skip to page 43 of the PDF for the hardness, etc. report. It says below 8 grains a gallon. Perhaps the water used to be harder (leaving debris in the heater) and is now softer. Alternately, perhaps it is picking up hardness in the pipes.
    – mdfst13
    Commented Dec 21, 2023 at 9:43

1 Answer 1


After some more research, it seems this type of debris is generally from one of two sources.

  1. mineral deposits
  2. plastic from the dip tube breaking down

In my case it's the dip tube. The material floats in water, and doesn't dissolve in either vinegar or CLR.

Source: https://www.reddit.com/r/Plumbing/comments/us0gzx/can_anyone_tell_me_why_this_keeps_building_up_and/

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