Moving cold feed and expansion

hello diy22 and welcome, the blockage will be on the first tee down the cold feed, So if that tee is easy to get at, just cut that out and it will fill again, If you can't get to it, another good way is to fit a filling loop in the cylinder cupboard, connect a pipe from the cold main to the boiler vent, put a valve on it so it can only fill as you supervise it, block the vent with a conex cap and fill the system, when its full take the cap off the vent

can you post some pics of your airing cupboard please

This is what I plan to do. The green is the new part of the system.



Should it work if I block off the current feed and expansion pipes in the loft?

That is the loop going into the hot water tank so is after the pump and diverter. Does that matter?

How would I route the feed and return lines?

Thank you for your help.

Perfect. Thanks very much.

How would I have the pipes set up? 

This is how it is at the moment.

So cut off the current cold feed in the loft and put an automatic vent.

Cut off the current expansion vent in the loft and put another automatic vent.

Extend the 15mm (currently auto vent) and connect that into the loft tank as the new cold feed.

Add a new 22mm pipe to the loft tank as the new expansion vent.

thats about right yea, they don't need to be auto vents, in fact manuals are better because they wont drag air in, There's not much room but it looks to me easier than working near the pump and there does not look to be much room to put tees in,

another option that I would do as my first thought, take the auto vent off in the existing cyliner flow, and fit a ballofix or stoptap, then connect it to the cold mains, this might push the blockage out, put even if it does not, it will fill the system because it has two routes, flow and return,

edit,, forgot to say, blank off the cold feed and vent cos it might overflow from the top of the tank,