Isolate electrics or leave bilge pump on stand by.

[Contest1]

Looks like there,s a majority in favour of leaving the bilge pump live, tho some of the posts for total isolation make good sense

Sorry to those who found the poll or OP unclear. It was meant to get clarity on wether leaving the bilge pump on auto or standby was common practice.
Seems it is.

 

[lynall]

Pretty certain its a condition of my insurance to have an auto bilge pump fitted, mines hard wired straight to the battery via a fuse.



Lynall

 

[maby]

But that all depends on the leak! Almost any bilge pump will cope with a dribble, but no electric bilge pump will win against a serious leak.

I don't think it depends particularly on the speed of the leak - unless you have some kind of trickle charging system on the boat. The pump will draw a fixed current while it is operating and will shift a known volume of water per hour - if you divide your battery capacity by the current drain and multiply by the number of gallons per hour, you get an approximate volume of water it can shift on your battery pack. It would be interesting to see if that is enough to sink an average sized yacht!

 

[pvb]

I don't think it depends particularly on the speed of the leak - unless you have some kind of trickle charging system on the boat. The pump will draw a fixed current while it is operating and will shift a known volume of water per hour - if you divide your battery capacity by the current drain and multiply by the number of gallons per hour, you get an approximate volume of water it can shift on your battery pack. It would be interesting to see if that is enough to sink an average sized yacht!

Of course it depends on the speed of the leak! If a hose comes off a seacock, it's highly unlikely that an electric bilge pump would keep pace with the water inflow. Pump capacities are always quoted at zero head and free flow; in the real world, pump output is much, much lower.

 

[maby]

Of course it depends on the speed of the leak! If a hose comes off a seacock, it's highly unlikely that an electric bilge pump would keep pace with the water inflow. Pump capacities are always quoted at zero head and free flow; in the real world, pump output is much, much lower.

But that was not the question - certainly there are leaks that are too fast for the pump to cope, but we had been discussing if, in the case of a slow leak, the maximum quantity of water the pump/battery combination can shift would be sufficient to sink the boat. If, for the sake of argument, the battery bank was only able to run the pump for long enough to pump out fifty gallons of water and that fifty gallons in the bilges would not be enough to sink the boat, then you may as well leave the pump disconnected - it is not going to save your boat and may unnecessarily kill your battery.

 

[pvb]

But that was not the question - certainly there are leaks that are too fast for the pump to cope, but we had been discussing if, in the case of a slow leak, the maximum quantity of water the pump/battery combination can shift would be sufficient to sink the boat. If, for the sake of argument, the battery bank was only able to run the pump for long enough to pump out fifty gallons of water and that fifty gallons in the bilges would not be enough to sink the boat, then you may as well leave the pump disconnected - it is not going to save your boat and may unnecessarily kill your battery.

I'm sorry, but you responded to my comment that it depended on the speed of the leak. My comment was made (post #18) in response to jwilson's post "It would be interesting to know how much water a typical bilge pump could shift before it flattened (for example) 200Ah of battery capacity. I do not believe it would be nearly enough to sink the sort of boat that had 200Ah of battery capacity." Regardless of battery capacity, if a leak lets water into the boat faster than the pump can chuck it overboard, the boat will sink. So, as I said, it depends on the speed of the leak!

 

[maby]

I'm sorry, but you responded to my comment that it depended on the speed of the leak. My comment was made (post #18) in response to jwilson's post "It would be interesting to know how much water a typical bilge pump could shift before it flattened (for example) 200Ah of battery capacity. I do not believe it would be nearly enough to sink the sort of boat that had 200Ah of battery capacity." Regardless of battery capacity, if a leak lets water into the boat faster than the pump can chuck it overboard, the boat will sink. So, as I said, it depends on the speed of the leak!

We are still talking cross purposes here. Certainly, there are leaks that will sink the boat irrespective of whether or not the automatic pump is running, but the original focus of this thread was someone who's batteries had been destroyed by a faulty pump switch that had allowed the pump to run them completely flat. That then developed into a discussion of whether or not there was any point in leaving the pump turned on and risking it killing your batteries. And that, in turn, became a discussion as to whether or not the volume of water that the pump/battery combination can shift would be enough to sink the boat. Provided the leak is not so fast that it overwhelmes the pump, the speed of the leak does not impact on the quantity of water the pump/battery combinatoin can shift before the battery goes flat. It had become far too academic for the speed of the leak to be relevant!

 

[pvb]

Provided the leak is not so fast that it overwhelmes the pump, the speed of the leak does not impact on the quantity of water the pump/battery combinatoin can shift before the battery goes flat. It had become far too academic for the speed of the leak to be relevant!

Just trying to follow your logic here. You're saying as long as the leak isn't too fast, its speed isn't relevant. To my mind, that means the speed of the leak is relevant.

 

[maby]

Just trying to follow your logic here. You're saying as long as the leak isn't too fast, its speed isn't relevant. To my mind, that means the speed of the leak is relevant.

Well, ok - but not in the way that your post seemed to imply. If you start with a trickle and gradually increase the speed, the quantity of water that the pump/battery combination can shift remains essentially the same until you reach a speed of leak that exceeds the speed of the pump - at that point the basis of the calculation changes - there will be a leak speed for which the pump is still running as the boat finally sinks and (presumably) the battery will not go flat because the whole thing will be at the bottom of the sea.

 

[Contest1]

Thanks for all the input.
Just bought a Water Witch 101 pump switch and plan wireing it in at the weekend.
Manufacturer claims it will not react to a fuel or oil spill.

 

[Stemar]

+1 Also if you have bildge pump how do you know if she is leaking? The pump runs and unless it has a smart counter (if one exisits) how do you know the boat is not leaking??

If the boat does develop a fast leak what are the chances of the battery lasting out till you find out?

One dodge I heard of was to wire up an analogue clock from a car breakers in parallel with the pump. Set the hands to 1200 and you've got an instant readout of how long the pump ran for. A digital version would work too, as long as it had a non-volatile memory. I suspect a nose round ebay would find a Chinese gizmo that would do the job for less than the breakers would charge.

 

[nimbusgb]

I put together a YAPP project to monitor a bilge pump and boat batteries for exactly this purpose.

It checked pump run times, automatically tested the pump on a schedule, monitored the float switch and a few other bits and pieces.

Sent messages to a cellphone by sms when certain things were out of whack.

Anyone interested in reviving the project?