On 25 Jan 2018 16:57:12 GMT, Tim+ wrote:


snip

Or anything that substantially reduces or restricts the flow,
especially where it's not easy to access / service.

Actually, I think it’s the flow restriction and probable inadequate
corrosion inhibitor that combine to lead to the blockages. I’ve probably
been a little unfair to the hoses in that nothing appears to have gone
wrong with the rubber and there’s no corrosion of any hose components that
I can see.

Ok ...

When you have a 15mm pipe that is constricted to 6mm, then opens up to
about 12mm before going through another 6mm constriction, I think you
probably have the perfect device to trap any circulating crud.

Quite, and whilst the hoses themselves may not have actually failed as
such, (as you say) the 'design' seems to be party to there being an
issue in the first place?

snip

On Mums system the first 'restriction' in the system is the heat
exchanger so after some bathroom reworks we felt some scale had broken
free (and there wasn't much in general) and was sitting in the heat
exchanger. We took it out but it seemed clear enough (considering how
old it is) but after putting it all back together it seemed ok again.
shrug

Cheers, T i m