Expansion tank problems

[jiffter]

PLEASE HELP URGENT!
Removed a hot water cylinder today and thought i'd got all the various pipes mapped out but i have a problem with one remaining pipe. I'd written on it " feed to expansion tank" but not the mains feed that operates the ball ball cock. The pipe came from the hot water cylinder area and fixed on the bottom of the expansion tank. Does this pipe key into the primary boiler inlet or am i talking rubbish? Either way i'm desperate to get it finished as the the family arrive back tomorrow.
Any help very appreciated.

 

[Resolute]

Can you post a couple of pics? Also might help if you list what pipes you do have.

 

[jiffter]

I'm sorry i cant send pics cause im back at my parents house now. The cylinder has been removed to allow more room in the bathroom and a horizontal hot water cylinder and coffin tank has been sited in the loft. The original hot water cylinder had the normal primary and return pipes.The return pipe had a vented pipe coming from it into the expansion tank. A cold water feed from the water tank was fed into the cylinder and a hot water feed with a vented pipe back into the cold water tank. I should have taken some pictures before i removed the tank but didnt. I really dont know where the offending pipe should go and im now wondering if the expansion tank needs to be elevated above the horizontal hot water cylinder?

 

[WHPES]

The F&E tank obviously needs to be above the DHW cylinder or how can you fill the coil with water?

Make sure your swan neck vent pipe is sufficiently high enough above the water level. Pay attention to miniumum distances and clearances re Building Regulations requirements

 

[royston]

Luv to see some pics !