Parallel two-pipe layout?

[ianniann]

I have inherited (not literally) a two-pipe central heating system which has two branches starting near the boiler which then recombine into a single pair of pipes feeding several more radiators.

I suspect that an original 15mm run around the entire upstairs (with drops to radiators downstairs) was considered inadequate to also feed an extension, so a separate pair of 22mm pipes was run straight through the middle of the house into the extension. It obviously crossed the 15mm pipes and has been joined to them rather than just over/under, not quite in a "cross-roads" but not far off. A section of the original 15mm pipes to either side of the crossing-point has been replaced with 22mm.

Is this common? Normal even? Is it likely to have any downsides? How would you approach balancing? The system appears to work well, but having found horrors like 15' lengths of unsupported pipework, 22mm pipes in 15mm joist notches, 2x22mm pipes jammed through the same notch as hot and cold water pipes, floorboards unsupported on one side because the notch is too wide, and floorboards (across a busy doorway) literally just resting on the pipes, I'm worried about what other things might have been bodged.

 

[muggles]

I think some photos are required here...no idea what you're on about I'm afraid!

 

[ianniann]

I think some photos are required here...no idea what you're on about I'm afraid!

Well my drone's out of commission and the pipework is under various floorbaoards, wardrobes, and even a shower, so I'll try to describe it differently.

Ignoring the twists and turns of the real world layout, the pipework comes down to: about 3m of 22mm dual-pipe from the boiler. It splits into 15mm and 22mm dual-pipes which each run about 4m. Then they join together into 22mm dual-pipes for about 1m. Then that splits into 22mm and 15mm for the final runs to more radiators.