Flushing a toilet with rain water

DPinBucks

First thinking aloud point:

Isn't the whole point about the hosepipe ban that we're moving into drought conditions?  In that case, where's the water coming from to fill the butt?

1 flush = approx 8 litres.  That's 100 flushes per tank-full.  One good rain shower will fill it OK, but how many times do you use the toilet?  Say 5 times a day.  That needs a rain shower every 3 weeks or so.

First conclusion: you should be OK on that score.

Second thinking aloud point: you're not actually saving anything significant.  We all flush our toilets, drink and water our gardens with rainwater anyway.  That's where the water companies get it.  Unless you live near the coast, your tapwater has probably been used by at least one household already, and, plus your rainwater, will probably be used by at least one more before it reaches the sea.  All you're really saving is the cost to the water company of treating your toilet water (which is fair enough, but is a small fraction of their ongoing infrastructural costs), and yourself about 1.5p per flush, or say £27 a year.

Second conclusion: that's a bigger saving than I thought.  Payback in 10 years (those large butts are about £300, I think).

To make the maximum use of the water butt, you'd need to empty it completely between rainshowers.  Flushing the toilet might not do that.  What about other uses?  The hosepipe ban does not prohibit using a hose attached to a water butt, so you could use it with a pressure hose to water the garden.

Flipper

The 800L tank is for watering the garden. We have a large garden with a lot of plants and shrubs so would use this with a hosepipe and some form of pump.

The toilet flushing was a secondary thought as the tank would be situated very close to the outside wall of the downstairs lav.

RMCF

Don't some people put a brick in their cistern to bring in less water with every fill?

Then again, perhaps it needs that extra water sometimes to get rid of the odd , ahem, extra heavy load!!

Treadstone

A modern dual flush cistern only uses about 3 litres on the small flush.

Wild Weasel

Yes, but they're so rubbish they have to be flushed several times to do the work of one old toilet.

RMCF

and we all know what this means.

F L O A T E R S !!!!

Tfish

well this thread turned ti dung quickly!

Anyway......... OP did you make a serious decision regarding this?

We will all be metered in the near future, less than 5 years the companys hope so this is of interest of all.

Flipper

No decision yet, project is on hold due to lack of funds.

Wild Weasel

I reckon it costs about 4p to flush the loo, so it does seem mad to allow all that free rain water to literally go down the drain. Especially as toilets use drinking water that's been treated and pumped for miles to get to you.

IronGiant

I think that's a bit high, but it can still amount to a lot over the year: see here:

Rainwater Harvesting Toilet Flush calculator

He reckons about £50 a year could be saved.