Locating a Pressure Booster Pump

Haven't you answered your own question?

Put the RO filter after the pump, before the houses.

"...graduated to deliver 7 bar."

In your house? Do you need to spray water the roof with the lawn sprinkler?

RO filters operate at fairly high pressures.

7 bar may not be too much.

You only need to RO the water used for potable purposes. The raw water is fine for flushing toilets, which can be a major part of water used domestically. The toilet should gravity fill from the feed from the tank if you use an old float system.

The booster pump feeds the RO which will fill a pressure tank. From there it goes to the hot water heater and the other potable water taps.

...and don't operate the RO too fiercely. >60ppm of calcium in the water is vital to achieve palatability and to reduce the water's tendency to be agressive with fixtures and fittings downstream. Blending with raw water may be an option, as may be re-hardening downstream of an RO.

Interesting that there is no mention of cartridge depth filtration nor carbon cartridges upstream, nor UV sterilisation as the final step. One wonders what the raw water analysis looks like.

I have more questions than answers, for instance, "why put the storage tank up high", I would have buried it so that it would stay at a constant temp, you say your going to use a pump to deliver to the house so it won't matter if the tank is below ground, you say," your going to use a 7bar pump", I say "why so high when a 3-4 bar would be more than enough", a closed high pressure hot water cylinder normally has a max 5 bar pressure, if your worried about flow capacity then use a high flow pump but with 3-4 bar I think you will have more than enough flow. On my own house I've a maximum of 3 bar (because thats whats delivered by the water company), the supply is split into drinking water and domestic supply,the domestic supply is then put through an equalizer valve so the cold feed to the hot cylinder and the domestic cold are at the same pressure, we have 2½ bathrooms and have never run short of pressure,I also have a water softener on the domestic side, a 410 liter high pressure cylinder & a condenser boiler & with people using both bath rooms I have never run out of hot or cold water.

Bazzer.

The "high" was for gravity feed but then the pressure was not enough to supply the hot water cylinder, hence I had to buy the pump later. The 7 bar is the maximum indicated on the pump itself by the manufacturer, whether it will achieve this much in practice is still to be determined

If 7 bar is the maximum pressure for the pump, you'll not get anywhere close to that.

You should look at the pump curve to determine flow and pressure.

Look closely too at the pressure rating of everything downstream. If any item is weaker than the pump maximum outlet pressure, expect it to fail spectacularly; in particular, that hot water cylinder, because in the UK it's 0.5barg max!