You had a mixer shower fitted a few years back.
Now the lower temperature control is leaking.
That drip usually means a worn seal inside the valve.
On many Arezzo thermostatic showers, the fix is the cartridge.
Quick Q&A
Q: Why does it leak from the temperature control?
A: The cartridge seals are worn, so water escapes around the spindle.
Before you start
- Turn off the water to the shower.
- Open the shower to relieve pressure.
- Plug the drain so small parts do not vanish.
- Take a photo before each step.
Where the cartridge usually hides
If you can remove the face plate and handles, you are close.
Most valves hold the cartridge with rings, a clip, or a retaining nut.
Look for these common hidden fasteners.
- A tiny grub screw under the handle.
- A small cap that pries off with a flat blade.
- A stop ring that lifts off after the handle comes off.
Steps to reach the thermostatic cartridge
-
- Mark the handle’s neutral position with a pen.
-
- Remove the temperature handle.
- Slide off any trim sleeve or cover ring.
- Remove the stop ring, lock ring, and washer in order.
-
- Pull the thermostatic cartridge straight out.
Some cartridges stick due to limescale.
Wiggle gently and pull straight.
A strap wrench can help without scratches.
Fix options
Option 1: Service the seals.
Inspect the O-rings for splits and flat spots.
Clean the valve bore with a soft cloth.
Use silicone faucet grease on the O-rings only.
Choose a grease rated for potable water parts.
Option 2: Replace the cartridge.
If the stem is pitted, replace the full cartridge.
Victorian Plumbing sells Arezzo thermostatic cartridges as spares.
Rebuild and set the temperature safely
Put the parts back in the reverse order.
Align any red marks and stop lugs as shown in the guide.
That alignment often targets a 38°C default setting.
Turn the water on and test for leaks.
Then check your max temperature and adjust if needed.
Helpful links
If you cannot isolate the water, stop here.
A plumber can swap the cartridge quickly and cleanly.
I’m Chris Mayer, writing for Plumbing 101.