Hissing/white noise through water pipes

[Ouch77]

Hi all,
Bit of a speculative ramble, keen for opinions and experiences.
Moved into house a couple of years ago with intention to extend and renovate. house is old and bodged.

The plumbing is very noisy when running- what i'd call 'white noise' This isn't the thunk of pipe-hammer, this is a steady white-noise hissing that is proportional to the rate of flow.

System pressure in the area is good to high (it gave next door some leaky issues).

As I go through the renovation process, the time will come in which the plumbing will be overhauled/replaced/upgraded. When designing what are some of the best practices to maximise flow yet reduce noise. I'm thinking:

1. Increase pipe diameter where possible (it's all 15mm copper at the moment for DHW/DCW) to reduce the flow speed
2. bend pipes where there's space rather than fit an elbow.
3. Select valves and fittings for noise, so ball rather than gate perhaps?
4. Ensure pipework is well secured to avoid water hammer.

As an aside, the heating system does a lot of clicking and clunking as it heats/cools - I'm guessing this is due to the copper pipes expanding and contracting - any suggestions to minimize this when the heating system is overhauled/redesigned?

 

[Madrab]

It's down to water velocity - the flow through your pipework is exceeded design standards of an absolute max of 2ms, which is the top limit of what it should be to minimise friction and turbulence.

If you want to do it properly then you need to do adequate pipe size calculations.

As per your questions -

1 - Yes - this will reduce water velocity and maximise flow
2 - Yes - anywhere you can reduce tight bends will minimise friction and reduce turbulence
3 - Valves aren't as much as an issue but anywhere you can adopt full bore valves will again maximise flow
4 - Always have pipework properly secured and lagged where possible
5 - If your water pressure is above 3 bar then fit a good quality pressure reducing valve to protect your systems

Your heating system - yes - usually down to expansion and contraction where the pipework isn't secured/lagged and/or the pipework touch each other and/or the fabric of the house.