Microbore for DHW

[Toby Cambray]

Some sustianability-orientated designers are evangelical about the benefits of microbore for DHW, and on the face of it, it does seem there are some 'practical' as well as energy benefits - speed of hot delivery being a big one.

I'm interested in specifying microbore but have concerns about noise, and would like some more detailed guidance on general design but am struggling to find any. Can anyone point me in the direction of guidance on this topic as CIBSE, AECB and the DCLG do not appear to offer any...

[Matthew Thompson]

There is some outline guidance in the CarbonLite Water Standards but I'd also welcome some more detailed information.

[Mark Siddall]

I spoke to Alan Clarke about this a short time ago. He is not aware of any noise issues in the systems that he has designed. I found that:

* CIBSE Guidance does suggest that PEX will is quieter than copper.
* Large pressure drops across valves can be the cause noise. AECB guidance suggests one pressure reduction valve at the point where the main comes into the house if the pmains ressure is greater than 3 bar so this should help limit the pressure differences in other locations (to play safe you may locate the value, if required, in a non-habitable room).
* CIBSE guidance can be used to calculate the pressure drop within pipework so that it may be limited to less than 1 bar (as recomended by AECB guidance).
* For comfort wait times from cause by the pipework should be limited to less than 5 seconds (see AECB standards). 

Obviously AECB Water standards do offer some insight/guidance (though they do not mention noise in a specific fashion).
http://www.aecb.net/PDFs/waterstandards/1503_AECB_Water_Vol_1_V3.pdf
http://www.aecb.net/PDFs/waterstandards/The_AECB_Water_Vol_2_V3.pdf

HTH,
Mark