In the limit, open channel flow uphill is limited by the velocity head of the mass flow at any point and usually less. Over/across/thorough mountain ranges usually takes closed conduit(pipe) and pumping or higher elevations at the start. Vacuum siphons are limited to about 30+ft. or so, depending.
Collectors way above the pool surface, say 35- 40 ft. or more under no flow conditions will be a vacuum siphon and probably less than ideal design. Depending on the design, under zero flow conditions, the water in the collectors could "boil" at reduced pressure - partial vacuum and push the water in both directions depending on/if any check valves or other devices in the system. Over about 30 ft. or so, you'll have a vacuum siphon regardless and a check with the pump curve will be a good idea. A flexible collector could suck up and collapse under the vacuum. The pump may not be able to handle the head on startup. Depending on H2O chemistry, "boiling" may precipitate scale on the collector interior wall. It just doesn't sound like a good idea for a lot of reasons. I'd keep the height diff. below 25 ft. max. or less depending on height above sea level.
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Low mountain ranges, or high pressure at the source though.
You can reduce the energy loss of pumping the water, but any place along the way where the water pressure goes negative (not just below atmospheric pressure) will tend to break the siphon.
If you keep the pressure in the line high enough that the entire length of the pipeline is at a positive pressure, then all you have to do is recover the "leftover" energy with which the water arrives at the far side of the mountain range and use it to balance the work you did raising the pressure at the supply end.Leave a comment:
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hence the "keep it filled with water". There are aqueducts that use siphon to get water over mountain ranges.Leave a comment:
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Depending on elevation change and design (vac. breakers/lack of ?), could a partial vac. at the top of the system cause a local system pressure below sat. press. of the H2O at some ambient temp. to exist under no flow conditions ? Depending on alt. above mean sea level, 30+ ft. or so above the pool surface will get close to a full vac. on a tight system.Leave a comment:
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once you get the air out of the pipes and collectors, and keep it filled with water, you essentially have a siphon, and only need a small pump to maintain flow.Leave a comment:
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Hillside installation - where is best?
We are located on a hillside. The pool is below the house, the pool equipment is below the pool level (approx even with the bottom of the pool). We have a two story house with the crawl space about one story above the waterline.
There are two potential locations:
- The hill slope above the pool.
- The roof of the house.
The roof of the house gets the best sun exposure. But it would be about four storeys above the pool equipment. The head would be less for the hillside. But the hillside has slightly less sun and needs preparation (frame) for mounting.
Is this height difference a big issue. What is recommended in this situation? Do I need a high powered pump?
We live in California, so freezing is not an issue.
Thanks for any advice.
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