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Why Does Hard Water Keep Ruining My Temperature Valve?

Updated September 2026

▶Glossary5
  1. Likely Causes
  2. What to Check, in Order
  3. When to Open a Ticket
  4. Related Guides
  5. Common Questions

When hard water keeps destroying the temperature valve, the part that is actually suffering is the cartridge inside the Thermostatic Control Valve (TCV). Calcium, iron and fine particles in the supply settle on the cartridge and its intake screens, and the valve starts to stick or stops blending properly. The first thing to check is whether there is an inline filter or mesh on the water supply feeding the valve. The TCV must be protected by a filter or mesh that is cleaned periodically, and without one the same fouling will return no matter how many times the cartridge or knob is replaced. The protection details are in hard water TCV filter protection.

Likely Causes

  • No inline filter or mesh on the supply lines, so scale reaches the cartridge directly.
  • A filter that was fitted but has not been cleaned, so it has stopped doing its job.
  • Scale on the cartridge and intake screens that was never cleaned off, because only the handle or knob was replaced.
  • Very hard or iron rich water that needs the screens cleaned more often than usual.

What to Check, in Order

  1. Confirm a filter or mesh is installed on the supply to the valve. If there is none, have a licensed, insured plumber add one before anything else is replaced.
  2. If a filter is present, remove and clean it, then note how quickly it loads up again. That tells you how often it needs attention in your water.
  3. Have a licensed, insured plumber remove the cartridge and clean it and the intake screens with a soft brush and a lime scale remover such as CLR. The screen and the check valve at the bottom of the valve collect sediment and calcification and are easy to clean. The full procedure is in TCV cartridge cleaning and replacement.
  4. Lightly lubricate the gaskets with lithium grease, reassemble, and test the valve on both hot and cold settings.
  5. For the jet lines rather than the supply, run the monthly flush: mix 2 cups white vinegar with 2 cups water, fill to 1 inch above the highest jets, add the mixture, run the jets 10 minutes, then drain.

When to Open a Ticket

If the valve still sticks after the screens and cartridge are cleaned, or you would like to ask about Ella's cartridge cleaning service, contact your Ella dealer or the team at (800) 480-6850, or open a request at ellasbubbles.com/support. Include your model and serial number, a photo of the faucet set, and a note on whether a filter is fitted and how long ago the cartridge was last cleaned.

Common Questions

We replaced the temperature knob a year ago and it is sticking again, so what is going on?
The temperature knob is rarely the problem when your temperature valve is sticking; the cartridge inside the Thermostatic Control Valve (TCV) is what fouls with calcium, iron, and fine particles from hard water. These particles settle on the cartridge and its intake screens, causing the valve to stick or stop blending properly. To prevent this recurring issue, you need to clean the cartridge and screens, and protect the TCV with an inline filter or mesh that is cleaned regularly.
Is a fouled cartridge covered under warranty?
The TCV carries its own 1 year limited warranty, separate from the lifetime parts warranty, and cartridge sticking caused by calcium, iron or other particles in the water is not covered. See warranty exceptions for the TCV and faucets for the details.
How do I descale the piping in the tub?
The jet lines are cleaned with the monthly vinegar flush described above. The supply side is handled by the filter and by cleaning the cartridge screens; a licensed, insured plumber should do any work that involves removing the valve.
Is there a faucet set without the TCV?
Yes. The dual lever 5 piece fast fill faucet is non thermostatic, so a configuration without a TCV exists. Compare the options in fast fill faucets, 2 piece vs 5 piece and talk with your Ella dealer or the team about what fits your tub.
Can I clean the aerator and screens myself?
The intake screens clean easily with a soft brush and a lime scale remover once they are out. Removal and reassembly of the valve itself should be done by a licensed, insured plumber to keep the warranty in good standing.

About this guide. Answers in the Ella’s Bubbles Support Center are compiled from real conversations with tub owners, our technicians’ notes and the product documentation, then reviewed by our team. Tub models and options have evolved over the years, so a detail here may differ slightly from your exact tub. If something looks different on yours, send us your serial number and a specialist will confirm it for your model.

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