Why do so many use booster pumps if it's illegal?
Water companies have to provide a minimum of 1bar pressure. A booster pump won't increase the mains pressure. But if you buy one with a small holding tank it will take the water from there and push it through your RO at a greater pressure, whilst the flow from your mains remains the same. In simple terms...
This is not true , if you have enough flow then a pump will boost the pressure , as mine does .
Tecnically you are not supposed to increase the flow directly from the mains by more than 12 litres per min .
There is a minimum standard for flow and pressure from the mains but the standards are low .
I had southern water round to check mine and the pressure was just above minimum and flow was slightly below , they have increased the flow since and as a result my pump boosts about 10psi more than it did as it is no longer over running the supply and cavitating.