In message , David in
Normandy writes
I want to reduce our metered mains water usage. So I'm
considering using rain water collected from the roof via a
huge water butt outside for flushing the downstairs toilet.
I've heard of others that have done this. I just wondered
what issues I need to think about?

Has anyone else here done this or know of any associated
plumbing diagrams?

Ideally if the butt runs dry then the supply needs to
switch back to mains water (either manually or
automatically).

Presumably the rain water would need to be filtered to
remove any small debris that could block the ballcock
valve?

The rain water must be plumbed in so there is no
possibility of it feeding back into the mains supply.

I need to check for any associated building laws (here in
France).

Advice or suggestions anyone on this project?

Simpler, cheaper and more reliable, if you want to reduce your mains
water usage why not build a composting loo and use none at all? The only
water mine uses is when I rinse the collecting buckets each week after
their contents are added to a compost heap at the end of the garden and
for that I use rain water.

See http://www.jenkinspublishing.com/garden_gallery.html.

The system certainly works in this London suburb. We've been using it
since March/April last year and I've had no complaints from neighbours.
The only briefly malodorous part of the process is the weekly emptying.
Out of consideration for the neighbours I try and ensure I empty early
morning at the weekend. Once the heap is recovered (with organic
material) there's no smell.

The only organisational problem is needing a regular supply of fine
organic plant matter to use as covering material but our garden is
organised on a wildlife-friendly basis so there's plenty of that. I did
ask tree surgeon who lives nearby whether he could supply me with fine
wood chippings on a regular basis (saving him paying to dump them too)
but after initial interest he refused.

If you have any questions do ask...

--
Si