How Do I Clean or Replace the Thermostatic Faucet Cartridge?

Cleaning or replacing the cartridge in an Ella thermostatic faucet is a job for a local licensed plumber: shut off both supplies, remove the control handle, cover plate, escutcheon and collar, unscrew the cartridge, clean its intake screens and base of calcification, and reassemble without over torquing, or fit a new cartridge if cleaning does not restore mixing. Cleaning always comes first, because a fouled cartridge causes exactly the same symptoms as a failed one. Tub Fills Only Scalding or Only Cold and Will Not Mix to Warm covers the most common of those symptoms; this page is the procedure itself, plus how to decide between a cartridge and a whole valve and how to order either one.

When the Cartridge Is the Problem

The thermostatic control valve (TCV) is fed by a hot line and a cold line, and a single mixed line runs to the spout. The cartridge inside blends the two supplies to the temperature you set on the dial, and it is sensitive to calcium, iron and debris in the supply water. Once it is fouled, the reports look like this:

• Water that is either scalding or icy, with no handle position giving warm water.
• Water stuck very hot, or hot flowing with no cold coming through.
• Water measured at the spout with a bath thermometer that runs well above the dial setting, the case described in Why Is the Water in My Walk-In Tub Too Hot?.
• Hot and cold crossing inside the valve while the tub is off, so the rest of the home loses hot water until the tub's shutoffs are closed. Why Does the Mixing Valve Cross Hot and Cold When the Tub Is Off? shows how to confirm the tub is the source and rules out the hand shower check valve first.

Before anyone touches the cartridge, confirm from your order that your faucet package includes a TCV. Not every configuration has one. The dual-lever 5-piece fast-fill faucet, for example, is not thermostatic. Its hot and cold handles each have a small cartridge of their own that comes out from under the handle with an allen wrench and a socket wrench, and the 2-piece faucet has a similar handle cartridge with guide posts that must line up with the spout housing. Those are different parts and a different job from the thermostatic cartridge described here.

Step by Step: Cleaning the Thermostatic Cartridge

1. Shut off the hot and cold supplies to the tub at the shutoff valves behind the access panel.
2. Remove the control handle and the cover plate.
3. Remove the washers and the escutcheon plate, then unscrew the metal collar.
4. Unscrew the cartridge and lift it out.
5. Clean the intake screens and the bottom of the cartridge of calcification and debris.
6. Reinstall the cartridge, the collar, the escutcheon plate and the handle. Reassemble without over torquing.
7. Open both shutoffs fully and test the faucet through the full range of the temperature dial.

Ella has videos showing how to disassemble, clean and reinstall the cartridge, and the team can send the links for your faucet through ellasbubbles.com/support or (800) 480-6850. If the water still will not mix after cleaning, replace the cartridge with a new one. If the valve body itself has failed, replacing the whole TCV is the recommended repair.

The Cold-Inlet Check Valve Is a Separate Part

If the faucet delivers only hot water no matter where the dial sits, the cold line has pressure when disconnected at the valve, and the inlet screen is clean, the cartridge is probably not at fault. The one-way check valve at the cold-water inlet of the TCV housing can stick in the locked position or become blocked by sediment. To free it, shut off both supplies, disconnect the cold line from the valve, remove the spring and the screen from the cold inlet, rinse the screen and clear any obstruction, release the check valve so it moves freely, then reinstall the screen and spring, reconnect the cold line and test. Take a short video of the check valve and inlet before reassembly so the team can confirm the diagnosis if cold water still does not flow. The full procedure is in Cold Water Reaches the Tub but Will Not Come Out of the Faucet: Unlocking the TCV Check Valve.

Cartridge or Whole Valve, and How to Order

Which part you need depends on the generation of faucet on your tub. Take a clear photo of the valve body, the knob and the supply connections, note the serial number from the label behind the magnetic access panel next to the door, and send them through ellasbubbles.com/support or call (800) 480-6850. The team matches the part from the photo and confirms its current availability before anything is ordered.

• Older tubs used a thermostatic valve with half-inch inlets. That valve body has been discontinued, and in some cases the cartridge alone is the replacement for those units. A missing set screw can be matched at a hardware store.
• Current tubs use a three-quarter-inch thermostatic valve, and the team confirms whether the complete valve or the cartridge is the right part for yours.
• If a valve for an older faucet can no longer be matched, the thermostatic faucet can be replaced with an Ella fast-fill faucet, and the team will explain what that involves.

Replacement parts are ordered by phone with a shipping address, or through the parts order form, and tracking is sent when the part ships. Some Ella dealers can also help with thermostatic valves and service, so ask your dealer if you have one nearby. Replacing a Failed Thermostatic Control Valve: Cleaning First, Cartridge Versus Whole Valve, and How to Order has the ordering details.

Protecting the New Cartridge, and What the Warranty Covers

Fouling comes from the water supply, so fit an inline filter or mesh screen on the supply lines and clean it periodically. That protection is required for the TCV, and it is what keeps a freshly cleaned or new cartridge from clogging again. The TCV carries a 1-year limited warranty and is excluded from the lifetime parts warranty, and cartridge fouling caused by calcium, iron or contaminated water is not a covered defect. When a part is covered, Ella ships it under the warranty and a local licensed plumber does the labor. Ella does not send technicians. If cleaning the cartridge becomes a recurring chore in your area, tech support may suggest replacing the thermostatic faucet with the Ella 5-piece fast-fill faucet, which mixes with manual hot and cold handles and has no thermostatic cartridge to foul, though it does not hold a set temperature on its own.

Related Guides

• Faucet drips or the handle feels stiff: replacing your faucet cartridge step by step
• Replacing Your Walk-In Tub Faucet Set, Valves or Hand Mixer
• Leaking Diverter or Thermostatic Control Valve: Identifying Your Faucet and Ordering the Right Replacement

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