Look at your bill and see how much of it is for sewage, costs me more than the water I buy in. That bit shoudl not change as you will still be using the same amount, just from a different source.

Peter in Hungary, you are right on the principle. Sewerage is measured at (as far as I remember) 90% of metered water 'in'. So using harvested RW will reduce sewerage charges.

In answer to the OP, how much you save depends on the accuracy of your estimates, and your knowledge of cistern capacities, whether or not you have variable flush devices etc. Also on lifestyle. To put it indelicately, where are you when you want to pee, dump etc? If you are out a lot then your flush consumption starting-point is going to be lower.

Mightyworthit:

Attached are sample calculations to BS8515:2009 which indicates that for 5 people and dual flush WCs a 2,700 litre RWH storage tank is recommended.

The yield from the roof depends on rainfall and collectable roof area (mid terraces can only collect from one side of the roof for instance). Your tank would be suitable for a 55m2 roof collector area.

The calculations indicate that a larger tank would be better but if you have a free tank, use it!

The normal use for WC flushing is 5 x say 30 litres/day = 150 litres. A full tank would give you nearly a fortnight's use until the next rainfall. Should just about work

The maximum amount of rainwater recovered per year is:

Potential Recovery = (Annual Rainfall in m) x (Roof Coeff) x (Filter eff) x (Roof Area)

for the example of 55m2 roof and 1,000mm annual rainfall:

Potential Recovery = 1 x 0.8 x 0.9 x 55 = 39,600 litres, or 39.6 m3.

Multiply the m3 by the amount you will pay for water and sewerage / m3 from your friendly local water supplier to get the potential maximum saving per annum. In practice you will get less than this as there will be some tank overflow in heavy rain and when away on holidays.

If you have a larger roof your recovery will not increase pro-rata - there will be more rainfall wasted to overflow.

I don't understand your comment about strengthening the roof - surely the tank will be at ground level or underground and water pumped via a sump pump with float switch up to a smaller header tank in the roofspace with dual ball valves - one for recovered water and one for mains water (ballcock on the mains adjusted to only operate at a low water level).

Regards, Gary

An interesting point, and if you are on mains water and sewage probably not financially worth it. If they every use our 'waste' to make energy on a large scale, they could/should possibly surcharge people who do not use the main sewage system.
But having said that, go to the beach at Portreath after a heavy rainfall and work out why there is a brown stain running across the beach and where all the cotton buds come from. Domestic rainwater harvesting could help alleviate that problem.

This may help - about 26% saving on flushing toilets and 12% on washing and 7% on outdoor/car washing.

Oh yes, and never go swimming near an outfall after heavy rain - even on designated beaches - overwhelms the sewage treatment system.

http://publications.environment-agency.gov.uk/PDF/GEHO1110BTEN-E-E.pdf

When I lived in Swansea in the '70's (before the days of colourful wet-suits) the local joke was that the water-skiers went out in black wet-suits and came back in brown ones...

Thanks for all of your replies
I found this water meter comparison calculator.
By fiddling around with the numbers you are able to come up with some guess-timated figures

http://www.ccwater.org.uk/server.php?show=nav.388

My decision is based now on how much I stand to save by going on a meter..if any!
Then by installing RW harvetsing how much this will further save me.

Then I have to ask myself does this total saving justify the £2000 odd pounds its going to cost me to install (plus my time to do the work)

BTW does anyone have any idea what sort of pump I would be best using? I am intending to pump from a well/ underground holding tank (capacity 2000l) To a cold water tank in the loft 6m up.

tim

If you are pumping to a tank 6m above the ground from an underground tank, say 1.5 m deep, then the pump will have to supply water at sufficient pressure to deliver the required flowrate through the ball valve in the loft tank.

To achieve this, the pressure remaining at the ball valve inlet should ideally be 0.5 bar, or 5m head, giving a total pump head of 6 + 1.5 + 5 = 11.5m. The pump has to deliver this head at the required flowrate depending on your demand / pumping duration.

The submersible pump + float switch combo suggested by Tony is definitely the way to go - these pumps are reliable and well proven technology. Good brands are Grundfos, Lowara, Dab or Wilo.

Posted By: renewablejohnWhat are water rates??

What we pay not to pollute the surrounding area.
Seems valuing nature is all the rage at the moment.

£2000 plus time/labour and then upkeep, changing pump/filters every so often, plus the fact that it only provides a proportion of your water needs doesnt seem to make economic sense to me. Even environmentally all that embodied energy in pumps and plastic must throw some doubts on their green credentials too? I do want to be sold on the technology though......makes so much sense. I use roof water in a 500litre gravity feed tank for the garden and it works a dream.

I quite fancy the idea of using a hand-operated bilge pump to lift the water from the reservoir to a holding tank. Low maintenance, no electricity and good exercise.

They charge based on the meter readings for clean water supply.

About a year back I was assisting a Client who had a site water leak and who was being charged not just for the leaked water but also for the mains sewerage on a pro-rata basis - I was able to get the water authority to drop the sewerage charges as it was quite clear that the leaked water did not enter the mains sewer system.

Mike up north

Pumpimg to an intermediate tank allows me to have a mains feed to this tank as a back up, on a seperate float valve. I would not be able to install this sort of back up in the reservoir, impractability being the main factor.

I cannot be certain that the reservoir is one of unlimited supply.

In fact I know that it isnt.

Tim

Seascape, what is to stop you paying them an amount based on 5/6 of your August bill, then asking them to re-calc your DD?

I did get it sorted eventually and pointed out that I had paid for my water usage from Feb 12 by monthly direct debit, it was just 'unbilled', which is not the same thing as unpaid.

I have asked for a formal explanation as to why this usage is considered unpaid and used in the calculation for future payments. So far no explanation given, just an apology and agreement I should pay just 8% increase.