Pumping

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.
Reply to
Kim Siddorn
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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.
Reply to
Dave Liquorice
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
Reply to
Kim Siddorn
About that, it varies a couple of feet with the atmospheric pressure. B-)
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.
Reply to
Dave Liquorice

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