Mixed bore pipework in CH system

[wonderdog]

Hi all,

The central heating pipework in my house is mostly in 15mm but the final spur to each radiator is in small bore (10mm or 7mm) - typically for the last 5' or so of pipe running from a stepdown T or elbow joint. I'm pretty certain there's no manifold, so not a true microbore system. Firstly I'm wondering if anyone has any ideas why it might have been done this way.

I had the boiler replaced about 5 years ago with a Potterton Suprima 100L and at the same time the heating guy installed several new rads on normal 15mm pipework. Because we've had some problems with corrosion, (pump probs because it was full of bits of rusted metal and other cack), I'm thinking of replacing all the small bore pipework, (and old rads if necessary), before next winter. My question is am I likely to cause more problems with the wider bore pipes, and will the boiler be powerful enough for the job.

Boiler is on 1st floor, fully pumped, open vented system. The area is about 2000 sq ft, over 3 floors, and there are 14 rads, (some quite large), and 2 towel rails.

Any ideas gratefully received - thanks

 

[twgas]

if your corrosion problems started when the new boiler was fitted it may be an issue with cold feed/open vent configuration.
boiler should be ample for your system.
are the new rads additions or replacements?

 

[wonderdog]

Hi twgas - thanks for your reply.

The boiler has been fine and the only problems we had were just this year, where the pump started making unholy racket, which was when we isolated it, opened it up and found all the bits of rust and stuff in it. We cleaned it out, and it's been behaving quietly ever since - but I guess the problem will be accumulative over time. (I should mention also that we're in very hard water area and to my knowledge no inhibitor has been used in the last 5 years at least. Water from rads is pretty grim - black, grimy, etc.) The new rads were mainly replacements.

Thanks for reassurance about the boiler capacity. So - given that the boiler is strong enough - I'm thinking regularise the pipework, flush the whole thing through, dose it with inhibitor, get the system balanced properly, and it should repay me with a few more years service.[/i]

 

[swbjackson]

If you're getting flakes of metal fit a magnaclean as well because a flush may not get them all out.

 

[wonderdog]

Hi swbjackson - thanks for suggestion - I think that with the magnaclean too I'll have done just about everything poss to nurse another few years out of it all. Thanks for advice/suggestions all.