You will need to find out where your water supply comes from too - is it from "your" site such as a river, dam, well or bore or rainwater tank? - and are you legally entitled to the water?
Or is it from the local Council or water authority pipe out in the street?.
If it is from Council/Water Authority - write to them and get their statement of their water quality analysis they supply and where that comes from - bore/well/river/dam.
If it is from "your own" site - you need to get some water analysis done by qualified labs - and you need to tell them what standard of water you need - or as the others explained - "What do you intend it be used for?"
When you say purified unfortunately that means very little - you need to know what parameters are important for the use you intend - purify usually means "safe to drink" - i.e. "I won't get sick" But if it is from a bore it could be contaminated or have say naturally occurring arsenic for example!" - some people would see slightly salty or hard water as impure - but it may be quite safe to drink but will clog up tour kettle,say.
Its usually not that scary bur seriously if you are responsible for this supply you owe it to your client/friend or yourself to get some sound advice before you start buying water treatment equipment or advertised devices
