Filling toilet cistern with rainwater

petec · 3 Sep 2008

I've plumbed an external wallmounted rain waterbutt to my downstairs toilet cistern - with a tee connection to the mains feed, so I can use mains water when not enough rain. I've fitted check valves on both feeds to prevent backflow. However, the cistern doesn't refill from the waterbutt which I think must be to do with the current bottom entry mechanism (a Torbeck type valve I think) only being suitable for high pressure.

Can anyone recommend a bottom entry mechanism which would work for both mains pressure and gravity feed?

Also, what's the difference between a check valve and a double check valve?

Thanks

ChrisR · 3 Sep 2008

No I can't think of one which would work reasonably on both mains and almost zero pressure. You could use a LP one with a pressure reducing valve on themains I suppose. Even then it would fill very slowly from the butt.
A double check valve is exactly that - two in series.
Rain water is category 4, foul water. If you leave it in the cistern a day, it can stink.

powell30 · 3 Sep 2008

Most rain collection systems are pumped (to avoid the very issues you are having).....you could pump it but that seems extreme....unles you connect up other toilets if you have em.

No float valve i know will work well with LP/HP.....as Chris says fit a pressure reducing valve but it all seems over kill....

petec · 3 Sep 2008

Thanks for these helpful replies. What about the Fluidmaster floatvalve that claims to be suitable for LP and HP systems:

www.bes.co.uk/products/120.asp

Do you reckon that could work?
I can live with a slow filling cistern, and the rainwater butts outside smell OK, so I'm not worried about that.

possum_jenkins · 3 Sep 2008

not enough pressure to open check valve perhaps?

would think a check valve before the tee on the cold main woulds suffice

JohnD · 3 Sep 2008

a quiet valve like a Torbeck or Fluidmaster is prone to sediment or grit blockage.

I would have more faith in an old-fashioned type.

There is a thing called an Equilibrium valve that is used in agricultural drinking troughs, but they are shockingly expensive.

To avoid risk of contaminating the mains, I think you ought to use two ball valves, one from each supply, and turn off the one not in use.

this would also solve the variable pressure problem.

tonybhoy · 4 Sep 2008

Thought you were just a householder JohnD

JohnD · 4 Sep 2008

that's me

and an interfering busybody to boot

tonybhoy · 4 Sep 2008

JohnD said:
that's me

and an interfering busybody to boot

Well your advice is spot on for a interfering busybody

BTW,you forgot the 'old'

JohnD · 4 Sep 2008

that's me, old Tony.

petec · 4 Sep 2008

Sorry to interrupt guys...
I thought of the 2 separate entry ball valve solution too. How easy is it to drill an alternative entry hole through a cistern though?

JohnD · 4 Sep 2008

many cisterns already have a hole at each side, for convenient installation

If your cistern is plastic it will be fairly easy. I would use a hole saw.

if it is ceramic it is a job I would avoid.

petec · 4 Sep 2008

Hmm...it's ceramic, with no extra holes.
But I'm not giving up - there MUST be a way of doing it - it's such a simple idea!

possum_jenkins · 4 Sep 2008

You can get ceramic holesaws, but you'd be a brave boy to give that a try, could very easily end up having to replace the cistern.

I do agree that 2 ball valves should be used, however i see no requirement to have more than one check valve, which should be sited on the cold main before the tee ( if you were to go down the one torbeck valve route.)

Seems like a lot of work, but an alternative might be to fit an old style ballcock onto you water butt, say 350 from the bottom. You would DEFINATLY need to fit a nonreturn valve on the inlet however. A bit mad, and very unorthodox, but it would work!

Just a thought!

*prepares to be shot down*

gigz · 5 Sep 2008

Why not just use a bucket for the rainwater, as chris says it'll smell if it sits in the cistern for long. Seems well over the top unless toilet gets used a lot. p.s. instead of teeing them together use two separate feeds with flexi's and an IV on each and alternate between the two when required.

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Filling toilet cistern with rainwater

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