How Do You Bleed An LST Radiator?

How Do You Bleed An LST Radiator?

Posted by Kelly on 05 December 2018 09:00:21 GMT

Bleeding an LST radiator is sometimes necessary if you’re finding that the heat output from them isn’t up to its usual standard.

Contour has been blogging about why you’ll sometimes need to bleed your LST radiators and the safest way of doing so.

Read on to find out more…

Signs Your LST Radiator Needs Bleeding

Bleeding a radiator is when you release the cold air trapped in the system that could be affecting the efficiency of your heating.

Signs that you should bleed an LST radiator:

  • The LST radiator is taking a long time to heat up
  • Cold spots on the top of the LST radiator
  • Condensation on the outside of the LST radiator
  • Higher heating bills as you crank up the temperature when the LST radiators aren’t performing as normal

LST radiators are built to be long-lasting and shouldn’t need bleeding on a regular basis.

You should check your radiators every few months but the average time between radiator bleeds should be around once every 12 to 18 months. Depending on the usage of the LST radiators, however, this can be longer.


How Do You Bleed An LST Radiator?

Always start by turning off the heating system and letting it go completely cold!

When you bleed LST radiators you will sometimes get fluid escaping and you don’t want to be scalded by boiling water as it comes out of the system.

Before starting, make sure you have a cloth with you; it’s important in case any water comes out.

Once the system is completely cool, use a radiator bleed key or a screwdriver to open the valve anti-clockwise. You should hear a hissing sound as the cold air leaves the LST radiator.

When the sound stops and water starts to appear, turn the key clockwise to close the valve and repeat the process on all of your LST radiators.

When you’re finished, check the boiler gage to make sure that the pressure is right. If it’s low, you’ll need to rebalance the system before turning the heating back on.

If the pressure is correct, you are free to turn the heating back as normal. You’ll find the system performs to it’s expected standard once again now that the LST radiators have all been bled.



LST radiators sometimes need bleeding to ensure that they are constantly performing to the highest standard. They should only need to be bled once every 12-18 months depending on how often you use them.

Warning signs that they need to be bled includes cold patches at the of the LST, a long warm-up time and higher heating bills as the system loses efficiency because of the air trapped inside them.

Always start by turning off the heating and letting the system cool down. You should also make sure that you’ve got a cloth with you in case of any water escapes while you are bleeding the LST radiators.

Would you like to find out more about how LST radiators can help you? Fill out the form below and a heating expert will be in touch!

Reference: Homebuilding & Renovating and Best Heating.


About Us

Contour produces a range of innovative, safe surface temperature systems for healthcare, education, mental health, commercial and secure sectors, working in close partnership and collaborating with architects, M&E engineers, NHS Trusts, local authorities, design consultants and contractors to deliver outstanding safe heating solutions.

Contour is the exclusive partner of BioCote® anti-microbial technology for LST and anti-ligature radiators.  BioCote® additives reduce bacteria by up to 99.9%. Contour combine an extensive range of colour-paints is  with BioCote® for a durable, high-quality finish.

Contour’s heating solutions offer secure, single-person quick access to radiator guard interiors for regular deep cleaning and maintenance.  Each year, Contour save the NHS millions of pounds in cleaning costs, therefore delivering cleaner, safer environments.  Contour is redefining the marketplace and therefore many regard us as a design and innovation leader within the industry.

Contour have a quality- first philosophy. Our customer-focused team possess a ‘can-do’ attitude, they take pride in developing solutions for your heating requirements.

Contact us at:

The Mansions, 43 Broadway Shifnal

Shropshire TF11 8BB United Kingdom

+44 1952 290 498

Twitter: @Contour_Heating

LinkedIn: Contour Heating Products Ltd


Topics: LST Radiator Guards, LST Radiators, news, Safety, Low Surface Temperature radiator guards, LST