Rainwater harvesting

Hi All
With the introduction of water charges in ireland coming i decided to get ahead and installed a 200 ltr tank to collect rainwater from the gutter for
watering the plants and stuff
I mounted the tank on two aerial mast brackets anchored on an external wall as there was no room to put it down the side of the bungalow its almost up at the gutter as i also did not want to loose any room on the decking
then i had an idea that as its up higher than the bathroom could i use water from this tank to flush the loo
can i just put two ball valves onto the pipe work of the existing feed into the cistern and just switch off the mains when using the rainwater
would i need to filter the water back into the cistern or will any bacteria in the rainwater contaminate the the tanked water supply from the attic although this is not drinking water we would use it for brushing our teeth & shower & that
any advice most welcome
thanks

Don't know Water Regs in Ireland but would have thought they would be very similar to English, I think you have answered your own question about contaminated rain water getting back into the house system.
All cold water drawn from a protected cistern (which is one which has close fitting lid, filtered vent & O/F etc) is classed as drinking water. The protection afforded by the float valves (ball valves) either in the WC cistern or in the main storage cistern (AG) would only give protection against back flow (contamination) to fluid category 3. THe RW water would be classed a category 5 so would need a minimum air gap type AA or AB basically this means that the water inlet from the house supply would have to enter the cisterns above the overspill level.
Hope this make some sense, basically don't do it. What are you going to do in the winter when it freezes?

Chris
Many thanks for your reply
Asi did not get a flood of replys saying dont do that you will poison the whole family i went ahead and installed a check valve on the pipework just below the cistern i also installed 2 ball lever valves one on the tanked water and one on the rainwater in such a way that you cant turn on the rain water without first shutting off the tanked water as the lever will be in the way
i had looked at the filling loop from the central heating and thought if the manky water in the heating is only seperated from the mains by a ball valve then the risk cant be overwhelming
I know that all plumbers will tell you the filling loop is supposed to be disconnected from the water after its filled
looking at most installations here most plumbers seem to leave them conneced
since you suggest an air gap i have googled back flow & cross contamination protection valves and the prices were astronomical
i will however bow to to your knowledge on this and disconnect it till i can find a suitable valve to entirely seperate the 2 water supplys
do you know of such a valve that could be installed in line between the tank water and rain water

on a side note not worried about freezing as i can just drain the water from the water butt when the weather is bad

again thanksk for your reply
Cheers

Hi gerinemo
I have some bad news, I am afraid, regarding your backflow problem with the re-cycled rain water. Although as you say some central heating systems can contain some "manky" old water in them it is only classed as category 3 water which may not be very nice & lead to an upset tummy but will not kill you, as most plumbers will testifier to, having accidentally taken a mouth full while siphoning / draining down. (that is why it only has a double check valve & removable filling loop as protection). Because of the biological risks associate with storing & using RW it would be, as i said, category 5 for which there is no mechanical backflow device!!! You can only use an air gap (AA or AB) which would offer this protection. RW is normally stored underground where it is both cool & dark to reduce the risk of growth. I would be worried about the water being heated by the sun (even in sunny Ireland there must be a good chance that it would be above 25degC) & so there would be a real risk of Legionella to you & your family.
Please seek professorial advice before you continue.
Regards CW

Will abandon it so
many thanks for your advice :-)

Can you pipe it up to flush the toilet only? With a ball valve from the main with the correct air gap to top up when its not rained enough (unlikley in Ireland!)

Very difficult to create an AA or AB air gap. AA discharges from a float valve with a minimum air gap of 20mm (depending on the size of the supply) before the overspill level of the cistern, so not really possible with a protected cistern. The AB has a long weir overflow slot which is screened & normally shielded from the light but difficult to do domestically as you need something the catch any water that could overflow.
So in answer to your question sambotc no I cant think of a way to do it.

I have another 250L water tank complete with ball cock
if i was to put that into the attic and run a supply from the origional water tank into it and pipe that one only to the loo
(easy enough as its a bungalow and the hot press is right beside the bathroom drop the pipe down in there and straight into the cistern )
the ballcock in the 2nd tank should give me an air gap ?
what do you think

Hi
as long as you can achieve a class AA or AB air gap it would be fine.

rainwater.jpg

how about something like this? Just looked in my water regs book for the first time since doing the course....

Sam's one is fine but just to confirm that this is an AA air gap with water outlet above overspill level but that would not have to stop you installing a circular overflow/ warning pipe to protect the dwelling from water damage if float valve overflowed. just a problem to alter / extend the float arm to give the correct water level.
P.S. I take it that the larger cistern is the WC cistern & the red pipe is the flush pipe / supply to the pan?

No I was thinking 2 tanks in the loft Chris,but having read what you've just said, I over complicated it somewhat as like you say you could just have an overflow pipe and the AA air break on the one!

WaterButt.jpgThanks for all your help lads going to put the other tank in the loft and run a new pipe to the loo
Cheers :-)

I'd like to add a bit of an overview on the direct versusgravity aspect of RWH (rainwater harvesting) and suggest one possiblealternative approach to the mains back up question.

I think that using a gravity tank in the loft to cater for mains back up hasconsiderable disadvantages:
1) any work in the loft is time consuming and awkward;
2) cost of tank, connectors, pipework and proper insulation for tank and pipes;
3) a backward step in terms of placing pipes where frost may be a risk;
4) potential for water to become warm in hot weather
5) BIGGEST DOWNSIDE is that most modern WCs have small cisterns fitted withinlet valves requiring a high pressure supply.
The cisterns I have are too small to accept a low pressure ballcock, even withan adjustable arm and shorter type of ball.
6) Even if a ballcock did fit it is a slower and noisier device than a modernHP Torbeck type valve.
7) As far as I am aware it is necessary to braze two ballcock arms together togive the long reach for the mains back up supply ballcock in the loft tank.

So all in all my view is that GRAVITY is BEST AVOIDED.

If one is going to use a DIRECT FEED from a pressure sensitive pump to WCs,outside taps and possibly the washing machine then the usual approach to amains back-up would be to supply mains water, either manually or using anautomated system, to the main RWH tank, usually underground.

Another approach, that has occurred to me, is as follows:-

Have an arrangement, whereby the supply pipes to the WCs, (at some high upcentralised point in the house) could be connected by a filling loop withdouble check valve EITHER to the RWH supply OR the mains supply.

The pipes would be so positioned that the loop could not physically join theRWH and mains pipes.

In effect one would be converting the WC flushing from mains to RWH and backwith the changing seasons.

So would WRAS regard the connection of mains water to WCs that had previouslyused RW as a connection to a RWH system?
In other words, would they still insist on a class AA or AB air gap?

Your thoughts on this or a non-ballcock inlet valve that works at LP would beappreciated.

The lesson I have learned is that is vital to resolve all these issues inadvance so that all required pipes and cabling are correctly installed.

old thread I know but with some cisterns you get two bottom entry holes, torbeck on one for mains and vertival float on other for gravity feed, both aa breaks on them and higher than central siphon with in built overflow to meet regs, impossible for rain water to get into mains via mains fed valve. works for my wcs with rainwater tank feed off flat roof