Bilge pump: automatic or non-automatic?

An automatic bilge pump could give you a false sense of security if you have a persistent leak. Your bilges will be dry and you will be quite happy until that persistent leak gradually gets worse, the bilge pump runs constantly, and the battery goes flat. Such a failure mode can be attributed to stern glands, hoses and skin fittings. I prefer keeping an eye on how much, if any, water is in the bilge sump so I can monitor the rate of ingress.

Last season I was on the cusp of hauling out mid-season to fix a worsening leak around the shaft tube. An automatic bilge pump could have left me oblivious to the problem until I had a major leak. A high-level alarm has a lot of merits, especially if it incorporates a flashing light visible when the boat's on her mooring.
 
Sailingsaves said:
A FLOATING log or other flotsam or jetsam, hitting and holing your boat ( as you seem to think you are invulnerable to any water ingress).
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Ah, I thought you were talking about the log transducer falling off and causing a leak. The ingress of water from a floating log (or indeed a missing log transducer) would be more than the vast majority of bilge pumps could cope with. That's where the liferaft comes in handy...
 
geem said:
Bilge pumps are rated at zero head so a Rule 3700gph (yank gallon) will do 2450gph at 2m head.
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In ideal circumstances - ie smooth full-size pipe, no restriction where the pipe fits the skin fitting, 10-hours of running-in, and 13.6v supply (so the engine has to be running). A number of tests have shown that real-world results are less than the manufacturers state.
 
Sailingsaves said:
.....

Oh, and my 2700 Rule pump is so powerful it could almost work as a bow thruster if stuck on a stick and held be crew.
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This place has been taken over by idiot dreamers.
I don't see a 2700 in the Rule catalogue, but the 3700 draws 12.2A at 13.6V, that's 166W in the real world.
 
Porthandbuoy said:
An automatic bilge pump could give you a false sense of security if you have a persistent leak. Your bilges will be dry and you will be quite happy until that persistent leak gradually gets worse, the bilge pump runs constantly, and the battery goes flat. Such a failure mode can be attributed to stern glands, hoses and skin fittings. I prefer keeping an eye on how much, if any, water is in the bilge sump so I can monitor the rate of ingress.

Last season I was on the cusp of hauling out mid-season to fix a worsening leak around the shaft tube. An automatic bilge pump could have left me oblivious to the problem until I had a major leak. A high-level alarm has a lot of merits, especially if it incorporates a flashing light visible when the boat's on her mooring.
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We always have water in our bilges for the last 8 years we've owned the boat - getting a float switch finally reached the top of the list of jobs last year and it's been great. When it's quiet on board we can hear it going on and off so it's a good test of how much water is appearing and we tend to switch it off when going to bed to avoid it disturbing us all night.

When we leave the boat afloat for up to 4 months without visiting it's left off as it would drain the batteries and a serious seawater leak would sink the boat pump or no pump.
 
The automatic 'cycling' pumps seem to work well for owners of open boats. More reliable than float switches. RIB owners like them, to pump the rain out. But they are not intended to be fired up dry every few minutes for months on end(AIUI, the bearings need water), so have no place in a modern yacht.
If you must have an automatic pump, then a normal float switch is better in a yacht.

But if you pump any oily water into the river, I will be the first to report you and cheer if you get a four-figure fine.
 
pvb said:
Electric bilge pumps are rated usually at zero head and (often) 14v supply. In the real world, with discharge head, outlet pipe friction losses and lower voltage, their performance can be disappointly low.

With decent regular maintenance, I'm not sure how a "log or something" might suddenly cause a substantial leak. But if you sleep soundly with your 5 bilge pumps, that's fine.
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A floating log in a river estuary could have substantial momentum and damage a skin fitting if you're very unlucky.
 
pvb said:
In ideal circumstances - ie smooth full-size pipe, no restriction where the pipe fits the skin fitting, 10-hours of running-in, and 13.6v supply (so the engine has to be running). A number of tests have shown that real-world results are less than the manufacturers state.
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If you were sinking why wouldn't you start the engine? We could run the generator but even without 1000 amp hr of domestic battery helps whilst you find the problem. Our skin fittings are 1 1/2" for the Rule 3700. The two 2000 GPH have 1" fittings. The engine 500 GPH pump has 3/4" fitting. Pipe is all smooth bore high spec oil resistant hose. Battery box is completely water proof for two foot above cabin sole then will slowly leak through joints in sealed 10mm Perspex lid. If water gets to this point then the 1m down from water level in the cabin to any hole in the hull is going to be incredibly difficult to stop. The generator is elevated 2ft above the cabin sole so should still charge batteries
 
Is there a single documented case of a GRP yacht being kept afloat by its own automatic bilge pumps?
Or a GRP yacht sinking which would have been saved by a 12V Rule pump?

I've logged some miles on wooden classics which don't have self draining cockpits. I've raced 60+ year old boats which 'work' a little. Bilge pumps earn their keep on such vessels.
 
lw395 said:
Is there a single documented case of a GRP yacht being kept afloat by its own automatic bilge pumps?
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Many GRP boats don't have 100% dry bilges, so a bilge pump is important to keep the bilge water to a minimum.

As for floating logs punching holes in the hull, methinks not. As for the Rule type pump stopping a boat with a hole in the hull from sinking, not a chance unless it's a pin hole.
 
PaulRainbow said:
As for the Rule type pump stopping a boat with a hole in the hull from sinking, not a chance unless it's a pin hole.
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Indeed, my bilge pump with float switch saved my boat a couple of years ago when I ended up with 3mm hole right though the bottom of one hull.

Having the pump running throughout the night (zero sleep that night!) at least gave me time to review and consider all the options once daylight returned. :ambivalence:

Richard
 
RichardS said:
Indeed, my bilge pump with float switch saved my boat a couple of years ago when I ended up with 3mm hole right though the bottom of one hull.

Having the pump running throughout the night (zero sleep that night!) at least gave me time to review and consider all the options once daylight returned. :ambivalence:

Richard
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Ok now tell us exactly what you were fitting to the boat's hull when the drill went through?
 
PaulRainbow said:
Many GRP boats don't have 100% dry bilges, so a bilge pump is important to keep the bilge water to a minimum.

As for floating logs punching holes in the hull, methinks not. As for the Rule type pump stopping a boat with a hole in the hull from sinking, not a chance unless it's a pin hole.
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A 1 1/5 inch skin fitting, say an impeller fitting failing due to collision may leave a 2" hole on the boat. 1m down that will flow 20,000 litres per hour. Doing the calc, taking in to account the head losses for how far you pump up will tell you how much you need to pump to match the loss or at least reduce the fill rate of your hull to buy you some time. Rule type pumps can easily be sized to give you a decent flow rate. Compared to a manual pump, they allow the crew to search for the leak. If you sail singlehanded or as a couple you don't want all the crew or half the crew to be pumping whilst the boat sinks. You need to find the leak and fix it. We have five Rule type pumps four are automatic.
The smaller your boat the quicker you sink so perversely, the small boat really needs more pumping capacity than a larger one for the same 2" hole 1m below the surface
 
RichardS said:
Jeez .... that looks like a lot of 3mm's. :ambivalence:

Richard
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Just think of the moment when he stood back inside the boat, really proud of his new flooring. And the look when the boat came out of the water (weeks, months later looking at the corrosion) and he found out what that niggling water leak was.
 
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