Kingston Plumbing

Preventing Radiator Issues

In this guide, you will learn how to prevent issues occurring with your radiators and central heating system. The basic tasks should be easy enough for any home owner to perform themselves. However, if you’re not confident in doing any of the tasks, you can contact us!

Adding inhibitor

Inhibitor prevents rust and sludge. What inhibitor does is prevents water from reacting with the metal of the radiator and components of the boiler, which creates rust, and in turn, creates sludge. You will find cold spots at the bottom of radiators, which could be sludge from rust.

Rust and sludge can block flow and return pipes (more common in micro-bore pipework) and can also find its way into the boiler and block the whole boiler.


To add inhibitor, follow these easy steps:

Open vented systems:
  1. If you have an open vented system (Identified by having a small header cistern in the attic), identify the correct cistern, as you will have 2 or more! You should be able to easily identify this as the smallest cistern, usually around 20 litres. The cold water cistern will be around 150 litres +
  2. Now you’ve correctly identified the feed and expansion cistern, you can simply pour the contents of the inhibitor into the tank.
Fully sealed systems (Combi boiler or Unvented Cylinder)

Tools you will need: Adjustable spanner, Channel lock grips, Small towel, Small jug (Or something to catch some water in),  Radiator bleed key.

  1. Find a radiator to pour the inhibitor into. This usually being a towel radiator in a bathroom or a small radiator.
  2. Turn the thermostatic radiator valve to fully OFF.
  3. Turn the lock shield valve to fully OFF (Turning clockwise), remembering how many turns it takes to fully close.
  4. Now using your radiator bleed key, open up the bleed valve located at the top of the radiator, and catch the water in your jug or small towel until the water stops.
  5. Now the pressure is removed from the radiator, keep the bleed valve open, this will help remove the water from the radiator.  Using your channel lock grips, hold the body of the radiator valve and use your adjustable spanner to open the nut on the radiator side of the valve, whilst the towel and small jug is underneath to catch the water. Remove around 1 or 2 litres of water from the radiator.
  6. Once enough water is removed, you can tighten up the nut on the radiator valve the same way you opened it.
  7. Now with the radiator valve water tight, remove the whole bleed valve from the radiator and pour the contents of the inhibitor into the radiator slowly.
  8. You can now reinstall the bleed valve, not forgetting to close the vent too!
  9. Open the lock shield valve the same amount of turns as when you turned it off in step 3.
  10. Re-pressurise the system to 1.5 bar and vent the radiator, the pressure will decrease as you vent the radiator, so keep re-pressurising the system until all air is removed from the radiator and the system pressure is between 1-1.5 bar.

Now when you turn on the heating, the inhibitor will evenly distribute around the whole system, radiators and into the boiler, protecting the system from corrosion, rust & sludge and decrease the likeliness of your boiler breaking down!


Magnetic In-Line Filter

Your central heating system should have an in-line magnetic filter installed on the return pipe, as close to the boiler as possible, when your boiler was installed, however, if not, you can install one yourself (if you’re confident enough) or contact us and we can help. An in-line magnetic filter will catch any rust and sludge that flows around the system, before it enters the boiler. If sludge enters the boiler, it can be very catastrophic for you and your boiler. If sludge enters the boiler, it can block and cost £100s!

Ensure you look after the filter! The filter should be cleaned at least once a year. To do that, it is very simple:

  1. Turn off both lever valves on the filter.
  2. Remove the pressure from the filter by using your bleed key and catch the water in a towel or jug.
  3. Using the provided filter spanner, open the filter to remove the magnet.
  4. With a towel or paper sheets, clean the filter; removing the sludge off the magnet and dispose of correctly (do NOT throw down the toilet or a sink/basin).
  5. Now the filter is clean, you can reinstate the magnet into the filter , ensuring the seal is 100% clean as this will help keep the filter water tight. Make sure you close the vent!
  6. Open the filter lever valves and ensure the system pressure is between 1-1.5 bar. If the pressure is low, top up the pressure using the filling loop by the boiler.

Thermostatic Radiator Valve

Thermostatic radiator valves control the temperature of the room, not the temperature of the water going into the radiator or the temperature output of the radiator. Many people will enter a room, feel that it’s cold, and turn the radiator valve to max! What this means is that the radiator will not turn off when it reaches a comfortable temperature, thus meaning you will be wasting energy and money! Each manufacturer have different values, but as a guide, the following should be followed when setting the thermostatic radiator valve to the temperature of the room:

1 – 10°C

2 – 15°C

3 – 20°C

4 – 25°C

5 / max – 30°C

The optimum temperature in a room should be between 18-22°C, thus meaning the best number to set the TRV to would be 3. Setting the TRV at 3 would mean the valve would automatically shut off when the room reaches a temperature of around 20°C. If there are rooms in your home that you don’t use much, turn them down to 1 or off, this will help save energy.


Radiator Not Getting Hot

During the summer your central heating generally isn’t used, this can make TRVs cease. If you’re finding that a radiator isn’t getting warm, but remember that it did work last time the heating was used. More often than not, you’ll find that the Thermostatic Radiator Valve pin will be stuck in the shut position.

  1. Using a pair of channel lock grips, remove the TRV head by turning the collar at the bottom on the head, anticlockwise.
  2. Locate the TRV pin in the middle of the valve, and try to push the pin down.
  3. If the pin does not move freely, use your channel lock grips to hold the pin, and push the pin down and up until it moves freely.
  4. Spray a bit of WD40 on the pin to prevent it from sticking in the future.
  5. Reinstall the TRV head and test the heating, checking that the radiator now gets warm.

Share with your friends

Related Articles

Kingston Plumbing

News, Information and More!

Our Customer service is our priority, this is why we have created a blog for our customers to find information on our services, or to fix your own plumbing problem

Our Favourites