Where to put softener in water system?

[naylorpd]

I live in Azerbaijan, the house has three full bathrooms and has had up to 7 people living there. We store about 5-6 tonnes of water - a necessity because we've had no mains water for the last 2-3 days.

We currently have two plastic tanks but they are impossible to clean, so I am replacing them with a tiled concrete tank, about 5.75m3 (see pics). This is a fairly typical method in Azerbaijan. I'm just at the stage of revamping the pipework.

At the moment the arrangement is:
Mains => Cartridge filter 25u => plastic tanks => pump => RO softener => house

First step is to add a statutory water meter at the inlet and another water meter on the house side with a Flume 2 monitor connected to a phone app for "smart" monitoring.

Next step is to replace the wholly inadequate cartridge filter on the inlet with a proper sand filter that cleans itself.

I was in a shop yesterday looking for this and also talking about the RO softener. They shop guy sprung a bit of a surprise on me by saying that the softener should go before the tank rather than after - so all the stored water is soft rather than just the water we are immediately using.

So his arrangement would be:
Mains => Sand filter => RO softener => tank => pump => house

I'd be grateful for any advice on that...