Who Has A Berkefeld?

[Chaos25]

Hi everyone .I have been reading this site for a while now and have picked up some really useful hints, tips and info.
Myself and a couple of others are renting some woods from an absent landlord which we use for allotments teaching the kids bushcraft and we are curently using it to test preps .We have built in a composting toilet and are just finishing a yurt and for fun for the kids we have built large treehouses with rope walks between.We have built an amptitheatre with a fire pit.
We seem to have one problem ,as we live only a few yard from the area we carry water up,the thing is even though we have no ground water we do get a lot of run off which we can store, If I can help it I dont want to go to the expense of buying a water filter system if we can use the run off stored in water butts and instead use the system described by northern raider. I have food grade plastic buckets and the putting of them together looks simple enough, just need to know if this would make it drinkable though.
I have spoken to some companies about this, but the just seem to want to sell lots of expensive additional extras.
I would be over the moon to receive any advice.
Many thanks Chaos25