Same 3 radiators need regular bleeding

[Crossfingers]

Hi

Can anyone shed some light on why the three same radiators need constant bleeding? There's about 13 radiators in my house and it's a close vented system. Two of the rads are upstairs and one is downstairs. It's a old house and the rads have also been there for a while, my guesses are either they're full of clogging black stuff or they need balancing.

Thanks

 

[John.g]

By close vented do you mean its a pressurized system with a E.vessel?. If so. and you are getting air ingress then the system pressure should slowly rise and return to original pressure after venting without any top up, if it requires top up after venting then likely hydrogen build up from corrosion or whatever.