Hi. Looking to replace my hot water cylinder due to leaking from the top at the immersion flange. Everything seems straightforward except the fact that there are 2 pipes entering the top of the tank at the point of the immersion flange. The standard 'flow to' and 'flow from' the boiler are not used on the tank, so it appears that there is some sort of hot tube being used to heat the water through the immersion flange. Is this a normal set up? If I had to replace the cylinder would I need to continue using this system or could I use the coil within the cylinder. If I need to use the same system what part would I need to attach at the immersion flange. Thanks a lot for looking.