have a similar system - but smaller consists of 4 rainwater butts interconnected - 2 inside are float valved - then a small 12 volt pump and non return valve ( local camping shop ) - straight to the cistern of the loo ( valved so i can switch over as needs be ) - all available rain from roof diverted to this - and for one person lasts very well
run my pump from solar charged ex mobility scooter gel batteries ( they may be a bit weak to run a scoot - but OK for most things and hold charge fine )
whatever - saves me a fair amount over the year - dependent on rainfall of course
don't bother with any filtering - and just flush /clean system once a year during summer ( whenever we get those 2 days

)
would love some bigger tanks - but cant get em down here and transport costs too much from the midlands - ho hum
( less of course any of you know of a cheap source near Plymouth ( UK ) ??
