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gravity siphon calculations advice

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Hi all

I have recently taken the plunge a bought myself 5 acres and relocated a beatuiful old wooden cottage onto our Land in Northern NZ. Summer is approaching fast and my roof rainwater catchment
isn't enough too water my fast growing vegetable garden and new Orchard. When i prepared the house site i also dug two large Dams on the property to see us through the droughts we have here sometimes in the summer.

Does someone know how to work out the gravity pressure and pipe size for a gravity fed water source for my house. I have been out today with a large pole and some rope to measure the fall from my top pond.
Head for top pond = 3.8m the distance to my garden is 75m.
Will i get any pressure from this? What size pipe will i need to overcome the drag for this distance?
I think i will probably need a tank near my garden/house where i can collect the water and perhaps a small pump so i can run some irrigation??

My second option is a larger Dam about 30m circumference and 4m deep. This one is about level with the house and around 60m from my garden.

Would appreciate any advice for my system and love to hear about your systems too.

Any advice or assistance hugely appreciated


Any help or advice much appreciated

permaculture expert
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15 meters head is roughly equal to town water pressure and the larger the pipe the less frictional loss of pressure and more volume capacity so the most efficient and cost effective would be 50mm (2 inch) otherwise the fittings would be cost prohibitive. You would be best using your high dam as your header tank and fill it when needed from your lower dam and reverse sysphon back down the same line, making it very easy to reset your syphon anytime you need to. Ar 3.8m head you will probaly be able to run low pressure sprinklers on short stand pipes.
B Freeman
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Cheers Geoff

Thats great advice. What do you mean by reverse Syphon down the same line???
I hoped i would be able to top up the header dam from the bottom. I estimate the fall between the two dams at 4-6 m and distance around 80-90m. The bottom dam is around 60m from my house/power.
Would this be a large expensive pump?? Electrical or petrol?? What size line should i run back up to the top dam?? Can it be smaller?

Thanks very much your advice aprreciated
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