Noisy Radiators

What causes a running water sound from the radiators?

Probably air in the radiators - vent them all. Instructions are in this site, but basically you need a key to open a small bleed screw somewhere near the top of the rads. Open the vent until you hear a hiss of air coming out. Leave it open until you get e squirt of water, then close it. You might want a small dish or bowl placed under the corner of the radiator to catch any water before it hits the floor.

If you have to do this frequently then there may be a problem with your heating system.

I always have cloth near key to soak up jet of water before I can close vent. If gas coming out can be lit and has a very pale blue flame you have corrosion of radiators. Ensure you have suitable inhibitor in system to prevent future corrosion.

Depending on the design of you heating system, venting a large amount of air from the rads may lower the system pressure. You may have to increase the pressure when you have finished. Look for a pressure gauge on the boiler. Allow the system to cool down completely, and take a note of the pressure gauge reading before you start venting any radiators. It should be between 1.0 and 1.5 bar. (14-22 PSI) Check it again when you have finished venting - if it has dropped significantly then you have a sealed system and will need to add water. Find a filling loop near the boiler, and with the system still cold, open the fill valve and add water to bring the pressure back up to where it was previously. If you have an open vented system, then the pressure will not have changed during the venting process, and here will be no filling loop near the boiler.