I have a constant problem with air locks in my central heating hot water system. The hot water does not heat up because of the air lock and I have to keep going into the loft to release the air from the highest point, sometimes every week. I assume this is because the hot water feed is about three feet above the top of the cylinder before it gets back down to the cylinder. I do not have the same problem with the rads and the pipes take the same route. Should I fit an air purger to the highest point of the feed for the hot water or do I need to do something more drastic.
You could fit an automatic air vent in place of the manual vent, but it shoudln't really be needed, and definately shouldn't need venting on a weekly basis.
From the boiler to the tank/cylinder the pipes should continually rise, there shouldn't be any fall or drop, if the pipes rise to the loft then drop to the tank/cylinder then thet's the problem. Get a plumber out to check and alter the pipework if necessary