1542 also clearly shows that IF a pump is used, it's used to push, not pull.
1270 specifically shows why a pump would push not pull. A pump wouldn't be able to pull the water up that far either, it would need to push.
1125 does specifically talk about an automobile water pump, which is a centrifigul pump, much closer in build than your example of a "piston pump." A centrifigul pump creates high pressure on the output and low pressure on the input side. Our aquarium pumps, which are typically impeller, create a high pressure on the output and a low pressure on the input side. The input side is then flooded by water replacing the removed water, in nature's way of equalizing the pressure.
I'm not comparing apples to oranges. I'm trying to show hydraulic dynamics, which a hydraulic engineer should understand already. Hydraulic dynamics will be very important to understand, in the designing of your closed loop system.
My whole point is that an over the back closed loop system can be designed correctly, with the pump below the water line. OR, it can be designed incorrectly, with the pump above the water line. If the pump is above the water line, it'll have to be designed with a way to prime it, in the event of a power outage. This is because it cannot prime itself, once it loses prime. The reason it can't prime itself is because it cannot SUCK water, well enough to replace the water it's pushing out. Melev has a couple great Over the back closed loop designs, that would work well for your tank. However, the pump would still need to be installed below the water line, and the pump would push, not pull water. As it pushes, the back end would naturally be flooded. You'd need to plumb it in a way to make sure you can keep the back end flooded. This need to keep the back end flooded is the whole reason why it's important to design a system based on the pump pushing, not pulling. If not designed, based on this premise, it just won't work properly.
1270 specifically shows why a pump would push not pull. A pump wouldn't be able to pull the water up that far either, it would need to push.
1125 does specifically talk about an automobile water pump, which is a centrifigul pump, much closer in build than your example of a "piston pump." A centrifigul pump creates high pressure on the output and low pressure on the input side. Our aquarium pumps, which are typically impeller, create a high pressure on the output and a low pressure on the input side. The input side is then flooded by water replacing the removed water, in nature's way of equalizing the pressure.
I'm not comparing apples to oranges. I'm trying to show hydraulic dynamics, which a hydraulic engineer should understand already. Hydraulic dynamics will be very important to understand, in the designing of your closed loop system.
My whole point is that an over the back closed loop system can be designed correctly, with the pump below the water line. OR, it can be designed incorrectly, with the pump above the water line. If the pump is above the water line, it'll have to be designed with a way to prime it, in the event of a power outage. This is because it cannot prime itself, once it loses prime. The reason it can't prime itself is because it cannot SUCK water, well enough to replace the water it's pushing out. Melev has a couple great Over the back closed loop designs, that would work well for your tank. However, the pump would still need to be installed below the water line, and the pump would push, not pull water. As it pushes, the back end would naturally be flooded. You'd need to plumb it in a way to make sure you can keep the back end flooded. This need to keep the back end flooded is the whole reason why it's important to design a system based on the pump pushing, not pulling. If not designed, based on this premise, it just won't work properly.
