Cost to Fit a Thermostat to a Hot Water Cylinder in 2023 | Checkatrade
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Last updated on October 4th, 2022

Cost to fit a thermostat to your hot water cylinder

What is the cost of a professional fitting a thermostat to a hot water cylinder? We’ve covered the costs and answered FAQs right here.

A hot water cylinder’s job is to provide a ready hot water supply for showers, washing and other household chores. The cylinder contains a lot of pre-heated water, so it’s all set for when you want it.

Fitting a hot water cylinder may seem simple to an expert, but for a DIYer it can be a nightmare. If you’re comfortable with the plumbing skills required to swap your existing thermostat for a new one, then by all means have a go yourself.

If you think a bigger job might be needed – such as moving a hot water cylinder – it’s best to seek the help of a competent professional.

What is a thermostat?

A thermostat senses when the pilot light is lit, triggering the gas control valve to emit gas.

If this part stops working, it can’t detect the flame, so the control valve will fail to produce gas. This means you’ll no longer be able to relight the pilot – or even the burner. Once your thermostat breaks, replacing it’s the best option.

Thinking of doing this yourself? Before working on the thermostat, make sure you turn off your gas connection and leave the water to cool down.

How much does it cost to fit a thermostat to a hot water cylinder?

To ensure the job’s done properly, we recommend hiring a plumber. In which case, it’ll cost closer to £110 for installing a new thermostat to your hot water cylinder. The part itself can cost anything from £20 on top of the installation cost.

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How to fit a thermostat to a hot water cylinder

Here’s how to fit a hot water cylinder thermostat yourself in 15 steps:

  1. Switch off the power.
  2. Remove the screw on the heating element’s access cover.
  3. Pull off the cover.
  4. Fold the insulation back to expose the thermostat.
  5. Lift the tab on the top of the plastic shield and pull it off.
  6. Loosen the screws, securing the wires to the thermostat.
  7. Pull the wires out.
  8. To release the thermostat, pull the tabs outwards at the top of the thermostat bracket.
  9. Slide the thermostat up and remove it.
  10. Place the new thermostat in the bracket, ensuring it fits firmly behind the tabs against the tank.
  11. Reattach the wires to the new thermostat and tighten them firmly.
  12. Reinstall the plastic shield over the thermostat and heating element.
  13. Fold the insulation back in place.
  14. Reinstall the heating element cover and screw.
  15. Flip the house circuit breakers to the ‘on’ position.

how to fit a thermostat to a hot water cylinder

Hot water cylinder thermostats quotes

If you’re trying to find out how much it’ll cost to fit a hot water cylinder, you may need to contact a hot water engineer in your local area. We advise contacting at least three such tradespeople for price estimates so you can get the best rate.

If you aren’t sure where to start, you could use our ‘Request a quote’ tool to make life easier. Just enter the details of the job and post it. Then, you’ll be contacted by hot water engineers local to you with their quotes.


How do you change a thermostat on a hot water cylinder?

Fitting hot water cylinder thermostats is straightforward. You can do this by following the instructions mentioned above.

Where should a thermostat be placed on a hot water cylinder?

Typically, a thermostat is installed roughly one-third of the way up the hot water cylinder so it can measure the water temperature efficiently. If it drops under the desired temperature (normally 60-65°C), this triggers the boiler to come on.

To find out more about the types of boilers, what they are, and the types of heating controls available, take a look at our handy boiler advice guide – it’ll answer any of your boiler questions!

Does a hot water cylinder need a thermostat?

Yes, any hot water cylinder will need a thermostat because it helps keep your hot water at the appropriate temperature to avoid wasting energy keeping it warmer than needed.

how to fit hot water cylinder thermostat

How do I know if my cylinder thermostat is working?

Signs your hot water thermostat’s faulty include:

  • The cylinder or airing cupboard feel incredibly hot
  • Scorching water comes out of the hot water taps
  • Hot water comes out of the cold taps
  • You hear ‘bubbling’ or excessive noise coming from the hot water cylinder
  • You spot steam or moisture in the airing cupboard or roof space

You can test a thermostat’s working using a multimeter. A working thermostat should have a reading of zero or as near to zero as possible. So, if your thermostat doesn’t read anything at all, it means it’s broken and needs replacing.

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