"The Natural Philosopher" wrote in message
...
Anita Palley wrote:
On 13 Jul, 13:24, olo wrote:
Hi folks,

need your advice on pipe size - what would you recommend (15mm or
22mm) as a supply (cold) to and flow (hot) from combi boiler to taps?
Boiler can produce 14 ltrs/min so one would think that 15mm pipe is
enough. However there are opinions that 22mm is preferred because
boiler will get priority in getting cold water.

thanks for any info,

On my combi the tail at the bottom of the boiler for taking cold water
is 15mm, and so I guess is the pipework within the boiler. In this
case I can't see any benefit it having 22mm pipe from the main, or am
I missing something?


flow rate is not limited exactly by pipe bore alone, its a function of
pressure, length and bore.

So if you want flow rates to be high, use large bore wherever you can.

The downside is the space it tales up, the heat that may be locked inside
it and lost, and the cost.

I tend to think in terms of 22mm almost everywhere, these days.


Also hot water takes longer to come through a 22mm pipe - the volume of the
pipe is proportional to the square of the radius (or diameter), the flow
rate to some lesser power. This means it's brill once the hot water has
arrived, as the flow is larger, but there's a longer period flushing out the
cold.


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)