I finally gave in and got myself a water filter. It's easy and cheap to buy drinking water in bulk in Thailand, it comes in big 25 liter bottles, it costs 12 baht, about 40 cents. It's made just down the road in a factory using the latest reverse-osmosis process, and it's absolutely no hassle to buy.
So why buy an expensive filtering system? Honestly I'm not really sure why I did it! It's not like I have to purify water anymore. The days of growing up on the farm, drinking well water have gone.
I think it's because it's handy to have it on tap. For rinsing vegetables and fruit, its quite nice to be able to turn a tap and put them under running water.
I opted for a 5 stage, reverse osmosis purifier after studying the web.
A sediment filter to take out the large particles over 5 microns.
A carbon filter to remove chemical impurities like chlorine, organic material, and to improve color and taste.
An ion-exchange resin filter which removes dissolved salts.
Then the reverse osmosis filter, to remove things larger than 0.0001 microns.
This is where it gets complicated, that filter is slow and removes things like bacteria from the water, so it needs a tank. Mine comes with a 12 litre tank, and it takes an initial 30 minutes to fill that tank.
After the pressure tank, another carbon filter to remove anything introduced in the filtering, and out of a tap it flows!
This system cost me 8200 baht, $275 or so, it's not cheap, but does include installation. It comes with everything, including the tap, and the installer fitted a power socket for it. An automatic pump drives the system.
But so many pipes, it was inevitable there would be problems with it, and sure enough the next day there was a pool of water under the sink. I felt around all the joints bu couldn't find the problem, time to call in the fitter.
So, minor problem done, it all seems to work.
The official maintenance for the filters is: Sediment and RO membrane filter every 6 months, and the other filters every year. But I'm a lite user, and the water here is very clean, so I don't plan on changing it more than once a year.
It's more about piece of mind than actually filtering!