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Old 05-11-2016, 11:06 PM   #41
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Yep, no manual pump. Not too worried about it.
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Old 05-11-2016, 11:41 PM   #42
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I look at it like this: 180GPM vs 30-40GPM I say 30-40 because as one gets tired you won't be pumping as much. So as long as the generator is above water we're good. But if it goes beyond that I'll be getting the inflatable raft and cutting the straps on the tender.
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Old 05-12-2016, 01:50 AM   #43
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I look at it like this: 180GPM vs 30-40GPM I say 30-40 because as one gets tired you won't be pumping as much. So as long as the generator is above water we're good. But if it goes beyond that I'll be getting the inflatable raft and cutting the straps on the tender.
Yeah, I suppose. I just haven't caught up with these modern inventions. You know, like electricity....
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Old 05-12-2016, 04:21 AM   #44
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Ericsson safety pump

I've got an Ericsson Safety 3" trash pump on the prop shaft. Always on when propeller is turning. The higher reduction ratio of the gearbox, the less output of the pump....the trash pump discharges almost anything....

Theoretically, mine can deliver around 1200 liters/min.

It can be hydraulic (or electrical) driven too if higher capacity is required...

ESP Ericson Safety Pumps | AES
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Old 05-12-2016, 07:32 AM   #45
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I look at it like this: 180GPM vs 30-40GPM I say 30-40 because as one gets tired you won't be pumping as much. So as long as the generator is above water we're good. But if it goes beyond that I'll be getting the inflatable raft and cutting the straps on the tender.
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Old 05-12-2016, 07:46 AM   #46
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I've got an Ericsson Safety 3" trash pump on the prop shaft. Always on when propeller is turning. The higher reduction ratio of the gearbox, the less output of the pump....the trash pump discharges almost anything....

Theoretically, mine can deliver around 1200 liters/min.

It can be hydraulic (or electrical) driven too if higher capacity is required...

ESP Ericson Safety Pumps | AES
That is a genuine and true emergency pump.
Plus a bilge blower.
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Old 05-12-2016, 08:56 AM   #47
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Yes, it's an all-in-one... always running if propeller is turning...and much cheaper too...no hydraulic or electrical power required.

A downside is that it requires another thru-hull.

Actually, that's where I could have improved my design because my thru-hull is on the hull side, but it would have been better if it was discharging onto the aft deck...
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Old 05-13-2016, 06:19 AM   #48
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Folks that wish to de-water fast might copy what ships do.

Do not waste energy lifting water.

Simply pump it out the bottom.

A remote cabled thru hull would make this EZ.
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Old 05-13-2016, 06:38 AM   #49
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Great setup Oliver.
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Just curious if your Avatar pic was taken at Shipyard in Erie, Pa?
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Old 05-13-2016, 09:31 AM   #50
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Folks that wish to de-water fast might copy what ships do.

Do not waste energy lifting water.

Simply pump it out the bottom.

A remote cabled thru hull would make this EZ.
Does that make a difference? You have to overcome the external water pressure which I would think takes the same energy as lifting the water to the waterline. I haven't tried to do the math so that's just my gut feeling. Lifting above the waterline would take more energy.
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Old 05-13-2016, 01:17 PM   #51
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Dave I don't know why more people don't have a way to easily use their engine pump as a bilge pump in an emergency. I have a tee and valve just before my strainer. A hose runs from the valve down to the bilge. The plan in an emergency is to open the valve on the tee and then close the seacock.

A couple of years ago I was on a sport fish boat that was sinking. I kept looking at the two big Jabscos on the engines wishing there was an easy way to use them. If we hadn't gotten the flooding under control, I'd have been down there with my pocket knife trying to cut those big hoses.
Yep.
I think this is must do first step.
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Old 05-13-2016, 01:47 PM   #52
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Does that make a difference? You have to overcome the external water pressure which I would think takes the same energy as lifting the water to the waterline. I haven't tried to do the math so that's just my gut feeling. Lifting above the waterline would take more energy.
They pump it out the bottom via a stand pipe in most cases. So there is no need for a remote controled valve. Nor are you fighting the rather significant back pressure from trying to pump water out against water trying to come in.
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Old 05-13-2016, 07:53 PM   #53
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They pump it out the bottom via a stand pipe in most cases. So there is no need for a remote controled valve. Nor are you fighting the rather significant back pressure from trying to pump water out against water trying to come in.
So the stand pipe has to come higher than the waterline? How does that reduce how high the pump has to push the water?

I had never thought about it but if you've got a ship with a thirty foot draft or more, you need a serious pump to get water out of the bilge and outside the ship.
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Old 05-14-2016, 06:49 AM   #54
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The pumping head needed at a given flow rate comprises of the differences of geodetic height, pressure and flow velocities, all measured between inlet and outlet of the pipework involved, and the pressure losses of the pipe flow.
If pumping out through the bottom the stand pipe inside of the boat does NOT count into the geodetic head since the pipe outlet is at the same height as the inlet. In that configuration the geodetic head is given by the height of the sea level above the bilge pump while the stand pipe contributes only to the pressure losses of the pipe flow. That is why this pipe work should be designed carefully with appropriate size (as big in diameter as reasonable with regard to installation situation) and avoidance of sharp elbows.
If pumping through the hull above sea level the geodetic head is given by the height of the outlet above the bilge pump. Compared to the bottom outlet configuration the geodetic head is now obviously increased by the height of the outlet above sea level. In addition the pump has now to overcome the parasitic kinetic energy of the water splashing out of the outlet.
But: Whether the pump head needed at a given flow rate is lower with the bottom outlet configuration strongly depends on the pipe flow pressure losses i.e. on the appropriate design and sizing of the pipe work. You need at least two elbows in the stand pipe while you can design the pipe more or less straight forward imposing very small pressure losses in case of pumping out above sea level. So, as usually, it depends all on the installation situation and whether the ER is roomy enough for a reasonable sized pipe work.
There might be other advantages and disadvantages of both configurations beside the pump head question.


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Old 05-15-2016, 07:08 AM   #55
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5 PSI is about an 11 ft head .

Most of our boats do not draw even half of that.

When Practical Sailor tests pumps and uses a 4 or 5 ft discharge height many pumps only see half of their claimed pumping capacity.
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Old 05-15-2016, 08:11 AM   #56
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Emergency Bilge pump installed

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When Practical Sailor tests pumps and uses a 4 or 5 ft discharge height many pumps only see half of their claimed pumping capacity.

... already two elbows will count for those 4' discharge head if we want to pump out 32 gpm through a 1" pipe. We still need 1' discharge head in a 1,5" pipe work with two elbows to overcome the pressure losses, they become only negligible if we increase the inner pipe diameter to 2". Most of us won't have installed such a pipe or hose. And to make it even worse: as a minimum we have to add the height of the sea level above the bilge pump to get the needed head of the pump.
32 gpm is not much IMO. It is more or less the flow rate produced by a failed 1" seacock 3' below sea level ...


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Old 05-15-2016, 08:27 AM   #57
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What about using a 1hp sump pump? They move 4k to 5k gal.hr and are designed to live in a pretty nasty environment.
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Old 05-15-2016, 09:06 AM   #58
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What about using a 1hp sump pump? They move 4k to 5k gal.hr and are designed to live in a pretty nasty environment.
At HomeDepot $230 will buy you 5,500 GPH or 4,680 GPH at 10 foot lift.
Which is 78 GPM, which may not be enough for an emergency.

The Everbilt 1HP cast-iron submersible sump pump equipped with innovative reed sensor vertical float switch pumps to 5500 GPH at 0 ft. lift or 4680 GPH at 10 ft. lift. The rugged cast-iron construction, oil-filled and thermally protected motor, permanent lubricated ball bearings provide long time trouble free service. The unit fits in a 10 in. Dia sump basin.

As opposed to these which I am sure cost a whole lot more.

Global Pump® portable electric submersible pumps are ideal for corrosive and abrasive applications. Ideal for high flow,lower head applications. Available in models from 3" to 8" and 5 hp to 50 hp., these pumps can achieve max heads of 225 ft. and 2300 gpm.
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Old 05-15-2016, 09:48 AM   #59
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It isn't only a question of max flow rate of the pump (of course: the higher the better) but also of the max discharge head of the pump. Both figures indicate start and end of the pump performance curve, max discharge head Hm at zero flow rate and max flow capacity Cm at zero head. As a simple approximation we can assume the pump performance curve as a straight line between those two points which are usually indicated on the data sheet. Therefore the ratios of actual flow rate C / max flow capacity Cm and actual discharge head H / max discharge head Hm are correlated by
C / Cm = 1 - H/ Hm
This crude approximation is on the safe side i.e. it will slightly underestimate the actual flow by some 10-15% in the head region of our interest.
Taking as an example a "heavy duty 12V submersible bilge pump" with 16.5' max discharge head and max flow capacity of 2060 GPH - performance clearly above the standard installations I see on pleasure boats here in the Baltic region. Against 5' head (4' for our draw and 1' for the pressure losses of our 1.5" pipe work at 32 GPM) our nice formula calculates a flow rate of
C = 2065 GPH x (1 - 5'/16.5') = 1440 GPH = 24 GPM.
Even taking into account that our formula might underestimate the flow by 15% - this above standard (at least for the pleasure boats here) pump will not manage to bring the 32 GPM out of our boat.
So take the numbers for max flow capacity and max head of the pump in question and check the expected flow rate against a typical head of 4 - 6(7) ft to make your decision. And please don't forget to adjust the diameter of your pipe work accordingly: if you double the flow rate you need to increase the pipe diameter by the factor of 1.4 to end up with the same discharge head ...


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Old 05-15-2016, 05:50 PM   #60
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The Everbilt 1HP cast-iron submersible sump pump equipped with innovative reed sensor
vertical float switch pumps to 5500 GPH at 0 ft. lift or 4680 GPH at 10 ft. lift.

Assuming two elbows in a 1.5" pipe and the bilge pump 4' below sea level, this AC pump would be able to get those 4680 GPH = 78 GPM out of our boat. The pressure loss of the pipe flow would be in the range of 6', the overall discharge head therefore 10'.
AC pumps might be really a safety plus in an emergency case - we have always an AC pump (with a hose mounted) handy when underway. IMO an AC pump is the only chance we have to control a leak caused by a failed seacock over a longer period of time.



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