Rainwater system help required

[Matt300]

Hi all,

I am thinking of installing a rainharvesting system to feed loo's, an outside tap and maybe the washing machine.  I have a spare cold water tank in the loft (left over from when I changed my house to mains pressure system), I am hoping I can put a larger holding tank in my garage to feed the header tank in the loft via either a solar or mains powered pump.  I will need to change the pipework to the loos etc to be fed from the header tank and fit a pump up from the garage tank which will be fed from a RWP on the garage (the garage RWP takes all the water from my house and can fill a water butt in minutes).

I have a few questions which hopefully someone may be able to

1 - I assume I will need a mains water feed to the header tank just in case I run out of water, I assume this can be controlled with a stop cock.

2 - How can the pump be controlled to pump up more water from the holding tank when the water level reduces in the header tank.

3 - Is it best to have a mains or solar pump.  Does the mains pump cost so much it would not actually save any money?  I am assuming the mains pump would be more expensive to run but more reliable and will work during the night aswell if needed.

4 - Any idea how big the tank in the garage should be, I would prefer something tall and narrow if possible?

I live in a 3 bed semi with 2 WC's and currently 3 people living in the house.

Any answers/advice much appreciated.  I am hopefully going to do this myself with the help of a plumber, do I need to inform anyone or is anyones permission needed?

Thanks

Matt

[dhaslam]

Something like this would control the  pump.   
www.deanbennett.com/mechanical-float-switch-for-fill.htm

Very little advantage of solar pump,  you would need water by night as well as by day .     There is a seasonal aspect to rainwater   so you need to look at the monthly rainfalls for your area and compare that to your usage.   Probably something like three weeks storage is enough. At say 50 litres per day the tank would be about 1000 litres.   A 1000 litre tank is quite small, just one metre cube.      I lived in a house which used rainwater only and  the main tank was  about 3000 litres  but it supplied everything.  It was fed from about 50 sq metres of roof with one metre rainfall per annum.   

[renewablejohn]

You could use a 12v surflow pump similar to that used on a boat with a normal ballcock. The pump has an automatic pressure cut off switch when the ball cock closes. 12v battery and solar battery charger to be totally independent. Old fruit juice tanks are good for water storage being black plastic you do not get the algae problem associated with normal IBC containers.

[northern installer]

hello Matt.You need to be careful about cross contamination,I have brought a 'grey' water supply to each toilet cistern,terminated in a ball service valve;the clean water supply is similarly terminated adjacent to this.A flexible tap connecter joins the service of choice to the cistern;therefore no chance of cross contamination.

[rhys]

Important too that at the header tank there is the required air break between the mains feed and Rainwater in the tank. Suggest you review the schmatics on  the various rainwater harvesting suppliers websites.
Another option, although possibly more expensive, is a pump station which "sucks" the water from the large storage tank direct to the "greenwater" supply pipes on demand. These systems do not require a header tank and include various controls to draw mains water when rainwater is unavailable.
The tank exchange sell the recycled bulk orange containers.
http://www.thetankexchange.com/home.htm

[guydewdney]

similar IBC (as the 1000 litre ones are called) are available from a lot of industrial chemical companies, oil recyclers, etc) - I pay 20 quid a tank...

[Much]

3 - Is it best to have a mains or solar pump.  Does the mains pump cost so much it would not actually save any money?  I am assuming the mains pump would be more expensive to run but more reliable and will work during the night aswell if needed.

Exactly why I'm currently looking for an easily available mechanical diaphragm pump - I'm going to stick a VAWT on a pole, and have it slowly pump (mechanically, no electrical conversion) from my underground tank into a series of header tanks in the garage loft space, and from there into the house. 
Of course, even if a VAWT is supposedly able to cope with turbulence well, I'm not going to mount it on the house what with all the vibration horror stories for the traditional 'propeller' generators. 

Failing to find a low power dia pump, I'll just make my own. I'd just prefer to source a 'standard' bit of kit.

[billi]

hello

why not pumping it direct from the underground tank into the toilet and washing maschine
without header tank ?


Billi

[David]

A header tank often allows any small problems to be rectified before they become big problems.  It can also be filled from the mains if necessary.

[David]

I am thinking of installing a rainharvesting system to feed loo's, an outside tap and maybe the washing machine.

Not an answer to any of your questions, but a suggestion of where you might get some ideas.

I went round Earthship Fife yesterday <http://www.sci-scotland.org.uk/index.shtml>. This is a visitor/exhibition centre which is not connected to any external services. Electricity comes from hydro (10m head onto a small turbine), wind and PV panels, which all charge up batteries. From this they run computers, lights and the most important item, the kettle.

Water comes from the roof. This goes into a 1000 litre drum via coarse gravel filters. From there it is pumped by a pressure activated pump through a couple of filters. Drinking water also goes through a UV filter. Hot water is produced in an "unvented" cylinder using immersion heaters which are part of the system to absorb excess electricity.

Having run out of the sink the water runs through the plants in the solar buffer area (you can just about see these plants in the photograph on the home page).

The water is then pumped back to the toilet (a fairly standard toilet, though with a three setting variable flush system).

From there the water is taken to a greenhouse, which has to be 10m away from the dwelling in Scotland. There the solids are broken down and the plants irrigated. Any excess water in the greenhouse is transferred to a bed outside the greenhouse.

Earthships were started in the USA, often in desert or semi-desert areas. This one was built along the same lines as an experiment to see what works and what doesn't work so well in a different climate. The lessons learnt are the fairly obvious ones that water is not so important in Scotland, but heat is more important. Some of the ideas can be adapted to other sorts of building.

They have an on-line shop and the Earthship Toolkit has comprehensive information on the systems.

[Much]

hello

why not pumping it direct from the underground tank into the toilet and washing maschine
without header tank ?


Billi

In my case; it allows for a constant slow low-power flow to the header, from which a fast flow can be provided on demand. Rather than a high-power / pressure requirement for a shorter period of time. Essentially, the header being a mechanical battery.
Of course; the 'professional' control-panel solutions almost always feature a high-pressure on-demand pump. But this requires both the electronics, plus the mains electricity (plus high pressure components)

[northern installer]

- I'm going to stick a VAWT on a pole, and have it slowly pump (mechanically, no electrical conversion) from my underground tank into a series of header tanks in the garage loft space, and from there into the house. 
Of course, even if a VAWT is supposedly able to cope with turbulence well, I'm not going to mount it on the house what with all the vibration horror stories for the traditional 'propeller' generators. 

Failing to find a low power dia pump, I'll just make my own. I'd just prefer to source a 'standard' bit of kit.
[/quote]



Much,try this for low cost pumping bodge;use an  'AC' mechanical lift pump from a car,driven by a cam from your vawt;they will pump to a modest pressure,then idle against the internal spring until the diaphram returns for more pumping;small flow,but over a period of time might be enough?

[Matt300]

Hi,

Thanks for all the advice and comments, I am putting the tank in the garage (I have a very small garden) and therefore the header tank in the loft will add capacity and also allow me to add mains water if I run out.  It is alot easier for me to feed the WC's from this header tank, some of the pipework is already there.

Any suggestions for pumps etc grateful, I think a mains pump sounds best but not sure of the running costs.  I would love a rectangular tank that is up to 8 feet high but not too wide or deep that could fit in the back of my garage.  Any ideas welcome.

Matt

[dhaslam]

If you raised the tank a little you could fit the front of the car underneath, if that is the limitatiion.        There are some 12v bilge pumps for boats which are very reasonanble and may switch off when connected to a normal ballcock.    This is an example


http://cgi.ebay.ie/BRAND-NEW-12V-3000GPH-TMC-BILGE-PUMP-chandlery-marine_W0QQitemZ160229798274QQihZ006QQcategoryZ15263QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

It uses 200 watts but does 3000 gallons per hour so it  would only have to run for a few hours in the year, less than one kilowatt.   

[Paulh_Boats]

A note of caution on bilge pumps, I've read many reviews in the boating press.

The flow rate is significantly reduced with a full head or with narrow pipes less than 25mm. Consult the manufacturers graphs. Also some pumps deliver less than the claimed flow rate during tests.