Cylinder Servicing, Repairs & Installations


Thompson Services carries out repairs, servicing and installations of all types of cylinders. A general annual service could help keep on top of unexpected repair costs and water leaks.


If your cylinder has failed and requires replacement, contact us to schedule an appointment to carry out a free no obligation quotation to replace the cylinder.


Manufacturers of unvented water heaters recommend that you have your water heating serviced once a year, and many home insurance policies and building block management companies require this. Annual maintenance will help to keep the water heater safe and in line with the requirements of G3 building regulations relating to the hot water systems. Details of what is included in the annual service are shown below.


Other types of water heaters such as thermal store or combination water heaters are not required to have an annual service. For these water heaters, we offer a 'system health check', which enables us to investigate all aspects of the water heater and provide a report showing the condition of the water heater and enables you to keep on top of the maintenance.


If an unvented water heater has not had a regular annual service there is a possibility that the rubber seals in the safety valves will have hardened. If the seals have hardened, they will not sit back correctly in the valve and will pass water. In this instance water will be visable through the tun-dish in the discharge pipe and the valve in question will need to be replaced before damage is potentially caused. We will provide a quote for the additional work to supply and fit a replacement valve. A service for unvented water heaters includes testing safety valves, recharging pressure vessels, cleaning the pressure refuction valve, checking electrical connections and providing a service certificate.


Risks associated with unvented systems


Unvented water heaters are safe to use if installed and maintained correctly through an annual service. They incorporate three levels of safety. Thermostats that prevent the water being heated above 60-65 degrees, high level cut outs that operate when water reaches 80-85 degrees because the thermostat has failed and a temperature relief valve, which operates if both of the other safety features fail and the water reaches 90-95 degrees. In addition unvented water systems also incorporate a pressure relief valve which operates at 6-7 bar.


What's included within a cylinder service?



The following tasks will be completed with the annual cylinder service.


  • Expansion relief valve testing
  • Temperature and pressure relief valve testing
  • Storage tank draining as needed
  • Combination valve/pressure reduction valve stripping and line strainer cleaning
  • Pressure expansion vessel check (if so quipped)
  • Expansion vessel pressure top up
  • Leak check
  • Main and boost immersion heater and thermostat function testing
  • Main and boost immersion heater resistance check
  • Electrical ground check
  • Service record completion certificate


What is the cost of a cylinder service?


  • Cardiff based properties, Newport, Caerphilly, Barry, Penarth - £50.00 inc vat


Please note the price of the service excludes any materials, if faulty parts are found on the service, a quotation will be provided to replace as a seperate costings.



How to book a cylinder service?


To book a cylinder service, the easiest way is to email in with your name and address a member of staff will then be in touch to confirm a suitable day and time.



Office - 02922 218411

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Thompson Services Heating, Plumbing and Bathroom's 21 Miskin Street, Cathays, Cardiff, CF24 4AQ