How can "badly installed" domestic copper pipework lead to unsafe levels of {compound of} copper in the water? - consumer reports water filtration vacuums

Now I have seen 2 reports of this on a TV consumer, but does not say exactly what causes it. Reports on the groups building homes in 2 households in the United Kingdom.
Apparently, the developers have to say that, because the residents do not use enough water to keep the pipes (which is of course rejected by the residents). The other reason, because a high level of phosphates in the water reacts with copper, but it looked like the water companies and independent tests proved otherwise. Some residents had to solve all the pipes to replace not say - but why.
Someone really knows what it might be causing the problem, because I love the mystery!
I always thought it was a copper tube for a long time certified safety equipment for the transport of water, and begin in the presence of large amounts of oxygen (run-dry/airlocked for example) oxidation, tubes were?