Shower goes hot and cold: checking a thermostatic tap

Short answer: first clean the shower head and filters and see whether limescale is restricting the flow. If the temperature still swings after that, the thermostatic element itself may be stiff or worn. You do not replace or repair that element by feel; an installer comes for that.

👷 Calling in a professional is never unnecessary. Work on the tap itself, the cartridge and the water connections belongs to a certified installer, especially if the tap is built into the wall.

What should you look for?

• Flow: a scaled Luvio shower head or a dirty metal shower hose connection can change the spray and the feel of temperature. Descale loose parts away from the tap.
• Tap choice: a Zen thermostatic shower tap keeps the set temperature more stable than an ordinary mixer. Models such as the Zen thermostatic shower tap in chrome are exposed taps; built-in work always needs a professional.
• Renewing a loose set: a Aton shower set can fit if you replace the whole shower set and the connections stay the same.

What do you need?

• A Luvio hand shower if the old shower head is too scaled.
• A Fila descaling cleaner for descaling loose parts according to the directions.
• A water pump pliers set and a adjustable wrench with a cloth to protect chrome.
• An 12-litre bucket to soak parts and catch water.

Step-by-step plan

1. Test cold and hot separately: feel whether both supplies feel normal without opening the tap.
2. Unscrew the shower head and rinse filter and head clean. Refit everything hand-tight.
3. Check the hose for kinks and dirt at the connections.
4. If it still swings, stop. Have the thermostat assessed by an installer. Also read our blog about the rain shower.

Working safely

Wear work gloves with nitrile coating with descaler and safety goggles when undoing a head above you. Never work on a tap while the main stopcock cannot be closed and test calmly for leaks afterwards with a dry cloth. Hot water can surprise; warn housemates that you are working on the shower.

Why is the basin stable but the shower not?

That points to the shower tap, head or hose and not to the whole hot water supply. Still have an installer look if in doubt.

Can I replace the cartridge myself?

On some exposed taps it looks simple, but seals, size and type must match and the supply must be off. Leave it to an installer if you are not sure of the type.

Is the shower being renewed? Start with the layout in our blog on the bathroom configurator.

Read also: our blog on the thermostatic shower tap · our blog about the rain shower · our blog on the bathroom configurator

Where can you find everything for this job?

At Saniso, the online store for DIYers and professionals, you will find tools, materials and personal protective equipment for your job.

• Browse our construction tools and our workwear and safety.
• Create a customer account and order easily.
• Working on a bigger project or want to hand over the job? Request a project quote.
• Book a showroom visit, at least 24 hours in advance.
• Not sure which material suits your job? Get in touch with us.

In doubt about the approach? Feel free to call in a professional.

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