# Forum Home Renovation Water Saving Garden Ideas  Cost: Pumping tank water vs using town water

## opinio

I live in an east coast capital city in Aus with a 2000L tank with a 550W Onga pump. I can have the tank water hooked up to the toilets and washing machine or use the town water (I have a manual town/tank switch - easy to do). I am wondering if the cost of pumping at 550W 'free' tank water is more costly than simply using town water. Obviously I pay for the town water but it is pressurised. While I get the tank water for free but I have to pay electricity costs to pump/pressurise it. Without going into the cost per litre of town water and specific cost of electricity does anyone know 'in general' (based on standard/common residential utility costs) whether it is cheaper to use tank water or town water in my setup? I have modern 3L/4.5L toilets and the pump runs for about 25 seconds to pump and re-pressurise when I use a 'number two' 4.5L flush. I have a highly water efficient front loader washing machine. I don't know the litres per wash but it was one of the most efficient I could find (stars wise) when I bought it  year ago. 
Any comments greatly appreciated.

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## Sir Stinkalot

Where we are water use is relatively cheap. We get stung by the service charge  (which is based off a property valuation for some unknown reason) and sewer charges. There seems to be little incentive to actually use less water. 
You should be able to calculate the comparable running costs if you can find the costs of water and electricity off your past bills and then run the numbers. A 2000l tank isn't particularly large however so you may be changing over quite often.

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## chrisp

> Without going into the cost per litre of town water and specific cost of electricity does anyone know 'in general' (based on standard/common residential utility costs) whether it is cheaper to use tank water or town water in my setup?

  I'm confused!  I think that you do need to go in to specific costs to work out 'in general' which is cheaper.

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## SilentButDeadly

Cost of pumped rain water and town water per kilo litre is near enough the same to be negligible. And you'll pay the service charge for town water regardless... 
Actually I think the ATA did a price comparison a few years back...check their website.

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## opinio

> I'm confused!  I think that you do need to go in to specific costs to work out 'in general' which is cheaper.

  I would have thought give or take a few cents of 5% or so the costs of utility services is generally the same for east coast capital cities. I could work out a per litre cost for water I guess but I don't understand electricity at all except that the pump is 550W. 
I was hoping that some one could say something like 'in general the coast of pumping is about a quarter of the cost of water supply from the two' or something like that. Perhaps I am wrong I guess. 
My tank is only 2000L but it is running over at the moment and I have no need to water the garden so I was just wondering if it is even worth using tank water or should I juts leave it (for the garden) and continue with town water. 
Still, if anyone has an idea happy to hear from you.

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## opinio

> Cost of pumped rain water and town water per kilo litre is near enough the same to be negligible. And you'll pay the service charge for town water regardless... 
> Actually I think the ATA did a price comparison a few years back...check their website.

  Thanks Silent. So I guess I am not out of pocket as such, but not a saving as well.

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## chrisp

The electricity costs will probably quite low too - much like the water costs as pointed out by Silent. 
As a start, you mentioned that the pump runs for 25 seconds.  Using this and assuming that the pump runs at full load (550W), the cost for that 25 seconds is roughly: 
25 (seconds) / 3600 (seconds per hour) x 550 (W) / 1000 (W per kW) x $0.235 (electricity cost per kWh) = $0.0009 electricity per flush!

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## opinio

> $0.0009 electricity per flush!

  And that's a 'number two' flush as well.

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## chrisp

> And that's a 'number two' flush as well.

  Spend a penny!!!  :Biggrin:

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## Marc

There is no easy answer to this as there are more variables. Only the variation in both bills may give an idea of saving versus no savings. 
Continue doing what you are doing and look at the changes in the bill.
Meantime I suggest  to take up a hobby.  :Smilie:

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## cyclic

I did the calculations many years ago when Qld was running out of water and the answer is, it is not worth it because
(1) 2000 litre tank is useless and you will need a swap over arrangement (davey rainbamk or similar) to allow town water to be used when the tank runs dry, therefore
(2) You have to factor in the cost of connecting town water supply to the tank including rainbank or similar
(3) Also the cost of connecting to the toilets and wash machine
(4) Also the cost of pump repairs down the track
which leaves the cost of electricity as a minimal consideration. 
Have a look at your current water bill for the cost of 2000 litres and I believe you will understand what I am getting at.
At a guess I think water is currently costing you probably $6 for 2000 litres.
And one last consideration is the pump will most likely cycle ie start/stop while filling the toilets,which won't do it much good.

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## Marc

I have a 40,000 L Tank, 3 bathrooms, and laundry and kitchen of course. The pump goes on and off all the time, we don't even think about it. No town water ... well no town either ha ha.
The pump has been doing it's thing for us for the last 7/8 years and for the folks before us for another 10 years so that makes it 18 years old.
Nothing to it. only needs air pumped in the little pressure tank thingy from time to time.
The extra electricity used by the pump? aside from electrical hot water heater, and 4 or is it 5 split aircon and hours of welding and cutting and many other electricity run motors, power tools lights, outside spot lights, did I mention lights?  
The difference If we ever got water piped to us?
Nothing because we don't pay for the rainwater, not yet that is, eventually some frog will find a way to bill us but for now rainwater is free, town water is paid.  
If urban rainwater tanks had any chance to save you money, they would be banned, verboten, illegal.   :Rofl5:

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## Uncle Bob

> Spend a penny!!!

  I think that's what the OP is trying to avoid  :Smilie:

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