30 Year Old 8mm Microbore Circuit Changes

[PhilT]

Looking to upgrade to 15mm. I thought the 8mm microbore circuit was fed by manifolds, but removing the downstairs ceiling reveals instead a 15mm secondary circuit feeding short 8mm microbore feeds to the upstairs rads, and long 8mm microbore runs dropping down to the ground floor rads (see photo). This should make things easier because I won't have to hunt around for the manifolds, I can just leave the upstairs rad circuit as it is, run two new 22mm pipes dropping down from the primary circuit upstairs, just after the secondary circuit pump in the airing cupboard, and then connect new 15mm runs from the two central 22mm drop downs to the downstairs rads. Any issues with that approach?

[JohnMo]

15 hours ago, PhilT said:

secondary circuit pump

If get rid of all the small bore stuff, can you get rid of the second circulation pump?

[PhilT]

2 hours ago, JohnMo said:

If get rid of all the small bore stuff, can you get rid of the second circulation pump?

Certainly worth considering now I know the top floor is mostly 15mm