We had two of those 6 stage, reverse osmosis filters fitted when the house was built around 14 years ago.
The system is fitted inside kitchen units and delivers clean water to the salad sink to wash fruit and veg that is not going to be cooked, and is also connected to the fridge chilled water and ice making system. Normally, these systems come with a 15 litre tank but we went for a 30 litre holding tank instead, as when we have a full house, a lot of drinking water is used and that can come from the salad sink tap if necessary.
Mains water, is also past through a separate, 3 stage particulate filter and used to supply the hot water system for showers, baths and hand washing etc. as no need to fully filter it, as heating the water gets rid of the bugs. A separate, 6 stage system, supplies the cold water supplies to the taps of all the bathrooms.
The wife insisted on fitting a 2 stage particulate filter for the water supply to the washing machine! So I did, to keep her sweet.
Also, father in law fitted a De-Ionising filter to one of the outside taps, so that when he washes his and our car (which he insists on doing on every visit) then he uses the De-Ionised water for the final rinse, which negates the need to wipe the car dry and stops smears and water drop marks.
He is a bit OCD when it comes to clean cars.
He is also the one that decides when the filters need changing on these systems and often turns up with a box of new filters and proceeds to change them. Fine by me and it keeps him happy.
Personally, I would never drink unfiltered mains water in Thailand, but each to his own.
