I installed this system in 2012/13 with some help from Dave Dwyer and a mate of his.
The workshop(garage) roof was ideal because if any leakage of greywater occurred on the roof it would not contaminate the potable water collecting system on the main roof.
The sump 1 was firstly installed to collect greywater from the washing machine, shower and washbasin (en suite) and pump it up to a 150ø x 6m long OPVC holding tank on the ridge to provide gravity feed by time controlled shut off valve to allow surges of GW for max. exposure to UV. This was then collected in a gutter at the bottom of the tray and piped by gravity to the vertical cylinder next to the 400L water tank. This semi-purified water was then pumped by pressure operated pump to the WC cistern. While the hydraulics worked the final water was still a bit too smelly and not clean enough. The UV panel was glazed to encourage condensation to form and trickle down to a separate gutter at the bottom . This also worked as a trial but needed to be a bigger output. Obviously, more exposure to UV was required but by 2013/14 I was too wobbly on my feet to feel safe on the roof so under orders from the doctor (and Maxine) I had to abandon the project. I had it stripped off the roof as it was a bit of an eyesore.
Nevertheless I learned something – I was on the right track, but someone else will have to take it on, if they can make the opportunity come their way. The UV system will work but it needs more time and less depth of water to penetrate = bigger panel area. If this could be cracked economically I feel sure a house could be a water neutral unit – at last count we were 82% self sufficient. Beaten by time and health.
For all my calculations see a manilla folder in my wardrobe shelves or in the filing cabinet or on the computer.