We have just excavated a fire pond at our permanent site. We need 60,000 
litres to satisfy fire regs but never ones to do things by halves, I thought 
it would make sense to have it both deeper and wider than we needed and it 
ended up being some 30' deep and 70' across! The last cut entered a sand 
lens & water started to run into the hole. It wasn't lots, but when the HUGE 
liner was in, I thought it would be good to remove the water via the 
anti-hippo pipe & transfer it into the liner. Starting at 5.00pm, I thought 
it might take an hour or so & our little 25 years old Briggs & Stratton pump 
laboured away to lift the water that high. After a lot of priming, we 
eventually got it to run OK & it pumped manfully for about an hour until it 
petered out and died. Seized solid more like ......... ;o((

Across the road to the hire yard (only been there a week!) and hired another 
somewhat younger electric pump, running this off our fifteen year old Robin 
powered 2 KVA genny. After a few false starts, this ran just fine, 
delivering about a litre a second or thereabouts. The Robin Bas**rd is 
small, nicely formed but thirsty, emptying its tank in two hours as against 
our Honda genny of 2.2kva which would run from 10 - 4 on about the same 
amount of petrol.

I thought it might take an hour or so to transfer the water from under the 
liner to inside it & was surprised when it ran on and on, the 25mm cold 
water pipe enclosed water column finally collapsing at 11.45! Obviously, we 
have struck water & I am interested to see how the supply holds up in the 
months to come - we are only there 26 days of the year in two day 
increments, so a daily supply is not necessary.

A couple of questions: What sort of pump do we need that will not need 
priming every time we want to use it? I thought that a Petter A would be a 
good engine to use, air cooled, frugal and easy to start, but not sought 
after enough to get itself stolen! The site is reasonably remote.

regards,

Kim Siddorn

Teach a child to be polite and courteous and you create an adult that can't 
merge a car into faster traffic.

On Thu, 28 Aug 2008 02:10:47 +0100, Kim Siddorn wrote:

> A couple of questions: What sort of pump do we need that will not need 
> priming every time we want to use it? 

One you can put at the bottom of the hole to push the water up rather than 
have at the top of the hole and try and "lift" the water. Your hole at 30' 
deep is only a couple of feet short of the maximum water "lift" you can 
do. When lifting water in this way you are actually trying to create a 
vacuum and atomspheric pressure on the free body of water pushes it up 
into that vacuum, until the weight of the water colum equals atmospheric 
pressure were upon you don't get any more lift. Think mercury barometer.

Maybe have a couple or three sump pumps each lifting in say 10' stages 
into a holding tank with a pump in to the next stage. Each pump won't be 
working as hard to push up it's ten foot rather than a single pump doing 
the whole 30'. If all the pumps are the same make/model they should keep 
up with each other, get ones with auto on/off so if one pumps faster than 
the one below it it switches off until the water level in it's holding 
tank has risen.

-- 
Cheers
Dave.

I was vaguely aware that atmospheric pressure played an important role in 
the height that it was possible to lift water, although couldn't remember it 
exactly - 32' I believe? I'm not sure if it applies in this case as the 
liner is heavy & may well have sealed off the top of the exposed water 
beneath it before pumping commenced. Certainly, once we got it going the 
electric pump was delivering perhaps a litre a second initially, although 
this rate dropped after a couple of hours. You could hear the cavitation 
around the impeller, but it continued to pump increasingly smaller amounts 
until the column collapsed. My guesstimate is that we shifted around 2,500 
gallons.

Here's the question. Once it was sealed from the outside air and a 
continuous enclosed column established, was atmospheric pressure relevant? I 
don't think the ground water was at any great pressure as it just flowed 
slowly into the hole from the sand layer.

For good or ill, we are now stuck with what we have: a big blue linered 
hole that we expected to largely collect rain water and, trapped between 
liner and the clay, two 25mm cold water pipes in a fetching blue colour. It 
would obviously be useful to have access to ancestral water for potable 
supplies and perhaps top up the pond & moat in the dry weather. The panel's 
opinion on suitable pumps at ground level, hopefully capable of being driven 
by a Petter A1 are eagerly sought.

regards,

Kim Siddorn

"Dave Liquorice"  wrote in message 
news:nyyfbegfubjuvyypbz.k6bgmk2.pminews@srv1.howhill.net...
> On Thu, 28 Aug 2008 02:10:47 +0100, Kim Siddorn wrote:
>
>> A couple of questions: What sort of pump do we need that will not need
>> priming every time we want to use it?
>
> One you can put at the bottom of the hole to push the water up rather than
> have at the top of the hole and try and "lift" the water. Your hole at 30'
> deep is only a couple of feet short of the maximum water "lift" you can
> do. When lifting water in this way you are actually trying to create a
> vacuum and atomspheric pressure on the free body of water pushes it up
> into that vacuum, until the weight of the water colum equals atmospheric
> pressure were upon you don't get any more lift. Think mercury barometer.
>
> Maybe have a couple or three sump pumps each lifting in say 10' stages
> into a holding tank with a pump in to the next stage. Each pump won't be
> working as hard to push up it's ten foot rather than a single pump doing
> the whole 30'. If all the pumps are the same make/model they should keep
> up with each other, get ones with auto on/off so if one pumps faster than
> the one below it it switches off until the water level in it's holding
> tank has risen.
>
> -- 
> Cheers
> Dave.
>
>
>

On Thu, 28 Aug 2008 18:56:59 +0100, Kim Siddorn wrote:

> I was vaguely aware that atmospheric pressure played an important role 
> in the height that it was possible to lift water, although couldn't 
> remember it exactly - 32' I believe? 

About that, it varies a couple of feet with the atmospheric pressure.  B-)

> I'm not sure if it applies in this case as the liner is heavy & may well 
> have sealed off the top of the exposed water beneath it before pumping 
> commenced. 

Not sure the seal is relevant, you'll still have the atmosphere pushing on 
the flexable liner and have it's weight as well. Also something must have 
taken the place of the water you removed, be that air or the liner 
lowering.

-- 
Cheers
Dave.