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Efficient pumping for gravitational water cooling

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New Member
Mar 6, 2001
I would like to build a water cooling system, where water flows down due to its own weight. A reservoir is in the cupboard above the computer, and another reservoir is below the computer. Water is pumped back up from lower to higher reservoir.

The flow rate is high, about 4 liters per min, when the water reservoir is 60 cm higher than the output pipe. A 8 liter bucket would empty in two minutes. The pumping must be really effective.

The good thing about the reservoirs is that a single pump isn't needed. If an efficient pump is expensive, two small pumps can be used. But which is cheaper? Getting one big or many small?

Then there is also the problem with the flow rates. If the pumping is slower than the cooling flow, the upper reservoir will empty, cooling will be ineffective and bang!
The opposite isn't that bad, but the constant "slurping"...
well 1 pump is easyier to setup...but 2 could give you some extra security, if 1 fails you still have the other but it would have to be strong enough to pump all the water...personally i would stick with 1 myself and try to keep the water reserve as level with the compuer as possiable...
why do you want 2 reservoirs? in the end the easiest solution is 1 reservoir at same level with computer and a good pump. Make sure you put it at same level with the computer, because when pumps pums against a gradient -such as through the tubes, or up to a reservoir- their flow rates go down fairly quickly.
Think the upper reservoir like it was a tower, which is used to generate the pressure of tap water.

The idea is to store the pumping energy into potential energy, which releases more uniformly than pumping. The water can flow really quickly, but the pump can run slowly, as long as the flow rate is the same. The pump can suck, so it doesn't have to generate pressure, which will make the pipes swell a little.

There is also some other safety things. You are correct that the machine can be still used if one pump fails, but only with its power. If both pumps fail, you can pour the water in for yourself. A normal pump failure would mean that you can't use it. This way it's hard, but possible. Then if the pipes leak, all that has to be done is to cut the water input from the upper reservoir. Most of the water left will pour to the lower one, not leak thru pipes.
The problem you'll have is that pumps are more stressed, and don't pump as well if they pump to a height higher than the height they sit at in an open loop. If you were to circulate it back down to the pump through the same tube, you'd have a siphon effect on one half, thus making the "head" 0. I really can't see any reason for wanting the water to be gravity fed, it would go much faster with a pump.
Feeling kind of dumb here.... correct me if I'm wrong you still need a pump of sorts to return the water.... why not just have it pump the water for you.