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Topic # 150034 9-Jul-2014 11:39
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With the outage going on at the moment I'm concious of what is sucking the life out of the solar battery bank .. and a big hitter is the waterpump (on tank water here).

Anyone have some suggestions of where I can look to find a low power use waterpump for the house ?

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  Reply # 1085629 9-Jul-2014 11:49
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With electric motors, while some are more efficient than others, the differences are not big.  You would just have to move to a lower wattage and therefore lower pressure pump.  That might make showering impractical for example.

If you needed a certain volume of water (e.g. fill the bath) you would not be saving money as a half-power pump would need to be running twice as long to fill the bath.  Again there might be some efficiency differences but these would be small IIRC.

A baby generator to top up the batteries might be worth looking into.

I bought one of these http://www.thewarehouse.co.nz/red/catalog/product/Inverter-Generator-800W?SKU=1697039 about 12 months ago for $400 (now I see they are on clearance special!!) and find it quiet and easy to start.  Mine came with a cable for charging a 12v battery - T connector generator end and croc clips on the other.




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  Reply # 1085641 9-Jul-2014 12:01
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Electric pumps are generally pretty much of a muchness,

you could look at a potentially larger header tank? and limit the pump to run mostly in daylight hours when you have some solar input?

Are you pumping from a bore/well or a flowing source?

If you have a flowing source, you could look at running a Rampump

http://en.wikipedia.org/wiki/Hydraulic_ram 

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  Reply # 1085681 9-Jul-2014 12:44
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Can you turn the pump off for a bit when you don't need water to eek out your batteries a bit longer?



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  Reply # 1085697 9-Jul-2014 13:09
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Maybe I should be looking at a header tank in the roof space instead then ?

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  Reply # 1085701 9-Jul-2014 13:25
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Mark: Maybe I should be looking at a header tank in the roof space instead then ?

Weeeellll......  cost vs benefit...  I would see that being hard to justify unless you are happy to do the work yourself (and take the insurance risk if it leaks).

I still suggest the little generator option, but that might be because I'm a bit of a petrol-head.




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  Reply # 1085702 9-Jul-2014 13:26
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There seems to be quite a bit of difference between different pumps with similar flow rates according to this http://www.choice.com.au/reviews-and-tests/household/energy-and-water/saving-water/rainwater-tank-pumps-review-and-compare/page/results.aspx

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  Reply # 1085706 9-Jul-2014 13:31
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Unless you have a decent ceiling height, you'd want the header tank higher than in-roof to get any decent pressure at showers etc.

 

We don't have a header tank at our current house (so have no water in power cuts - going on 16 hours now), but in our last one we did, and it was above the roof (so about a 2.5m fall from bottom of tank to floor) and it was only just enough to shower with (yes we had low pressure fittings and hot water cylinder) and filling the washing machine/dishwasher took quite a while. Damn good in a power cut though, as the header tank was large enough for about a weeks water when full.



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  Reply # 1085732 9-Jul-2014 14:14
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A bit of thinking needed I think :-)  I could easily get a water tank on stilts outside the property, but would need to check local rules about it :-)

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  Reply # 1085755 9-Jul-2014 14:42
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We run a small commercial business (backpacker's hostel) from tank water, in an area that has very intermittent power - in fact the power's likely off there now...
A header tanks a great idea. For short power cuts it carries us through with just the batteries and inverter.
It allows us to set our pumps so they don't cycle on & off, which saves power and pump wear.
The key, as mentioned above is having enough head to supply sufficient pressure.
Just be aware you'll need a very sturdy tank stand if that's the way you go.. water's heavy:)

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  Reply # 1085762 9-Jul-2014 14:48
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Sidestep: Just be aware you'll need a very sturdy tank stand if that's the way you go.. water's heavy:)


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If you are thinking of sticking a decent sized headertank any height in the air. get an engineer to design the structure and use somethingstronger than 4*4s ,
Remember for every 1000 litres of water you have in your tank, its a static load of 1 tonne,



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  Reply # 1085781 9-Jul-2014 15:06
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wellygary:
Sidestep: Just be aware you'll need a very sturdy tank stand if that's the way you go.. water's heavy:)


+500

If you are thinking of sticking a decent sized headertank any height in the air. get an engineer to design the structure and use somethingstronger than 4*4s ,
Remember for every 1000 litres of water you have in your tank, its a static load of 1 tonne,


hehe ... only got suggested the idea today so no plans for anything of any size yet :-)

gzt

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  Reply # 1085850 9-Jul-2014 16:43
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Mark: Maybe I should be looking at a header tank in the roof space instead then ?


Typically header tanks are installed on top of the roof. For height, and its just safer if they overflow with a pump control failure or random leak it just goes down the spouting like rain. Energy wise a 12v pump just for that scenario might be the most efficient.

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  Reply # 1085891 9-Jul-2014 17:30
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Just a few thoughts...

Head height for a standard low pressure system is 6m, which is essentially the same as on top of your roof.  Or if you have a sloping site, put it higher up on the slope.  Pressure is not great, but you can wire in a small pressure pump which could be wired to run only if mains available.

Or get a pump that can run at a lower speed when on batteries, so you have less pressure but longer battery run time.  It does not help much when e.g. running a bath where you need a certain volume rather than pressure, but running slower will reduce the current draw which reduces cable losses and battery losses.

If this is one of those large mains powered pressure pump, see if you can either get a lower voltage DC pump to run streight off batteries without inverter losses, (but make sure you have decent cable thickness).  Or consider a few small pressure pumps distributed through the house plumbing so that the pressure is applied only where taps are opened rather than across the whole plumbing system.

Increase pipe diameter, which reduces water flow resistance and thus pump load and power consumption.




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  Reply # 1085893 9-Jul-2014 17:44
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Dynamic: With electric motors, while some are more efficient than others, the differences are not big.  You would just have to move to a lower wattage and therefore lower pressure pump.  That might make showering impractical for example.

If you needed a certain volume of water (e.g. fill the bath) you would not be saving money as a half-power pump would need to be running twice as long to fill the bath.  Again there might be some efficiency differences but these would be small IIRC.

A baby generator to top up the batteries might be worth looking into.

I bought one of these http://www.thewarehouse.co.nz/red/catalog/product/Inverter-Generator-800W?SKU=1697039 about 12 months ago for $400 (now I see they are on clearance special!!) and find it quiet and easy to start.  Mine came with a cable for charging a 12v battery - T connector generator end and croc clips on the other.


IMO this would be the simplest and maybe the cheapest idea, and has the added benefit of being able to run other appliances. obviously you would need to have some petrol.

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  Reply # 1086164 10-Jul-2014 03:55
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Our hostel's on the high point of our property.
When we designed & built it we were not yet grid connected and looked at many options.
We're in a 'very high' wind risk area of NZ, and the design required for the water tower meant it'd be a bit of an eyesore.
The building's 2 storey, with a 45° roof, we were able to build a large header tank into the roof space with a few design changes to trusses and joists to support the weight and allow for the overflow tray.
The overflow exits just under the eves of the roof to avoid extra piercing of the long run steel.
We've also installed a 'high water' alarm in the tray that just sqeals right now, but will be integrated in the pump control in the future to shut it off in case of overflow that exceeds the draining ability of the tray.
With larger diameter supply lines, 6m+ head, low pressure showers etc we have excellent supply in the lower level of the building.
Upstairs, with 3m head we only have 2 shower/toilets requiring supply, and they're usable.
However, paying guests require good showers, so we've installed small inline booster pumps. They don't work when the power's off, but the big complaint is "our shower doesn't have much pressure" rather than " we have no shower or toilet"
We've been mains connected for many years now, but have regular outages - 15 last year.
Many of those were for just an hour or two. We have a small battery bank/inverter unit - which doesn't automatically supply power to the pressure pump, and a 25kva diesel generator. The beauty of the header tank is it doesn't require us to start the gen for those short power cuts, and doesn't require us to sort things out at 2am on a stormy night when the longer ones usually start.
It also doesn't require our pressure pump to cycle on/off like crazy as multiple people in the building have showers, flush toilets, and turn taps on and off.
I saw a clever alternative installation, in a 30° residential roof where the guy had hung a length of capped PVC pipe all the way along the ridge of his house, supported by the collar ties to use as a header tank.
3rd world but effective.

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