"Huge" is such a subjective word. We use stuff in the 12,000 gpm range occasionally for work. Folks, when the power you're putting the pump is higher than the energy from the CPU you're chasing down the wrong pathway.

I've got a "little" pump I use at work that's rated for ~55' TDH at 10 gpm. It only cost $228 with OEM discount (230VAC/3ph, single phase available). It has 1-1/4" suction and discharge ports. If anyone thinks such a pump has a place in watercooling a PC, they are sadly mistaken. Nonetheless, it's available from Gorman-Rupp as an off-the-shelf item. Just check out their "ATM" line of pumps.

I'm seriously thinking of using the single phase version for a hefty pond project.

Anyone asking about how to fit one of these into a watercooled PC is either nuts or has no idea what they are doing.

Oh, and you're wrong Bill. I just served up cheese, crackers, and sausage to all the co-workers to celebrate a new product launch (our third kid arrived Nov 20). May not be up to your standards of "lunch", but hey, I'm cheap and it was my nickel. LOL.

correction accepted, and congrats

Exactly...!!!
No, the quoted price is not a typo... (this pump was designed for industrial apps)
And No, IMHO this pump is not suitable for even a radical water-cooled PC... :) (a 1/2 HP prime mover vs. ~100 watt CPU... NOT)

Congrats Dave!!! :D :) :D

Yes, congratulations on the new child Dave. Our second child arrived on the 1st December as well, so I'll crack open a pack of dips and crackers too I guess.

That's rather disappointing. A 1/2 HP motor is plainly silly.

I guess what I'm thinking of may not be possible? Basically would've liked to have seen a pump that will provide about 5m of pressure drop at 10LPM (~2.7gpm) for as little wattage as possible. Peak pressure head of say 8m or so. Peak flow of around 15LPM (4GPM) or so. Power consumption in the ~16W mark. Physics says it's doable (only ~8W of actual work being done to achieve such PQ characteristics), but I guess I don't understand enough about pumping efficiency to understand why such cannot be practically done, or perhaps it is more of a manufacturing/cost issue?

Well a reciprocal congratulations is in order. :)

As to the rest of the post, centrifugal pumps need to be reliable and cheap. Efficient isn't too high on the priority list, especially for pond pumps.

You can get industrial pumps in excess of 80% efficient, but they have large diameter, low clearance impellers. Most of the stuff I use requires self-priming ability and needs to deal with solids. These open-vane impellers crap out in the 40-60% efficiency range.

You may be better served going with a fixed displacement pump. Homeboys would simply hack up an old lawn mower engine to get the job done. Some of the little units on pressure sprayers would also do, but the seal friction may be higher than desireable. Then again, IIRC the seals are loaded by the water pressure, so maybe not so bad at modest pressures. None of these solutions is as cheap as a good pond pump.