"Terryc" wrote in message
...

Since Sydney seems to have gone back to wettish weather and the tanks are
mostly full, I figure it is now time to get serious about using rainwater
(and grey water?) for toilet flushing.

you don't want to use grey water for toilet flushing unless you make it so
that the excess (which there will be, unless you have a household of at
least 10 incontinents ;-) goes on the garden.

the law says grey water should only be stored for 24 hours. i believe some
systems with uv treatment & filtering & whatnot can be stored longer, but i
assure you that without any treatment you cannot keep it more than 24 hours,
& you won't want to, either ;-). we put shower water into the washing
machine, & on those days when i just don't get to the washing when i wanted
to, it starts to smell in warm weather. if no washing is going to be
happening within a day, i don't put it in the machine cos it's just a bad
idea :-) (how shower water or indeed washing machine water gets germy to the
point you can smell it, i can't really work out, but there you have it - and
that is reflected in the guidelines).

some spanky modern systems will incorporate all the grey water together for
the garden and the toilets, in which case you need to release it (or have it
on an automatic setting) to go through before it's too old, however, i
gather you wanted to rig up a system yourself. you could do so i'm sure, i'm
just emphasising that you need to be very aware of how long you're storing
grey water, & that it needs to be released (onto the garden) in time to
avoid problems. some systems release it into the wastewater, but that seems
an odd choice when you could put it on the garden instead.
good luck!
kylie