Where does the air get into system

[Noisemaker]

Hi all

I am bleeding my three upstairs radiators every few days. I have no idea where the air is entering the system. Any input to help me deal with this problem will be appreciated.

Noisemaker

 

[wilhelm]

jeeezz noisemaker............ can you be a little more vague.

 

[namsag]

Are you bleeding with system turned off, as doing it with it on can pull air in.

 

[TexMex]

Could be that you have a build up of flatulent bacteria. As they fart, they produce gas bubbles. To check if this is the problem, next time you bleed the rads, catch the air that escapes in a pair of old underpants, and then attempt to ignite it with a lighter.

 

[Richardk]

It is could be gasses given off due to sludge in system,when heated produces gasses which require venting off. If the water that comes out when venting is black this is a sure sign and only real cure is a flush out with inhibitors added afterwards, or it could be your system not plumbed up correctly if it is a vented system and pump may be sucking in air through expansion pipe.

 

[ChrisR]

Air can also be sucked in through "micro leaks" on the ingoing side of the pump.
More boiler/system details please.