Reverse Osmosis Water Filter installation kits are available to make potable water.
http://www.amazon.co.uk/iSpring-RCC7AK-U...is+water+filterhttps://www.youtube.com/watch?v=sDhC9XMKLPAI would be quite worried though if the rain water was worse than this;
https://www.youtube.com/watch?v=a6uK3YaloXsNot forgetting your daily medication dose of Fluoride to shift you leftward on the IQ Normal distribution curve of course.