Today was a wet day so we decided to work on another task. Something that we could have done much later but we felt that we could make use of it right now, and that is a unit to filter and sterilise the rain water we have stored under our garage. It has been filling up ever since we finished doing the gutters and collecting the water coming off the slate covered roof.
We have a entrance into the tank in the back room of the garage, hidden under the floor and after opening the access, we could see that our tank is indeed filled up with clean looking water. The depth of the tank is 1200mm and the access tube was 800mm deep for a total of 2m. We had previously installed a level detector system down one side (it has 7 levels to give us some idea of how much water we got) as well as temperature probe. The capacity of this underground tank is about 15,000 litres (equivalent to about 75 water butts!!).
So we installed a submerged pump, connected a fat pipe to the pump and brought it up to join with a standard 22mm domestic water pipe. Then connected the mains electricity and did a quick test to make sure the pump was working. Yes Indeed It Was, it gushed out into our kitchen sink rather too quickly!
So that end of things was ok and set ready so shutting the man-hole up and putting back the false floor covering, we got on with making up the module that will filter the rain water through several different types of filters and then passes through a sterilising unit too. We fixed each unit to a sheet of OSB board, joined each unit together and then fitted the long stainless steel sterilising unit along the top of the board.
So the water comes in on the left side, enters the particulates filter removing particles right down to 1micron in size, then passes through a flow measuring sensor then enters the second filter that has activated carbon to remove chemicals like chlorine, pesticides and other chemicals that have blown onto the roofs. The output of this unit is then fed up and enters into the long stainless steel and glass chamber that has very short wavelength Ultraviolet (UVC electromagnetic radiation) light shining into the flowing water, to deactivate viruses and kill bacteria, before exiting the module on the right side. There is a flow rate valve to make sure the water is flowing nice and slowly to give the filters but most especially the UV sterilisation process to work at maximum effect.
The whole panel was installed under the counter in the kitchen and plumbed in. We did a quick test of the pump and filters and they seem to be working. We just need to make a control box to turn the UV light and pump on when the header tank needs water.