Balancing radiators without thermometers

After reading various DIY guides and articles on how to balance a radiator based heating system, I came across an interesting, but in-depth guide on how to do this without the cost of using thermometers, let alone hiring a plumber.  In my guide here, I aim to summarise the process, which is a little different to the original in-depth guide, but worked well for me despite me not being a plumber.

First of all, please only follow this guide at your own risk! While I haven’t had any issue so far with radiator valves, from my reading, adjusting the radiator valves may cause a leak, see this page (different website), which explains how to deal with a leaky valve.

Tools required:

  • Small adjustable spanner.
  • A Philips screwdriver may also be required.

Note: Each radiator generally has two valves, one with an on/off knob and the other used for balancing.  In this guide, I’ll call the one used for balancing the “Balancing valve”.

  1. Bleed all the radiators using a bleeder key to ensure no air is trapped in any radiators.
  2. Ensure all radiators are on and then switch on the heating system.
  3. If the circulation pump speed is set to ‘1’, change it to ‘2’.  This pump is usually located near the boiler.
  4. For a pressurised system, which is a heating system with an expansion vessel with a pressure gauge, ensure there is at least 1 bar (~14PSI) of pressure.  If not, open the value (usually a small knob) leading to it until the pressure reaches 1.5 bar (~21 PSI) and then close it again.
  5. When the radiators that get hottest warm up but not too hot to touch, feel the two pipes to verify the on/off knob is on the hotter pipe, as the hotter pipe is the one that feeds the radiator.  Take care, as the pipes can get hot enough to burn, especially if the system uses a powerful boiler.  Repeat this check with the rest of the radiators as they warm up.  Take note of any radiators that the hot water comes in on the end with the balancing valve.
  6. For each radiator, remove the cap at the end opposite to the on/off knob and carefully fully open up the valve, anti-clockwise like a tap.  Some caps require a Philips screwdriver to remove, while others simply pull off.
  7. Wait ~5 minutes to allow the radiators to warm up.
  8. If all the radiators are equally warm (very unlikely), then the heating system is now balanced and there is no need to continue further with this guide.
  9. On only the hottest radiators close the balancing valve to just over half-way open (~60%).  To do this, count how many full turns it takes to fully close it and then open it by just over half as many turns.  For example, if it takes 2.5 turns to go from open to closed, then close the valve and open it by 1.5 turns.
  10. Wait ~5 minutes to allow the adjustment to take effect.  If all the radiators now feel equally hot, skip step 11.
  11. On the hottest radiators, which include any additional radiators that became hot, close the balancing valve by half a turn and go back to step 10.  Note:  If this results in the valve fully closed, make a quarter turn instead.  For any radiators where the hot water is fed in on the balancing valve end, see if it’s possible to swap this cap with the cap on the other end.  If not, then don’t close the balancing valve by more than ~80% to avoid air bubbles coming in from being trapped, which can happen.
  12. When the heating system next turns on, allow 30 minutes to warm up and ensure all the radiators are roughly equally hot.  If any radiator fails to warm up or becomes lukewarm, open the balancing valve by a quarter turn.
  13. If the radiators still do not equally warm up, then it’s quite likely the circulation pump is failing, an isolation valve is not fully open or there is a sludge build-up in the system.

If this guide seems to go too quick or your need to read something in more detail, please see this in-depth guide which I based mine on.

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