Emptying tank with a dead macerator

C

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I have been "blessed" with a malfunctioning Groco MPS 600 in the tank macerator. Been into the tank 2 times now and had the luxury of a dockside pump out each time to clear the tank 1st. I had thought the last time fixed the pump, but alas it it time for a replacement. After this weekend I needed to empty the tank (liquid only, fisher"men") after the boat was on the trailer....in prep for the ultimate fix of a new pump motor, seal and rubber housing. I fabbed a quick vent cover to pressurize the tank and push the liquid past the macerator and out the thru-hull. Making sure the head pump was in dry bowl, and the pump out cap was tight, I simply pressurized the tank with compressed air through the vent and pushed the tank liquid through the non functioning macerator and out the through hull fitting into an awaiting bucket. Easy and careful in this process, you can over pressurize the tank and have a real big mess on your hands!! See the pix
 

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Interesting tactic! Your output hose from your tank to the thru-hull... does the hose exit at the bottom of the tank? I've, unfortunately, got some experience (some by choice to figure out easy ways to pump out at home) in this area with my Sundancer, but all fittings in that tank are on the top (I suppose that wards off leaks if a fitting breaks) and I don't think that would work.
 
The Groco macerator referenced is a submersible pump with the pickup at the bottom of the tank. The outlet from this pump goes to the through hull. Even if all of the fittings are on the top of the tank, the pickup for the pump needs to have a tube to the bottom in order to empty the tank.
 
Yes, you're correct there's a dip tube. What I was getting at, though, was I wondering if this process would still work since the pressurized tank would have to push the yucky stuff UP the tube. If it would do that, I wonder how much pressure would be needed?

I have an automatic setup now that I designed for my Sundancer (it's all controlled by a little key fob - just the push of a button does everything). But you peaked my interest with your idea - these are the kind of things I "tuck away for later use"!
 
Trying to think back to my high school physics class... in terms of how much PSI it would take to push the water up a dip tube (say 2"x18")... Did I do my math correctly in that it would only take about 3lbs? If so, that's not too bad - I'd be OK with putting that amount of pressure into a tank (I've done a little more in tracking down leaks).
 
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