Servicing and maintaining your cylinder

A guideline for regular service, maintenance and care of your Mixergy cylinder.

Mixergy Care Plan

The Mixergy Care Plan gives you hassle-free warranty cover. You don’t need to log an annual physical inspection of your cylinder with us for your warranty to remain valid. We use remote diagnostics to monitor your cylinder. To sign up, simply choose your care plan options in the Mixergy app.

If you're not on the Mixergy Care Plan, your G3-certified Installer must submit an annual inspection to us for your warranty to remain valid.

The following is a guideline for homeowners about the essential components of an annual service. Please note, only certified installers should undertake the following steps. 

For the installer

Performing visual checks 

  • Look for any obvious defects or damage in the cylinder shape, connections, pipework, Mixergy controller box, and any Mixergy additional components (for example, the PV Switch, Solar Diverter or Heat Pump Kit).
  • Check all of the wiring on the cylinder, including the Mixergy controller. Ensure any loosely hanging cables are tidied with suitable clips and not left hanging against anything warm or hot.

Safety valve operation

  • Manually operate the temperature/pressure relief valve for a few seconds.
  • Check that water is discharged and that it flows freely through the tundish and discharge pipework.
  • Check that the valve reseats correctly when released.
  • Repeat the above procedure for the expansion relief valve.

Expansion vessel charge pressure

  • Turn off the isolating valve before the Pressure Reducing Valve or the mains stop cock to the system.
  • Open the lowest hot tap in the system to relieve the system pressure.
  • Unscrew the black plastic cap on the expansion vessel to reveal the Schrader valve; with the aid of a pressure gauge, ensure the pressure reads 3.0 bar.
  • If there is insufficient pressure within the vessel, top up the vessel using an appropriate pump and recharge to 3.0 bar.


With the mains supply turned off and the lowest hot tap open:

  • Using a spanner, unscrew the pressure-reducing cartridge and remove the moulded housing. The strainer will be removed with the cartridge.
  • Wash any particulate matter from the strainer under clean running water.
  • Replace the strainer and screw the pressure-reducing valve cartridge into the moulded housing.
  • Close the hot tap, turn on isolating valve or main stop cock to the system. Check for leaks.

Descaling immersion heater (if necessary)

With the mains supply turned off and the lowest hot tap open:

  • Isolate the electrical supply and turn off the boiler or heat pump.
  • Attach a hosepipe to the drain cock having sufficient length to take water to a suitable discharge point below the level of the unit.
  • Open the cover(s) to the immersion heater housing(s) and disconnect the wiring from the immersion heater(s).
  • Unscrew the immersion heater and withdraw it from the cylinder.


Take care when lifting the immersion heater from the cylinder, and work within safe working practices.

  • Carefully remove any scale from the surface of the element(s).
  • Ensure sealing surfaces are clean and the gasket is undamaged; if in doubt, fit a new gasket.
  • Refit the immersion heater(s), ensuring not to trap the gasket.
  • Rewire, check, close, and secure immersion heater housing cover(s).


  • Check that all electrical and plumbing connections are secure. Close the drain cock.
  • With a hot tap open, turn on the cold water supply and allow the unit to refill.


DO NOT switch on the immersion heater, boiler or heat pump until the unit is full.

  • When water flows from the hot tap, allow it to flow for a short while to purge air and flush through any disturbed particles.
  • Close the hot tap and then open successive hot taps to purge any air.
  • When completely full and purged, check the system for leaks.
  • The heating source (immersion heater, boiler or heat pump) can then be switched on.
  • Check the outlet temperature at the outlet closest to the cylinder to determine whether the immersion thermostat is operating correctly.

For the homeowner

Regular inspection of your cylinder’s safety equipment is easy to do and is recommended by Mixergy to ensure the continued safe operation of the product.

The short guide below details three components that should be inspected.

Check the tundish

The tundish is a small plastic device attached to the cylinder's pipework. It acts as a break in the pipework that allows you to see the flow of water through the pipe.

Firstly, check that the tundish is completely dry and that no water is dripping through it. If this is not the case, please contact technical support for guidance.


Test the Temperature and Pressure (T&P) relief valve

The T&P relief valve is attached to the side of the cylinder near the top and has a visible red knob on the front.

Give the knob a turn to test the valve. This should cause water to flow through the tundish.


Check the Pressure Release Valve (PRV)

The PRV is a valve attached to the incoming pipework of the cylinder. It generally has a red, blue, or black knob similar to the T&P valve.

Give the knob on the pressure relief valve a turn to test the valve. This should cause water to flow through the tundish.

If no water flows when either of these valves is turned, or there is a blockage in the pipework causing the water to spill out of the tundish, please contact technical support immediately.


If you suspect there are any other issues with your cylinder (e.g., low water flow or low water temperature), please contact us, and we will be happy to help.

Service Record

  • Ensure that your installer completes the service records at the rear of the installation and service manual for your records.
  • Don't forget to arrange your next cylinder service at an annual interval.

Regular maintenance of our cylinders is highly recommended as this helps minimise any risk of future breakdowns or failures. It can also improve the performance and efficiency of the Mixergy cylinder, keeping it in peak condition.

If you have any questions or concerns, please contact our Technical Support team, providing as much information as possible. Our team will be able to help.