On 20/05/2017 17:44, ChrisK wrote:

No issues with leakage from (now) pressurised 30 year old HW/CH system
(8mm microbore). This was my biggest worry as the water pressure round
here is highish (3 bar).

The mains water supply pressure has no real bearing on the primary
heating side of the boiler - that is pressurised via a filling loop to
typically a bit over 1 bar. It then rises somewhat as the water heats
up. The only bit of a the boiler that will see the full mains pressure
is the secondary heat exchanger that heats the water from the primary
side of the boiler.

There is a noticable issue with HW water flow rate upstairs &
interaction between showers & filling the bath is a bit slow. This is
probably down to re-using the original 15mm pipe work. It would have
been better to have replaced this with 22mm.

Choosing pipe sizes carefully can minimise interactions a bit. Although
a 15mm pipe will likely be able to supply as much hot water as most
combis can produce. Also a smaller pipe will give you less dead leg of
water to drawer off at each use.


--
Cheers,

John.

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