Replaced cylinder but header tank won't drain

[Alderbury2]

I know I shouldn't have tried this without a safety net......

Replaced the badly leaking direct cylinder.

When I drained the radiators flow stopped but the header tank for hot water remained full. So I went ahead as radiator flow from rad downstairs stopped after about 30 mins

Old Tank emptied ok, new one in no probs.

All taps work. Hot is flowing but cold, see below.

Boiler fires up for 1 minute, the pump in the airing cupboard with new cylinder attached get hot and motors, before boiler cuts out.

I re drained all radiators. Same problem of header tank stays full, also ground floor rads remain full despite the one with hose to drain now empty.
I opened all upstairs bleed valves. There is still water in the system some how.

Any ideas what I may have cocked up when replacing hot water cyl or why hot water heating side won't drain?

 

[dcawkwell]

Sounds like your a bit confused.

I think you have an indirect hot water tank. Central heating header tank in the loft and hot water header tank in the loft.

Ok so you've replace the tank and now got water flowing through the tank.

It sounds as if you haven't managed to fill the central heating. Usual problem here is the filling pipe from the header tank is blocked.

Attach a hose to an outside pipe and to the drain valve with the aid of a jubilee clip. Then fill the system with a slow flow of mains pressure until
the header tank starts to overflow. That should sort it out.

 

[MrTherm]

My sneaky suspicions -->

Could be a *Primatic* cylinder incorrectly replaced with a direct or even an indirect cylinder?

more info and clarification needed, or photos of old cylinder showing side vent screw etc'

for ref:
a Primatic cylinder can be fed cold water to both outer and inner cylinders from one large cold water cistern (separated by air bubble in inner cylinder dome)

 

[JohnD]

the header tank for hot water remained full.

what size is this tank? how many tanks have you got?

it sounds to me like the feed and expansion pipe, from the F&E tank in the loft, which runs down and joins the main circulating pipes, usually near the cylinder, is blocked with hardened sludge and sediment. This would explain why the tank did not empty when you drained the rads. It will also prevent the rads refilling. When you try to bleed the upstairs rads, what comes out?

have you got a strong magnet? Hold it against the F&E pipe where it tees onto the main pipes. Is it attracted?

Photos of the pipework would be a great help. What colour is the cylinder, and what is printed on it?

 

[MrTherm]

sorry JohnD, posted about same time.

 

[Blagard]

Attach a hose to an outside pipe and to the drain valve with the aid of a jubilee clip. Then fill the system with a slow flow of mains pressure until
the header tank starts to overflow. That should sort it out.

You would need to plug the expansion pipe for that to clear the fill (feed) pipe!

Edit: The OP should really write again as terms are beings mixed up. i.e. Refers to replacing a leaking cylinder and then talks about replacing a tank!

ignore the reference to Primatic as you would never have been able to drain off something with the a header tank still full of water. - A primatic system uses just one tank!