Ok. No red lime. So, there is no loose Calcium Oxide. Is it the more stable caSO4 or CaCl (or something else) that makes the water very hard?

More tests to find a good way to –treat– this water. Boil some (say 1 litre) water. Catch some steam and let it condenses into water droplets. Catch the droplets –of pure water– to taste when it cool down. Now pour the boiled water through a piece of cloth (filter) to see if we have as much sediment as (1 litre) unboiled water.

I remember vaguely about a blog on Gotoknow by Dr Tavich Chitsomboon on a simple water filtering gadget (will look and post the url). I also know a friend who has been producing (more expensive) “high-pressure water filtering” gadget but i Am not able to talk to him yet.

There are many webpages that talk about hard water. I looked at this==วิธีการแก้ไขปัญหาน้ำกระด้างถาวร น้ำกระด้างชั่วคราว แบบได้ผลจริง==http://sk.nfe.go.th/hatyai05/?name=knowledge&file=readknowledge&id=87—-เครื่องกรองน้ำดื่มช่วยน้ำท่วม - คนถางทาง - https://www.gotoknow.org/posts/469107