How Long Will Your Bilge Pump Last in Emergency?

[a64pilot]

The 4152 gallons an hour is over 35,000 lbs of water, does an average 30 footer have that much buoyancy?
I don't think the water ingress would slow as it sinks, it would speed up wouldn't it?

In the above scenario it's almost over anyway, water is high enough to have shorted out the only real bank, you have no way to generate any electrical power and you have a half dead starting battery, your hosed.
Even if you had 14V to run the pump and you don't and even if you had wiring sufficient to carry the required current and you don't, you are still taking on water at the rate of 15,000 lbs an hour.

Your best move at this point I think is to not play any games, but to start signaling for help and gathering supplies that you want it's the water or hopefully life raft with you.

[Steadman Uhlich]

hi PETE7.

I think I understand your points. What follows is written in a friendly tone of conversation, not an argumentative one.
____________

The GPH for the 2" hole in the boat (3' under MWL) was something posted earlier in another thread (I think by Gord May), and which I had in my notes. Somewhere I have a chart that shows different size holes and the amount of water flow at different depths (originally posted on BOATUS site as I recall).

In any event, the point of my "numbers" (4,000GPH) was primarily to point out that a lot of water is coming in quickly, so available TIME is limited.

As I see it, the most important aspect of this scenario is lack of TIME. How much time can one reasonably expect to have or gain by depending upon a suggested electric bilge pump and a single used battery?

My opinion, based on a lot of reading of reports of sinkings, is "not enough time to find and fix the problem/leak."

I really don't expect an exact or answer or a test from a lab.

So why ask the question?
I think sailors should consider that question (How much time will I realistically have?), prior to putting their faith into a system(s) that looks good on paper, but may fail for possibly unforeseen reasons (some of which are in this scenario).

Similarly, the published specs for a pump have to be weighed by those other factors that are mentioned in other "bilge pump" threads, such as the type of hose used, the friction resistance of the hose material, the head height (how high the water must be lifted to exit the boat), and such.

What I find striking in most of the reports I have read about boats sinking, is that there was little time, and that despite having some bilge pump(s) on board the boat, it was inadequate, or they failed to operate long enough (the pumps stopped working, due to clogs or loss of electric power). This would be expected in a disaster where a boat was compromised by a collision, but when it is from a failed seacock or hose (say 2") it is something we can more closely calculate or anticipate. I have read numerous times over the years where a boat owner reported something like this:

(Paraphrased example)
"I went below to find water up above the sole. I searched for the source but could not find it. I started the bilge pump, but it quit soon after I started it. I could not start the engine. We lost all electrical power within a few minutes. The radio did not work. I decided to abandon ship."
___________

Using an "almost worst case scenario" I chose to write the challenge scenario with a single used battery that had already been used 8 times in attempts to start the engine. So, it is a possibly weak or unknown point (not a fresh/new/fully charged battery). And, rather than saying "1200amp battery bank" I chose a single battery, because every boat with a Diesel will have one of those.

[Steadman Uhlich]

Originally Posted by a64pilot

The 4152 gallons an hour is over 35,000 lbs of water, does an average 30 footer have that much buoyancy?
I don't think the water ingress would slow as it sinks, it would speed up wouldn't it?

In the above scenario it's almost over anyway, water is high enough to have shorted out the only real bank, you have no way to generate any electrical power and you have a half dead starting battery, your hosed.
Even if you had 14V to run the pump and you don't and even if you had wiring sufficient to carry the required current and you don't, you are still taking on water at the rate of 15,000 lbs an hour.

Your best move at this point I think is to not play any games, but to start signaling for help and gathering supplies that you want it's the water or hopefully life raft with you.

Thank you for adding that comment to the discussion.

You and I do think alike on some things.

[Steadman Uhlich]

Originally Posted by boatpoker

Using Bernoulli's formula I come up with 8,166gph for a 2" hole, 3' below the waterline.

Thanks for posting that.
I don't mind being corrected anytime.
I know mistakes can happen, and I do want to post accurate numbers, but often refer to others more knowledgeable for some facts/numbers/calculations and I don't claim to be an expert on bilge pumps.

I should have double checked the numbers I quoted, by using a second source, rather than just one.
_______________

Where did I get that number?
I read it in an earlier post on bilge pumps. It appears to be incorrect.
___________

CORRECTION!

Earlier I used the 2" hole at 3 foot depth = 4,152 Gallons per hour in my scenario. That number is INCORRECT.
__________

Here is another source (a chart published by a marine hardware company) that I should have used to compare with the calculations up above:

Here is a chart that gives an idea of how small diameter holes in a boat can flood a boat quickly. http://www.cruisersforum.com/forums/...1&d=1352065660

Looking at that chart one finds:

A 2" hole 3' below the waterline will flood a boat at 139 Gallons Per Minute.

139gpm x 60min = 8,340 Gallons Per Hour

About 8,000GPH IS much more than 4,000GPH (what I posted in my OP or top post about this scenario).

The result is that you have even LESS time to respond in the scenario because twice as much water is coming into the boat in the same time, filling the boat much faster.

So, thanks again to BOATPOKER for catching that earlier error.

[Kelkara]

Originally Posted by Pete7

Also 4152 GPH sounds an awful lot of water, have a look at this, its not exactly pouring in even accepting US gallons are a bit on the short side compared to other countries gallons.

To quote from the video ... 2 (UK) tons (4480lbs) of water in 7-8 minutes ... doing the calculation ~= 4000GPH (US).

So even if the quoted figures are a bit approximate, what you see in the video is pretty much the kind of leak being talked about - and their hole was just 8" below waterline.

On my boat The batteries are high enough so they won't get flooded before the boat sinks, and even at half charge my pump should run for a few hours before the charge is all gone. But, as was pointed out above, there's no way the boat would still be afloat with 4000 gallons on board, and there's no way the pump could keep up with that flow ... so the pump will keep pumping until the boat has sunk. How much time does it buy? who knows, but hopefully enough time to check all the seacocks and put in a bung if one has failed - and if it's worse than that ... then hopefully there's still enough time to launch the dinghy and scream Mayday.

[Steadman Uhlich]

According to the chart I linked earlier, a 2" hole just ONE foot below water line will have a 80GPM flow.

But, I suspect most seacocks that are inaccessible or hard to reach and may have engine hoses (raw water intake) are 3 feet below waterline. Or more in larger boats.

The deeper and larger diameter holes make for much faster flow of water.

[a64pilot]

Originally Posted by Kelkara

To quote from the video ... 2 (UK) tons (4480lbs) of water in 7-8 minutes ... doing the calculation ~= 4000GPH (US).

So even if the quoted figures are a bit approximate, what you see in the video is pretty much the kind of leak being talked about - and their hole was just 8" below waterline.

On my boat The batteries are high enough so they won't get flooded before the boat sinks, and even at half charge my pump should run for a few hours before the charge is all gone. But, as was pointed out above, there's no way the boat would still be afloat with 4000 gallons on board, and there's no way the pump could keep up with that flow ... so the pump will keep pumping until the boat has sunk. How much time does it buy? who knows, but hopefully enough time to check all the seacocks and put in a bung if one has failed - and if it's worse than that ... then hopefully there's still enough time to launch the dinghy and scream Mayday.

I think without a "real" crash pump, that is about all the time we will have, maybe with a serious pump it will buy enough time to do something to at least slow the deluge, but I don't think we appreciate just how much water this is, forget a manual pump or bilge pumps with alligator clips, especially without a serious power supply.

Those of us that may have liners or furniture that blocks inspection of the entire hull, a fire ax or similar demolition tool might not be a bad thing to have.

[tkeithlu]

Thank you, Steady Hand. Plugging the hole and running the pump in even a losing situation are both ways of buying time, and I agree with both. What bothered me, and in part led to my building my own trawler, were the incredible number of through hulls I found in commercially built boats I could afford, and their locations (under engines?) that would prevent your stopping the leak in time even if you had the soft wood wedges tied to them. I met a Nordhaven owner who told me his 1980s boat had 27.......Fewer through hulls means longer hose runs, but my boat has two, one of which (sewage) is normally closed, and the other one (all uses of seawater) can be closed by pulling a wire in the main salon above the engine room. Usual bilge pumps, including mine, really are a marginal solution, and batteries are always low in the boat.

[Pelagic]

Hi Steadyhand,
I congratulate you on providing a good challenge for discussion.

Please ignore those who want to shoot the messenger.[emoji3]

I would just add to your 2" scenario that there is no one within VHF range and it is in rough conditions.

The only correct answer to a 2" hole in an already flooded bilge with that one pump, is that unless you can stop the ingress, you will probably sink!

The solution is simple and much cheaper than a life raft.

First you need to reduce the water level in the bilge to locate the break in the hull, assuming all thru hulls have been checked and closed.

For about $800 you can buy an emergency manual pump (Gusher 30).. that will remove about 31 gallons a minute

http://www.whalepumps.com/marine/pro...lyID=Gusher-30

For my size I have 2, portables mounted on plywood bases.

Each with a screened suction hose that will reach from the lowest bilge to the deck
(They also have a coupling on discharge to attach a fire hose)

Once location of ingress is located, if inaccessible, a short shaft fire axe, (another good investment) opens it up so you can plug from the inside and work on your other problems.

There have been other threads on engine mounted crash pumps, (which I have)
petrol scow pumps (I do not have)
plumb engine raw water pump to become a bilge pump..(risky)

But when Murphy hits and you need to locate a large hole...portability and large capacity will identify the area.

On the Electrics....your best investment with those is very good alarms for each low point.

[SailingFan]

Originally Posted by tkeithlu

Thank you, Steady Hand. Plugging the hole and running the pump in even a losing situation are both ways of buying time, and I agree with both. What bothered me, and in part led to my building my own trawler, were the incredible number of through hulls I found in commercially built boats I could afford, and their locations (under engines?) that would prevent your stopping the leak in time even if you had the soft wood wedges tied to them. I met a Nordhaven owner who told me his 1980s boat had 27.......Fewer through hulls means longer hose runs, but my boat has two, one of which (sewage) is normally closed, and the other one (all uses of seawater) can be closed by pulling a wire in the main salon above the engine room. Usual bilge pumps, including mine, really are a marginal solution, and batteries are always low in the boat.

I agree about the time issue, as I recently saw a boat in the yard that looked like the wall of the Al Capone suite perhaps a foot below painted static waterline. There were so many holes that when a PO had filled them, he/she must have used literally gallons of epoxy resin, and I would bet the hull changed deflection modulus characteristics due to the "dotted line" nature of all those hole fills. It was horrific, in the least, and I would never own such a vessel, let alone sail in it into water deeper than the transom height from cockpit decking.

This thread is an effective one in its intent (good job, despite initial resistance you encountered!), as the conversation here points out quite clearly that a single bilge pump and battery are not enough to assure much, and multiples would still only be purchasing time until the leak(s) are discovered, located, isolated, plugged, and finally, repaired. Solo sailors would have a very hard time at this on a glass boat below the waterline, but above the line, perhaps some epoxy or glass resin and a square of glass or even some cardboard (I once used a bank deposit envelope) can patch the hole and keep splashes of water out until cured, at which point the vessel can actually be heeled and used.

The hull will look like crap with a "Barnett Bank" envelope showing through blue tinted glass resin to any who cared to look from the outside but that is a minor inconvenience and can be easily appreciated by any who are on the inside of said hull. I kept a healthy supply of bank envelopes in those days because they were essentially free and they stored well in small spaces, while they also represented easy patch material because they did hold resin well. I had one on the side of my Toyota pickup as well, right where the rust line went through the side of the truck bed. The officer told me that if the 2 liter Mt. Dew bottle fell out, he was giving me a $250 US littering ticket fine, so out came the envelopes and resin... Hey, you have to be resourceful when you are less than wealthy enough to get new vehicles when the old ones are paid off, despite the rust...

[SailingFan]

Oh, and I still don't like the bosun's chair...

[snort]

It's a good topic and SteadyHand is a boating scholar, in my humble opinion, for his always thoughtful posts on varied subjects.
I have a hatch leak, and am amazed out how much water gets into the bilge just from rainfall overnight. It's literally gallons.
So, having a hull holed would be a whole other ballgame. Having the bilge alarm would be the most important thing because you'd want to get to that problem asap and stuff it with something to stop the water ingress.
At any rate, good post!

[Don C L]

Aha Steady, do I see you pondering your own future bilge pump designs???
I read a book once that said, "the best bilge pump is a scared man with a bucket." Personally I think that if you have a 2 inch hole and you can't find it and plug it, you are going to...eventually... wait for it... sink!

[Snore]

As you and others stated this is an unsolvable challenge.

There are some additional variables to ponder. How old is the pump? What is the condition of the pump? Does it have a screen? How often are you clearing/checking the screen to ensure it is not clogged. These variables will alter the ratio of watts used to gallons pumped.

Part of my "worst possible" plans (besides the whale pump) is bailing with a 5 gallon bucket from the salon to the cockpit and allowing the water to flow out the scuppers. When the scuppers stop draining, it's time to go.

All this only works if there is crew that can bail faster than the water is coming in, OR you stop the leak.

That said, if there is crew, getting the engine running is a high priority. This ensures the batteries are recharged. Additionally, if the choice is sink or risk engine damage- I would cut the raw water hose to the engine and jury rig the intake hose so the engine is another pump. Once the engine is on-line, the scenario changes for the better.

[moseriw]

Hmm I planned for this szenario. 4 x 225Ah Batteries in the middle AND one on top of the other! AND exactly this 4000gph rule pump (My BigBoy) AND two 450Gph service pumps with a head of 3 ft. should make the 4000gph for 10 hrs (Voltage drop fm 13,8V to 10,8V)

Hmm forget to say that my 2,8 m² Solar panels will charge with 8 to 16 Amps during the day too.

BigBoy has an 120 Db alarm on deck so if it happens in a marina with no one on board the whole marina will be awake ;-)