I've had a few properties without mains water and learned how important it is to maintain the system feeding the tank['s] properly to keep the water pure.
It's been amazing how many people aren't aware of the need to drain the system dry when the warm weather starts and the rain stops. Also to do it again within a week or two after summer rain.
When I last drained my house system down it perfectly illustrated what happens very quickly. The first 80% of a lot of water was crystal clear and sweet smelling but the last 20% started to stink until there was a strong smell of hydrogen sulphide, I think that's the gas?
The downpipes are the problem. Most water tanks have the entry level well above the level the downpipes go below the surface so they are full of water up to that level. Mine are plastic and then painted but the light still gets through and that creates bacteria. Some light probably gets through from the open gutter outlet too. If you leave it for several months with no rain it will be a thick green soup that will get flushed into your tank the next time it rains.
Many people never drain it down because they aren't aware or simply don't have a drain cap at the lowest point. Bacteria in the tank water can be bad news, especially for children.
My tank had holes punched through to catch the water on the top and I blanked them all off to stop the light getting in.
If anyone has any good ideas about looking after that vital resource please post them.
