For anyone who wants to understand more about this, I can recommend Dryden Pool Academy.
In part it is an advertorial but the amount of data and explanation provided is significant and understandable. I believe @corona might approve of most of the principles included as he has covered several of them in various posts.
It has given us confidence to use a builder for the pool structure and a separate pool specialist for the liner, pipework and equipment . This route appears to offer more options than having all of the work done by a pool supplier.
A very timely post Graeme, I have been writing up some guidance on the technical plant room part of the equation which will follow shortly but I am at a party today and tomorrow.
Not wanting anyone to spend or waste more money or water has led to several developments.
In the past I have always specified a larger pipe size than most pool builders, the reason is not for the filtration cycle as 50mm pipe can usually cope with the vast majority of flow rates on domestic pools. That is almost certainly the mind set of the average pool builder. What the industry training forgets is you generally need 2.5-3 times the flow of water to correctly backwash the filter clean. There simply is not a cat in hells chance of getting that flow through small plumbing even before you consider the 90 degree bends most pool builders use. That means even after backwashing the filter is still dirty further inside than the top of the filter media. As I mentioned on here a while back, using air assisted backwash does a far superior job of cleaning the media be it sand or glass. That does mean you can then use smaller dia pipe (leaving out too many tight 90 degree bends) and use the normal flow rate for filtration as the backwash rate as well and the air will do a lot more cleaning. This saves about 2/3rds of the water you would normally use for backwashing but also the backwash is much more thorough. Thats your treated water you are saving. No one but me is using air assisted backwashing at the moment but on my own filter the results were really good, even deep down silt was released and to achieve that level of clean requires a lot of high flowing water normally and std small plumbing won’t do it. That means over the years poorer and poorer water health as bacteria can colonise and mud ball the sand etc.
We have in Dryden Aqua’s AFM ng the best filtration media, it simply removes far more from the water from dirt to bacteria, all good but if you cannot get that out of the filter to clean it properly you are building up issues for the future.