Quick answer
Close the stopcocks, remove the handles and trim and pull out the cartridge. If it drips when shut off, replace the flow cartridge. If it will not regulate the temperature, clean the thermostatic cartridge and the inlet check valves with vinegar; if the spindle does not move freely, replace it. Always use the manufacturer's exact reference and calibrate to 38 °C.
What you need
- Phillips and flat screwdrivers
- Set of Allen keys
- Open-ended or box spanner to fit the cartridge (24-30 mm depending on the model)
- Long-nose pliers
- Kitchen or bath thermometer
- Cloth to block the plughole
- Torch
- Thermostatic cartridge with the same reference (Grohe, Hansgrohe, Roca) from Leroy Merlin or the official distributor
- Ceramic flow cartridge if it drips when shut off
- Set of O-rings and check valves
- Silicone grease for bathroom fittings
- White vinegar and an old toothbrush
- PTFE tape
Step by step
- 1
Identify the make and model
Look for the name moulded on the body, under the handle or on the front plate: Grohe Grohtherm, Hansgrohe Ecostat, Roca or Tres. The cartridge reference changes with the model and the year of manufacture. Photograph the mixer from the front and every part you remove.
- 2
Turn off the water and relieve the pressure
Close the hot and cold stopcocks for the shower, or the main stopcock for the property. Open the valve until the water stops running and cover the plughole with a cloth so no screws fall down it.
- 3
Remove the handles
There are two: one for flow and one for temperature. Prise out the centre cap with the tip of a small screwdriver and loosen the Allen or Phillips screw underneath. Pull the handle off without levering against the tile.
- 4
Take off the rosettes and trim
The rosettes usually unscrew by hand, or with a cloth for grip. If they are stuck with limescale, apply hot water and vinegar for ten minutes. Once they are off you will see the two cartridge threads.
- 5
Note the position of the temperature limiter
The 38 °C safety button is fitted over the thermostatic cartridge. Before you take it out, photograph the calibration mark: it will help you refit it in the same place.
- 6
Unscrew the cartridge
With the right size of spanner, turn anticlockwise. If it is seized by limescale, drip a little hot vinegar onto the thread and wait. Normally it gives with a quarter turn of resistance and then turns easily.
- 7
Clean the check valves
On the hot and cold inlets there are small valves that stop water passing from one side to the other. Pull them out with pliers, clean off the limescale with the brush and replace them if they do not seal. If they are dirty, the valve mixes badly even when the cartridge is fine.
- 8
Check the cartridge
Move the spindle by hand. If it is stiff, scaled up or the expansion wax no longer responds, replace it. If it is fine but the O-ring is hard, change only the seals. If it drips when shut off, the flow cartridge is the culprit, and that is replaced separately.
- 9
Refit and calibrate to 38 °C
Grease the seals with silicone, screw in the cartridge without forcing it and fit the limiter. Turn on the water and measure with the thermometer: with the handle at 38 °C the water should come out at 38 °C. If not, take the handle off again and reposition the limiter until it is calibrated.
- 10
Test with a full shower
Run the water for five minutes, shut it off and check that not a drop falls from the shower head or the base. Wipe a dry tissue around the rosettes to detect any damp.
Why a thermostatic shower valve drips or will not regulate the temperature
A thermostatic valve has more parts than a single-lever mixer. There is a flow cartridge (which opens and closes the water), a thermostatic cartridge (which blends hot and cold using a wax or bimetal element) and two check valves on the inlets. When one fails, the symptom is different, and it pays to learn to read it before you open anything.
On the Alicante and Valencia coast, limescale is problem number one. It builds up on the thermostatic element and the check valves, the valve responds late and the temperature swings up and down on its own. The second is wear on the O-rings, which shows from seven or eight years on.
| Symptom | Likely cause | What to do |
|---|---|---|
| Drips from the shower head after shutting off | Worn or scaled flow cartridge | Replace the flow cartridge |
| Drips from the base of the handle | Cartridge O-ring | Replace the O-rings |
| Will not reach 38 °C or runs cold | Dirty check valves or badly calibrated limiter | Clean and calibrate |
| Temperature swings up and down | Thermostatic cartridge full of limescale | Descale or replace the cartridge |
| Hot water comes out of the cold inlet | Check valve not closing | Replace the check valves |
| Handle stiff or will not turn | Limescale or dry seal | Descale and grease |
How to fix a dripping thermostatic shower valve, by leak point
If it drips from the shower head or the spout after you have shut it off, the problem is the flow cartridge. It is a ceramic cartridge like the one in a single-lever mixer, and we cover it in how to replace a tap cartridge. It costs €12-35 depending on the make.
If it drips from behind the handle or from the rosette, the leak is an O-ring, and it is fixed with a set of seals at €2-6 and silicone grease. If damp appears in the wall, next to the valve pipework, stop using the shower and turn off the water: it is no longer a cartridge matter.
If it will not regulate the temperature, first rule out the external cause: hot and cold water pressure need to be similar. We do not touch a boiler or a water heater with low pressure, but we can check that the thermostatic valve is not the culprit before you call the installer.
Common mistakes with a thermostatic shower valve
- Replacing the whole mixer for a €30 cartridge. A new branded thermostatic valve starts at €120 and the cartridge usually fixes 90% of cases.
- Buying a universal cartridge without checking the reference. Thermostatic cartridges are not interchangeable between makes, and sometimes not even between models.
- Using bleach or chemical drain cleaners on the rosettes. They damage the rubbers and stain the chrome. For limescale, use white vinegar or citric acid.
- Removing the temperature limiter without noting its position. If you fit it wrongly, the water can come out at 55 °C. Always measure with a thermometer.
- Not closing the stopcocks and trusting the valve to shut off. A thermostatic valve does not cut off the water at the inlets: the water is still under pressure when you take it apart.
- Forcing a stuck rosette. If you break the tile or the rosette, the repair costs far more. Use hot water and vinegar first.
When to call a plumber for the thermostatic valve
Replacing a cartridge is a handyman job with basic tools. It stops being one when you cannot find the reference, when the rosette is stuck to an expensive tile, when the valve is concealed and the inlets are damaged, or when you have already tried new cartridges and the temperature is still not stable.
At Manitas Costa fixing a dripping tap costs €40-70 labour and replacing the whole mixer is €45-80. You buy the cartridge, or we buy it and you see it on the invoice. We arrive in 20-45 minutes in Valencia, Alicante, Torrevieja and Benidorm, and in 30-60 in Dénia, Jávea, Calpe or Altea. Send us a photo of the handle by WhatsApp and we give you a fixed price.
All the details are in plumber in Valencia and Alicante and how much a plumber costs. For the general case of dripping taps: how to fix a dripping tap. If the thermostatic valve is no longer worth saving, see how to replace a shower tap. We do not work on boilers or water heaters: we refer them to a registered installer.
Limescale, salt air and safe temperature on the coast
With hard water, a thermostatic valve needs maintenance. Every six months, take off the rosettes, clean the limescale with white vinegar and check that the handles turn without effort. If you live in Torrevieja, Orihuela Costa or Elche, twice a year is sensible. A filter on the incoming water supply to the property also prolongs the life of the cartridge.
There is another safety point: the 38 °C stop protects children and older people. After any repair, check the temperature with a thermometer. And do not mix products: if you have cleaned limescale with vinegar, rinse well before applying anything containing chlorine. If you live in Benidorm or Valencia, we have a plumber in Benidorm and a plumber in Valencia for check-ups. For looking after the rest of the bathroom, see how to descale taps and how to clean a shower head.
Frequently asked questions
How much does it cost to fix a thermostatic valve that drips?
The flow cartridge costs €12-35 and the thermostatic one €40-90 depending on the make. With us, labour to fix a dripping tap is €40-70. If the whole mixer has to be replaced, labour is €45-80. Everything at a fixed price before we start, with an invoice including IVA (VAT).
How often does the thermostatic cartridge need replacing?
Between ten and fifteen years in soft water, and between five and eight in limescale areas such as Torrevieja, Alicante or Elche. You notice it when the temperature takes a while to settle, swings up and down or the handle gets stiff. Cleaning it with vinegar once or twice a year puts off the replacement.
Why does only cold or only hot water come out of the thermostatic valve?
The cartridge may be blocked by limescale, a check valve may not be closing, or one of the two inlets may be arriving with less pressure. First check that both stopcocks are fully open. If hot water appears at the cold inlet, the check valve is failing.
Can I use a cartridge from another make?
Almost never. Thermostatic valves from Grohe, Hansgrohe or Roca have different sizes and threads, and even vary within the same make from year to year. Find the reference on the mixer box or on the body, or send us a photo by WhatsApp and we will tell you which one to buy.
Can a thermostatic valve be fixed without breaking tiles?
Yes. The cartridge comes out from the front, by removing the handle and rosette, with no chiselling. The wall only has to be opened if the leak is in the concealed pipework. That is no longer handyman work: it goes to a renovation plumber, whom we can recommend.