Trayson's 2008 XLV ballast system upgrade

[gregski]

The most scientific test I've seen documented was over at centurioncrew. I posted the summary here: https://forum.moomba.com/showthread....104#post232104 His motivation was to study the effect of the sprinkler valves (and removing the internal springs) but he also tested with a brass shut off valve which is more relevant since it would add a little more resistance but not much overall and is probably representative of the loss going through the various couplers and connectors in a typical system.

Here are the results for the Johnson Ultra Ballast pump:
Advertised @ 13.7 GPM or 822 GPH
Unrestricted Test: 13.5 GPM or 810 GPH
1” brass 12 vdc valve: 12.5 GPM or 750 GPH

Here are results for the Tsunami 1200 aerator pump:
Advertised @ 20.0 GPM or 1200 GPH --- Actually should be 1100gph or 18.3gph @ 12V for comparison
Unrestricted Test: 13 GPM or 780 GPH
1” brass 12 vdc valve: 7.5 GPM or 450 GPH

For starters, all of the aerator pumps only perfermed at about 70% of their spec in his unrestricted test (3' of 1.25" hose only). Then, as soon as you add some more resistance in the form of a shut off valve, the aerator performance drops to <40% of the spec number. The impeller pump? It lost about 8%.

while there may be some efficiency loss with the aerator going uphill to the sacs (??)

The loss isn't due to efficiency, it's just a fact of the pump design that the manufactures tell you about.
Here's the spec sheet for the Tsunami: http://www.attwoodmarine.com/userfil...bilge-spec.pdf
Their spec is 1200 gph @ 0' and 900 gph @ 3.3' of head. (0 gph at 11') -> 25% loss in flow (and remember the "real world" performance is probably half of their spec)
And a spec sheet for the Johnson Ultra Ballast: http://www.pumpvendor.com/media/john...690_series.pdf
Their spec is 822 gph @ 0 psi and 810 gph @ 1.4 psi -> 1.5% loss in flow, almost nothing
(note: 1.4 psi = 38.8 inH2O or 3' 2.8" so these are comparing the same thing).
The Johnson pump doesn't lose flow rate but it does increase current draw. The aerator loses flow but uses the same current. Pump design is a trade off.

Combining the data, I would estimate that the real world flow of the Johnson pump would go from about 750 gph to 743 gph as an 1100# sack fills (to 24" high). Likewise, I estimate the Tsunami would go from 450 gph to 383 gph.
I used the 1" brass valve test as a starting point to represent the real world head loss and then calculated 60% of the change of flow due to head loss at 39". Note that this is all based on pumps installed such that they have to pump the output water upwards against gravity. It would be a totally different thing to use one "over the side" where the pump is held above that ballast bag. Flow would probably be close to the "unrestricted test" or better if you actually set up a bit of a siphon.

Overall, my point is there's much more to real world performance than a spec like "1200 gph" but I do believe the available impeller pumps are faster than aerator pumps. They are also more expensive.