Went to change a radiator for a friend yesterday, so turned the boiler off , isolated the cold feed to the tanks and commenced to drain down. While that was happening i started to mark up the position of the new rad (old one had been removed ) etc. So once that was all done i went to check to see how the draining off was going on, and it was still comming out at a fair few knots. Give it a few more minutes and see how it goes. no differance so i went up into the attic and saw only 1 large tank there, with the boiler and cylinder both venting over it. Thought bloody hell thats really strange, went down and rechecked the cylinder and the pipework and that looked ok ( havent seen a primatic cylinder before ). So ended up having to isolate the main supply to the house and this eventually after a few mins solved the long draining down and i could get on with hanging and piping the rad up. So i was wondering do you think this was a primatci cylinder set up or just a incorrectly piped up system?. It took an absolute age to drain the system so does it also need to drain the cylinder on a primatic system ?.