"Terryc" wrote in message
Okay, moving on from grey water to black water, or rather getting "water"
into the cistern.

Does anyone have any practical experience of how much head of water you
need to refill a toilet cistern from a water tank. No Pump.

Sounds to me like a case of simple gravity feed.

All you would need is for outlet from the header tank to be above the point
at which the water comes into the cistern.

But having read the whole of your post, in your case you would need the top
of the water level in your tank to always be above the level of the inlet to
your cistern. Water levels will try to equalise so for as long as the top
of your water is above the top of the inlet to the cistern, the water will
try to keep running into your cistern until the float valve in the cistern
shuts it off so you would need a non return valve if you go this route.

Have you ever seen irrigated land with feeder channels which have a bit of
black polypipe laying over the edge of the mound into the paddock? All the
farmer does to move the water from the irrigation channel to his paddock is
to walk along and shove the pipe into the irrigation channel, allow the pipe
to fill with water, cover the end with his hand (so creating a syphon) and
then drop the pipe into his paddock channel. The water then flows out from
the higher level water channel into his paddock. The cut off is to just
lift the pipe up and drop it back on teh bank of the channel till he next
needs to irrigate.


Looking for head and feed pipe size.

Not hugely critical. If it's a minute pipe (say quarter of an inch) it
would just take a long time to refill the cistern. If it's a 2 inch pipe it
would probably be too big and you might get some splash out of the cistern.
Prolly a half to an inch pipe would be about right.

Are there special low pressure float valves?

Prolly, but we seem to have normal cisterns on our toilets and one pan which
is a proper septic pan (didn't know they existed till the plumber told me
that was what it was when I complained about how bloody ghastly it was)

The standard inlet size to the toilet cistern float valve is about 1/2"
(?metric), however, I figure that if I run the standard 1"/25mm tank
interconnect feed into it, then I will not have to worry about length of
feed and the real question then is what head of water I need.

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.

my plan is to extend the rainwater storage by adding a thin tank on the
side path that can collect (some of) the surplus rainwater from the
overflows. I would also have bottom feed if I can get a suitable
non-return valve.

Given location, it would be feasible to dump the washing machine greywater
into it.

Head would be maintained in dry weather by float value from mains.

I am definitely not moving to electric pump assisted[1]. Maurice the
Lemming has started sending out reassurance letters to pensioners about
the forthcoming changes to NSW electricity, which means bills are going to
sky rocket.


[1] Anyone charging a tank with PV powered pump?