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Why Is My Tub's Temperature Control Stuck or Not Changing the Water Temperature?

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 the temperature control is stuck and will not turn, or the knob turns but the temperature does not change, the cause is almost always a thermostatic control valve cartridge fouled by calcium, iron or other particles in the water. A TCV that only gives cold water, only hot water, or stays stuck on lukewarm no matter where the handle sits is the same problem from a different angle. The first thing to check is your water: scale on other fixtures or well water means the cartridge and its intake screens have very likely clogged, and cleaning or replacing the cartridge restores normal mixing.

Likely Causes

  • Mineral scale or sediment on the cartridge and intake screens, which stops the valve from mixing. How the thermostatic control valve works shows what the cartridge does and which faucet sets include one.
  • A governor and limiter that went back on out of their original orientation after an earlier service, which can send hot water through with the handle in the cold position.
  • No inline filter or mesh on the supply lines, so hard water reaches the cartridge unprotected. See protecting the TCV in hard water.

What to Check, in Order

  1. Confirm your faucet set actually has a TCV. The dual-lever 5-piece fast-fill faucet is not thermostatic, so on that set a temperature problem is a supply or valve issue rather than a cartridge.
  2. Shut off both supply valves to the tub.
  3. Have a licensed and insured plumber remove the cartridge: loosen the allen bolt and lift off the handle, remove the cover plate, slide off the governor, remove the washers and escutcheon, unscrew the collar using only its flat wrench area, then unscrew the cartridge.
  4. Clean the intake screens and the bottom of the cartridge, including the check valve, with a soft brush and a lime scale remover such as CLR, or fit a new cartridge. The full walkthrough is in TCV cartridge cleaning and replacement.
  5. Lightly grease the gaskets with lithium grease, reassemble without over tightening, and test the full range of the handle with the water on.
  6. Fit an inline filter or mesh on the supply lines if there is not one already, and clean it on the same monthly rhythm as your vinegar flush.
TCV Valve Replacement
Chapters in this video
  1. 0:00 Remove Control Handle And Cover The technician removes the control handle and cover plate after shutting off the water supply.
  2. 0:16 Remove Escutcheon Plate And Collar The technician removes the washers, escutcheon plate, and then unscrews the metal collar.
  3. 0:33 Unscrew Cartridge And Clean Screens The technician unscrews the cartridge and cleans the intake screens and cartridge bottom.
  4. 0:56 Replace Cartridge And Reassemble The technician lubricates and replaces the cartridge, then reassembles the collar, escutcheon plate, and control handle.
  5. 1:30 Inspect Water Intake Screen The technician inspects and cleans the water intake screen and check valve for calcification and debris.

The video shows the disassembly above, the cleaning of the screens and check valve, and the reassembly with lightly greased gaskets and no over tightening. Watch: Ella's Bubbles: TCV Valve Replacement with chapters and a full transcript.

When to Open a Ticket

The TCV carries a 1 year limited warranty, and cartridge fouling from calcium, iron or contaminated water is not covered, so a photo of the removed cartridge and its screens is the fastest way for the team to tell you what you need. Include your serial number, a photo of the faucet set on the deck, and a note on whether an inline filter is fitted. Cartridges and complete valves come through your Ella dealer or the team at ellasbubbles.com/support or (800) 480-6850; the warranty exceptions guide explains what the 1 year term covers.

Common Questions

Why does hot water flow when the TCV is in the blue cold position?
If the valve was recently serviced, the governor and limiter under the handle have usually gone back on out of their original orientation, and the temperature adjustment steps in the cartridge guide reset the stop. If it has never been apart, a fouled cartridge that can no longer blend is the cause, and cleaning or replacing it resolves it.
Why will the handle not turn past a certain temperature?
By design the TCV locks at 100.4 degrees Fahrenheit and the button on the handle lets you raise the setting deliberately. A handle that will not move at all, or is stiff to turn, is a scaled cartridge, and a lubricant on the handle will not fix it.
Can I clean the TCV cartridge myself?
The removal and cleaning of the Thermostatic Control Valve (TCV) cartridge should only be performed by a licensed and insured contractor or plumber. The video titled "Ella's Bubbles: TCV Valve Replacement" shows the entire procedure, including removing the control handle and cover, unscrewing the collar, and cleaning the intake screens and cartridge bottom, so you know what to expect when your plumber performs the work. This ensures the cartridge is properly cleaned and reassembled without over-tightening, and that gaskets are lightly greased with lithium grease.
Is a stuck temperature control covered by the warranty?
The TCV has its own 1 year limited warranty, separate from the lifetime parts warranty on the tub, and it does not cover cartridge malfunction caused by calcium, iron or other particles in the water. An inline filter or mesh must be fitted and cleaned periodically to protect it.

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.

Related guides

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