Bilge pump arrangements

[[2574]]

I'd appreciate knowing what capacity 12v auto bilge pumps are typically fitted on a medium sized yacht - say 12m LOA. I have a rather pathetic looking 12v plastic jobby that boldly claims 500gph performance, I just don't beleive that. It runs on a 2.5A fuse, I can't see that shifting 2.25tonnes of water every hour, no chance. So I'd like to uprate - but what is typical? I'd like to have something that might do some good in a mild water ingress situation, I realise that a serious water leak won't be dealt with by any 12v pump.

 

[SeaAndSea]

I haven't got an answer, but we have a similar issue on board our Trader47. We have 2 old and feeble looking pumps that I want to replace. New boats of a similar size seem to have 3 or 4 bilge pumps. Can you have to much bilge pump capacity?

 

[[2574]]

I haven't got an answer, but we have a similar issue on board our Trader47. We have 2 old and feeble looking pumps that I want to replace. New boats of a similar size seem to have 3 or 4 bilge pumps. Can you have to much bilge pump capacity?

A member of our Owners Forum has suggested these Whale low profile pumps - they look like a practial solution, maybe more than one deployed could be a good strategy as you say. Have a look: Whale Marine - Products

 

[Rappey]

. Can you have to much bilge pump capacity

Not when your sinking. Bigger the better ?

 

[lenten]

best serious bilge pump-----jabsco --belt driven off the engine

 

[Refueler]

500gph .... 1200gph ..... all relative to how high it has to pump out to exit .... how high the water level the pump is in ...

Those stated figures are basically free pumping rates ....

I have had 500 and 1200 rated in same position in my main bilge .... noticed any difference ? NO !! Pumps have been same physical size in fact ... rate of flow exiting overboard seems similar visually.

To combat a leak ?? Reality check I think ... the rate water comes in can easily overwhelm even a large pump. Lets assume your speed log suddenly decides to eject itself .... you'd need a good pump to keep up with that ... (I know wood plug is called for) ... but I'm just trying to illustrate rate of water.

 

[alan_d]

The gph figures quoted are usually against a tiny head. Once you start lifting the water to any reasonable height the gph figures fall off steeply. Also, the gallons referred to are usually US ones (smaller than imperial) .

 

[Martin_J]

As well as the smaller electric bilge pump of a similar size to what you mention, I installed the Johnson L4000 (4000gph) because it has a 1.5" outlet pipe.

I figured that if I had a 1.5" through hull hole that might accidentally let water in, I ought to have the same size hose through which to pump the water out. It's coupled to a Johnson Ultima switch so no moving parts in the switch. Easy to test with a damp finger across the face of the switch.

All the smaller pumps seem to only have 3/4" outlet so they just don't seem right.

These are in addition to the two manual pumps (one of which can be operated from inside with all hatches closed and one from outside) and they all have their own independent outlets.

Problem with fitting the L4000 pump was that most panel mount bilge pump switches are not rated for 25A so choice is limited.

 

[Martin_J]

The Johnson L4000 will also take a 2" outlet hose if needed... That would have been a lot more trouble routing the outlet hose from bilge to stern.. maybe one day.

 

[Refueler]

I had the Water Witch solid state pump switch ..... it lasted a few years but was unreliable TBH. I gave up with it and reverted to a simple float switch type pump.

I also gave up paying silly money for name brands - as they were no better than the cheapo chinese ones on eBay.

I've mentioned this in other threads .... I also added to my 'portable' inventory .... an aquarium pump .... sounds daft - but its very good for clearing out those awkward areas ..... there are 12v and 240v types ....

 

[Daydream believer]

The gph figures quoted are usually against a tiny head. Once you start lifting the water to any reasonable height the gph figures fall off steeply. Also, the gallons referred to are usually US ones (smaller than imperial) .

But the head of most is quite low anyway. Many have the outlet in the transom or similar & the head is probably less than 1200mm on a 40 ft boat.
The real issue must be how long the batteries can maintain the current to a bigger pump. If one gets a short in the engine wiring & cannot start it to charge the batteries( can easily happen if the boat rolls, sloshing water everywhere)
One can have a massive pump, but if it drains the batteries in a few minutes it is of little use. Except it may make access to the leak possible for a very short while.
What sort of current does a pump draw? Is it high enough to be an issue & can one switch all the batteries into one bank to feed it long enough to save the day.
I am told bread bins use less current & shift a fair amount of water, if in the hands of a drowning man

 

[Daydream believer]

I've mentioned this in other threads .... I also added to my 'portable' inventory .... an aquarium pump .... sounds daft - but its very good for clearing out those awkward areas ..... there are 12v and 240v types ....

In reply to your solution
I have upgraded the shower pump on my boat because the original was useless & the new one( whale gulper) does not need a filter & can be run dry. In doing this I inserted a hose lock fitting in the line just before the pump. I now have a long 18mm hose with a hoselock fitting, that I can quickly connect to the pump.
I have drilled an 8mm diameter hole in the floor just above the lowest point in the bilge.I did this in one of the dark lines so that it is hardly noticeable.
On the end of the long hose I have reduced it to a 12 inch length of 7mm copper pipe.

Now I can poke this through the hole vertically & because the diameter is so small it will suck up water to a depth of .5mm. This avoids the hassle of raising the floor. I can also move the end of the hose around the boat ie under the engine where the vacuum valve drips & "hoover" up very shallow amounts of water

If I did have a leak that was too much for the existing pump I could pull the copper pipe off the end of the hose & that would give me some extra capacity via the shower pump. It would not cope with a leak from a hull seacock failure.
However, I doubt that would be quite as bad as suggested. If it were a split in the hose the one would shut the valve. If, as has happened to me, ( on dry land I might add) the metal betwixt cock & hull broke then that would not just burst free. It would start with a split & water would be seen in smaller quantities first. That would prompt investigation. I am sure that remedial attempts could be undertaken fairly quickly. For instance, if really bad,. One would have a plug ready ( Mine hang by each outlet). Then bash the fitting off completely & ram the plug home.
I have over the years had quite bad collisions with unseen objects. In one it smashed the steering oar from my Aeries & many will know that they are built like the proverbial brick s..t house. I have had a number of chips in the coppercoat. & a lump out of the rudder. All submerged objects.
So that would be the biggest worry & I doubt that even the biggest pump would be any good in a hull puncture. Perhaps a hull crack where the hull sprang back into place but allowed water in. That would be a problem.
However, I think that the OP is over thinking the issue unless going blue water sailing among the reefs of uncharted islands.
One should have the option of a good manual pump as well

 

[Porthandbuoy]

I fitted the highest capacity electric pump that would physically fit in the bilge. A Rule 3700 and a float switch. Yes, it draws a lot of amps, but it should give me time to track down and plug a biggish leak if I’m on board.
If I’m not on board, no bilge pump on earth would stop her going down if a through hull fitting were to fail.
When I get aboard I check the battery state of charge monitor. It’s usually 95~100% (no solar panels yet). Anything less and I’d suspect the pump’s been kicking in and would investigate.

There’s also a Henderson mk5, a portable manual and a portable electric pump.

 

[Stemar]

What is a bilge pump for? If it's to keep you from sinking after hitting something, you're going to want something between big and HUGE. Unless your battery bank is the size of Uma's, that means engine driven, and still plenty of but what ifs.

For nearly all of us, nearly all the time, it'll either never do anything, or it'll deal with that annoying leak, when a smaller one will be fine. Even if you have that engine driven monster, you'll still want an automatic electric one, because the big 'un will wait patiently for you to turn it on as the water rises... Yes, if you get a leak when you aren't on board, it'll run the battery down, but better to be dry with a dead battery than have a bunch of water damage.



I have one of these in each hull

As the water traps in both exhausts leak (a project for this winter), they earn their keep, and they do it fine.

When I get aboard I check the battery state of charge monitor. It’s usually 95~100% (no solar panels yet). Anything less and I’d suspect the pump’s been kicking in and would investigate.

A neat trick I read many years ago was to put an analogue 12v clock in parallel with the pump. If it says anything other then 12:00, the pumps have run, and you know how much. Obviously that requires a separate float switch. Can you still find that kind of clock

 

[geem]

500gph .... 1200gph ..... all relative to how high it has to pump out to exit .... how high the water level the pump is in ...

Those stated figures are basically free pumping rates ....

I have had 500 and 1200 rated in same position in my main bilge .... noticed any difference ? NO !! Pumps have been same physical size in fact ... rate of flow exiting overboard seems similar visually.

To combat a leak ?? Reality check I think ... the rate water comes in can easily overwhelm even a large pump. Lets assume your speed log suddenly decides to eject itself .... you'd need a good pump to keep up with that ... (I know wood plug is called for) ... but I'm just trying to illustrate rate of water.

Many years ago I did the calculations. For a boat with a 2" hole a metre down (worst case scenario I could think of) you need to be able to pump 20,000 litres per hour. I did the calculations for the the surface roughness of my bilge pump discharge pipes and vertical head. I have four pumps on automatic float switches. The main bilge pump is a Rule 2000gph( US gallons). The shower pump is the same. The engine room pump is 750gph and the emergency pump is 3700gph. In addition I have a smaller roving pump that is 500gph. With the automatic pumps I can achieve 19,000litres per hour, theoretically allowing for pipe friction and head. I would need to start the engine or generator to keep battery voltage up to run all these pumps. In addition, we have an alarm on the main sump pump that sounds when the pump runs. This pump is located in the lowest part of the boat.

 

[[2574]]

Many years ago I did the calculations. For a boat with a 2" hole a metre down (worst case scenario I could think of) you need to be able to pump 20,000 litres per hour. I did the calculations for the the surface roughness of my bilge pump discharge pipes and vertical head. I have four pumps on automatic float switches. The main bilge pump is a Rule 2000gph( US gallons). The shower pump is the same. The engine room pump is 750gph and the emergency pump is 3700gph. In addition I have a smaller roving pump that is 500gph. With the automatic pumps I can achieve 19,000litres per hour, theoretically allowing for pipe friction and head. I would need to start the engine or generator to keep battery voltage up to run all these pumps. In addition, we have an alarm on the main sump pump that sounds when the pump runs. This pump is located in the lowest part of the boat.

Suddenly I feel very inadequate with my little 2.5A fused 500gph (supposedly) plastic win-at-a-duck-shoot pump jobby……another project crystallises before my eyes……

 

[Daydream believer]

Many years ago I did the calculations. For a boat with a 2" hole a metre down (worst case scenario I could think of) you need to be able to pump 20,000 litres per hour.

I would suggest that a 2 inch diameter hole by 1 M head of water would be a fraction under 15000 litres per hour
I think that if one decided to google there would probably be a few flow calulation programmes available to demonstrate this. They may all vary a bit. But not by much. Should back my figs up -- I hope
?

 

[geem]

Suddenly I feel very inadequate with my little 2.5A fused 500gph (supposedly) plastic win-at-a-duck-shoot pump jobby……another project crystallises before my eyes……

I didn't have to do much to upgrade my pumping system. We just added the Rule 3700gph pump. All others were fitted. This pu,p has a 1.5" outlet and moves some serious water.
We sail as a couple. My thoughts were that if we started to take on water I would want to know straight away and not wait for a high level alarm to activate. Having the main bilge pump activate a sounder every time it operates works for me. We only get worried if it doesn't stop. I would want to be looking for a leak ASAP and not have the floorboards floating. We don't have a fixed manual pump. With just two of us onboard I don't want half the crew pumping whilst we try and deal with an influx of water. We would need both of us on the case. We do have a stirrup pump that we can use for pumping out jobs but it's not designed to empty the boat of water.
If we get a skin fitting failure of say 1.5" diameter a foot below the water then we should easily be able to cope with electric pumps whilst we plug the hole. Interestingly that failure is quite possible in a smaller boat than ours. The difference is that we take longer to sink due to our higher hull volume than the same size hole in a smaller volume hull.

 

[geem]

I would suggest that a 2 inch diameter hole by 1 M head of water would be a fraction under 15000 litres per hour
I think that if one decided to look there would probably be a few flow calulation programmes available to demonstrate this. They may all vary a bit. But not by much. Should back my figs up -- I hope
?

I would suggest that a 2 inch diameter hole by 1 M head of water would be a fraction under 15000 litres per hour
I think that if one decided to google there would probably be a few flow calulation programmes available to demonstrate this. They may all vary a bit. But not by much. Should back my figs up -- I hope
?

Yes, I think I assumed a skin fitting could be pushed out by a collision with something. The log would be the riskiest thing on oue boat being plastic and infront of the keel so I must of assumed slightly bigger.
Just found a calculator and it says 57mm for 20,000l per hr. Not much bigger. Anyway, it's a little academic. I think the most likely failure is a toilet hose or engine inlet hose that would not be so deep so probably a 1.5" hole a foot down. I think we are covered?

 

[Refueler]

"geem' is close to what I consider the factors ......

But I am not looking for a situation to 'match or near equal' water in ... my idea is to stop the water as fast as possible .... a bin liner under a planing hull can slow water to a trickle - its how we used to salvage boats in fact ... water pressure pushes the liner into the hole ... as long as lines are holding the corners - you now have a lot more time to work.
Dinner plate and a load of cabin gear pressing it onto the hole reduces water in ...

The trick is to INCREASE the time you have for pumping out by reducing the water in. That also makes your low volume pumps do the job ....

When it really goes against you and you have time - run the b***** boat aground or up against a wall ....