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I'm looking to build myself a cheap water fountain that filters out gunk for my cat. Here is how it will work (I think)...

Diagram

Anyway just wondering if the pump has to be submerged in water in order for it work properly. I was hoping not because the bowl is fairly small and doesn't need to be huge.

So do submersible water pumps need to be submersed in water to function properly?

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A submersible water pump will operate when not submerged, but running dry will usually reduce the life of the pump because the water is typically the cooling source for the pump.

So my answer to your question would be Yes.

Might I suggest looking at Pioneer Pet #3026A 12V Pump & Transformer, which appears to be an inline pump. But I think you may have more challanges. Pet fountain systems are not usually filtered. Having a filter usually requires a stronger more costly pump...so most inexpensive pet fountain system I have seen just circulate the water.

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  • $\begingroup$ Of course if you want to prolong life of the pump, providing cooling - the submerging/cooling water and the pumped water don't need to be the same water :) $\endgroup$ – SF. Jan 23 '17 at 13:49
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That's not the problem here. You would need to put the filter ahead of the pump, as is done in any aquarium setup, or the pump itself will clog.

That said, you absolutely should be changing the cat's water at least once a day, so worrying about minor dust or gunk is irrelevant.

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  • $\begingroup$ I do change it at least twice per day. He is a young kitten and thus eats (and drinks) quite a bit throughout the day. As for the filter system I should have the filter before the intake? I guess that makes more sense so I don't clog the pump internally. As for my question does it need to be submerged or as long as water goes through it should work? $\endgroup$ – Sie Jun 19 '16 at 0:34
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Basically the two types of pump that are appropriate for this application are the centrifugal pump and the displacement pump. Both types can be submerged.

The displacement pump uses small chambers built into a rotating disk. When operating, the action creates suction on one side, often allowing several feet of water to be LIFTED and ejected. Displacement pumps such as the FloJet series do not need to be submerged and can be located some distance from the liquid.

The centrifugal pump requires fluid to fill the vane chamber, without air. These work by spinning an impeller at high speed, creating a pressure difference between the fluid at the centre of the vane and the outer edge. The low pressure at the inlet draws fluid into the chamber, but any air present will disturb the vacuum. Centrifugal pumps generally have a higher flow rate and operate at much lower pressures than displacement pumps.

So for the water dish, if you can guarantee that there will always be water for the pump to work with, the centrifugal pump would be least expensive, quieter and reasonably reliable. If the dish runs dry, the pump could become damaged, so a method of detecting the water level would be required.

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