Bilge pump capacity

[Alisske]

I had gotten a new “to me” boat (26 downeast single screw diesel) about 10 years back. First order if things was to take care of the engine and emergency systems. Spent a lot of time figuring out bilge pump set ups and capacity as well as scuppers etc…. I take the boat on fairly long trips over open waters. .

One of the main things I wanted to understand was “when is a hole too big?” to be managed by pumps? I spent a good amount of money setting up two substantial pumps (2) 10 GPM electric utility puppy pumps and (1) 1.25 inch main motor driven Jabsco pump at 60 GPM. I chose not to have a “Y” set up for my raw water pump since the last thing I'm gonna be doing is messing with my motor during an emergency (some folks may disagree, but thats my belief)

For a boat my size and was able to shed about 80 gallons a minute.

The chart below is typical water flows for pipes and served as my reference for calculating how much water can enter a boat for a hole diameter size. Now i know water flow dynamics is a tricky beast (depending on depth in water, run and height of DC hoses, time a hole can spend out of the water in wave actions etc…).. BUT, the flow rates are astonishing. For my boat, I assume anything over a 1.5 inch hole and it is a matter of time before I sink (unless repaired).

Now before everyone starts talking about repairing, there may not be access, or you cannot locate the hole, etc….

I feel it’s important to know these things in advance because it will dictate the response to the emergency.

I just wanted to get other folks opinions. I see plenty of the trawlers have trash pumps set up (which i think is awesome).

 

[FF]

The hassle is most water pumps are very generously rated at zero lift.
Make the pump lift 3-6 ft and their numbers change a great deal.

Sometime after washing the bilge lash a bucket in place to measure actual output on battery power.

HOWEVER,

If you can find the leak,rubber gloves and some epoxy might be a big help.

TotalBoat
TotalBoat Underwater Repair Epoxy
Starting at $53.99

 

[psneeld]

Damage control is an encompassing concept that includes pumping capacity but not only pumping capacity. The ability to help reduce the inflo of water is usually pretty critical.

Most pumping setups are based on a hose coming loose/separated/etc. while boats are at the dock...maybe underway. Most of the time the capacity isn't realistically based on collision or progressive flooding situations.

For the average recreational boater and crew, it is realistic to think of collision and/or progressive flooding like fire. If the immediate response is not supccessful, abandoning ship procedures might be in order (certainly thought through ahead of time).

 

[Turtle Blues]

Second the progressive step plan.
Have 3 1500gph pumps mounted in the bilges.
The emergency bag has a 4kgph pump with alligator clamps on the wires and a 25' rolled up blue hose, a pair of the conical emergency plugs and a tub of the sealing compound.
Son was on a boat that lost a prop and shaft at cruising speed. By the time they got the deck hatch open he was diving in the bilge to assess the damage.

 

[Gdavid]

I suspect that most boaters do not have a very solid grasp on the critical risks and considerations when it comes to flooding control specific to their individual boats. There is only so much damage control one can do if you strike a sea container and cave in a massive area of your hull but on the other hand, would you be able to stop flooding around your prop shaft of your stuffing box seized to the shaft and ripped the hose off of the shaft log? How susceptible are your engine room vents to shipping water aboard?

Most boats sink unattended at the slip, I suspect that the majority manned sinking vessels is due to mechanical failure which could have been prevented through better maintenance, effective identification and flood control, and a better understanding of secondary flooding sources. I'm just guessing on all of this.

It is straightforward to install 4 bilge pumps and conclude that you have X gpm pumping capacity but it is far more complex but equally important to figure out at what level of water in the bilge, rate of rising water, and what degree of list (heeling) do you need to be planning your exit.

One good safety precaution would be ensuring that multiple members of the crew can operate the vessel in emergency conditions and communicate to rescue parties while the "ship's engineer" can be focused on damage repair. Unfortunately, in most cases the person most knowledgeable with the ships systems and potential flooding sources, is also the most qualified helmsperson and not free to focus on damage control. This is certainly an area I need to improve upon on my boat.

 

[psneeld]

The average boater might be amazed at how many sinking boats stop sinking the minute they throttle back, the engine(s) quit, the boat changes course, or the fresh water tank stops leaking.

 

[Gdavid]

The average boater might be amazed at how many sinking boats stop sinking the minute they throttle back, the engine(s) quit, the boat changes course, or the fresh water tank stops leaking.

I taught US Sailing affiliated courses for years at a popular school in Annapolis, sometimes we used boats borrowed from our sister company, a boating club with well used and generally well maintained boats. On one particular bareboat cruising course, I missed the memo that one of the two water tanks under the settees was out of service due to a broken inspection hatch, so I topped off all the tanks and we promptly drained about 1/4 of one of them back into the bilge as we started sailing upwind. It was no big deal as there were only two of us onboard and we make frequent harbor calls as a matter of practice but I've heard multiple accounts of frightened sailors rapidly bailing all of their potable water overboard in the middle of long passages before realizing the situation.

 

[rslifkin]

I plan based on the idea that the de-rated (as installed) capacity of pumps should keep up with a failure of the largest / deepest underwater fittings. That way you have time to find the issue and attempt to at least slow the flow before the water gets deep enough to either start disabling systems or prevent access to the hole.

On my boat, the worst cases would be a lost shaft, rudder, or engine intake thru hull, any of which could put 50 - 60 gallons / minute into the boat.

Of my current pumps, I figure the smaller, low water pumps in each of the 3 bilge areas will move 5 - 6 gallons / minute in the real world. There's also a big Rule 3700 in the engine room bilge (other bilges will flow into this one if their water level becomes excessive which should move about 40 gallons / minute as installed with hose losses, etc.

I'm planning to add a couple more pumps: one will be another small-ish (should move 6 - 7 gal/min as installed) pump as a mid-level in the engine room bilge (the 3700 is up pretty high as it's too wide to fit very far down into the keel sump). That one will be above the main small pump, but below the 3700 and also will trigger an audible alarm. I'm planning to also add a second (alarmed) pump in the aft bilge, as that has several potential water ingress points and would only flow into the engine room bilge once the water level gets high enough. The forward bilge drains to the engine room bilge and only has a single 3/4" thru hull in there, so unless I punch a hole in the hull up forward, a failure wouldn't exceed the water that can be moved by the forward pump and transferred through limber holes to the engine room bilge.

 

[GoneDiving]

My dinghy has a bilge pump outlet roughy the same size as it's drain plug and will pump water out faster than it enters if the plug is left out. Note this is only when the inlet is a couple of inches below the surface. It would be totally different if the "crack" was feet down.

I see pumps as providing time to affect an emergency repair rather than beating the incoming tide. For any damage larger than the outlet size of the pump(s) it's only a matter of time if it's not plugged.

 

[psneeld]

I wouldn't think outlet size is the best indicator...as pumps and depth of holes vary in flow not solely based on size but some pressure variable too.

 

[SoWhat]

Removed a hose from a seacock this winter, shut the valve, shipyard launched the boat, I went down a few ours later - water over the floorboards! Very exciting moment!!! After the initial surge of panic, I figured I should check all the seacocks.. The first one I checked was the one I where I had removed the hose. It was like I left the faucet on. I quickly tapped the handle and the flow stopped. Who knew 90 degrees wasn;t closed. (Yes, I have wooden plugs and no, I hadn't plugged the seacock. And the float switch is always off, I have old iron fuel tanks))

After action analysis: The majority of my bilge is inaccessible (I have diamond plate screwed down) and any hole in the side of the boat is inaccessible. The transducers are inaccessible. The 4 seacocks are accessible unless covered by 2 feet of water and I'm not sure I want to be trapped in the ER if there's 2 feet of water in the boat.

If I derate my 2 1500 gph pumps I would barely be able to keep up with a 1" hole 1 foot under water. A third through hole will be installed this winter.

Lessons learned: Check certification date on life raft.

 

[HTurner]

 

[danderer]

I wrote this a couple years ago about our previous boat -- it still represents my thinking:

I felt pretty comfortable with my current setup: 4 pumps with a total nominal capacity of 8500 GPH on a 40' boat.

However, when changing the depth transducer I realized a failure of even that single small fitting would overwhelm all my pumping capacity and sink the boat.

The math is pretty straightforward. Even assuming all 4 pumps work correctly my effective pump rate would probably be 4000-5000 GPH. The transducer fitting, a 2" hole located 2' below the waterline will admit about 6700 GPH.

Absent quickly acquiring more pumping capacity or stemming the flow, the boat is going to the bottom.

That is just an example, but my takeaway is the importance of the advice above: Be ready to deal with flooding situations by limiting the ingress of water--don't just expect to rely on your pumps.

 

[sbman]

Removed a hose from a seacock this winter, shut the valve, shipyard launched the boat, I went down a few ours later - water over the floorboards! Very exciting moment!!!

...

Lessons learned: Check certification date on life raft.

I think the lesson I'd pull from that is to not allow the boat to be launched without a knowledgeable captain on board to check the bilges, seacocks and other potential sources of water ingress immediately after launch.

 

[HopCar]

Bilge pumps aren’t meant to keep a boat afloat.
They are time machines. The more capacity you have the more time you have to solve the problem.

If you think about it, the smaller the boat the more pumping capacity you need. It takes a lot less water to sink a small boat than a big one.

All boats should have bilge pumps to buy time.
Signal equipment to call for help.
Repair supplies to make good use of that time.
An abandon ship plan and equipment to execute the plan.

 

[SoWhat]

I think the lesson I'd pull from that is to not allow the boat to be launched without a knowledgeable captain on board to check the bilges, seacocks and other potential sources of water ingress immediately after launch.

Shipyard does not allow owners on board when it is in the slings being launched. Shipyard may, may give you a day but not a time for launch. Shipyard does not check your boat after launch. They go get the next boat. They call you once it's in. I always go down at some point after launch but after years of no problems there was no sense of urgency.

Moral of the story is the handle isn't necessarily closed at 90 degrees on old bronze seacocks, and plug the seacocks if you remove a hose.

 

[psneeld]

I have been to quite a few yards launching boats and I have NEVER been to one that released a boat from the slings without the owner or agent or yard member aboard to check for flooding till the final release from the slings. You don't go aboard till the boat is just barely in the water...but they don't release the boat until it is checked for flooding or non-engine start or the tow vessel moving the boat says OK.


Not saying a yard won't do it...but in dozens of yards up and down the east coast...including one I did today...the yard waits till the owner/operator/yard guy say drop all the way for pull out.

 

[rslifkin]

The yard I'm at checks as well or sends the owner aboard to check. Normal procedure is to lower to just short of fully floating, check, then drop the last bit and walk the boat out of the slings. Tie up in the outer part of the pit and prep to start up and move (or set up for a tow) while they're getting ready to launch the next boat.

 

[PM]

A 1500 or 2500 gph pump, or any rated pump for that matter will not pump at its rated capacity. I don't know how they get away with these false ratings but they do. Think of a commercial milk truck or chemical truck or fish transplanting truck or a septic pumping truck or a pool filling truck. Do they have a 12 volt, ninety dollar pump to fill and empty it? Of course not. They will use an engine driven pump or a firehose type of pump.

Those numbers are fiction, based on some calculation which will not hold up in the real world.If you put a bilge pump to the task of emptying a 3,000 gallon tank of water one of two things would probably happen. You would lose your 12 volt power supply (dead battery) or your pump would fail after a couple hours (plastic non lubed bearings).

A garden hose with good pressure will fill a five gallon pail in about three minutes.(about 100 gph). Do you really think a $100 dollar bilge pump will pump thirty times that amount?

Don't believe everything the manufacturer claims.

pete

 

[OldDan1943]

Bilge pumps buy you time to determine the source of the egress and time to determine if the boat can be "saved" via damage control plugs and your additional bilge pump. Beyond that, the bilge pumps give you time to get to the life raft.
Let's not be fool hearted....
Pump size? What is the largest through hull, flooding rate? Add 10%. Bilge pump size, water determine the flooding rate, add 10+%. You might want to carry a 'mobile bilge pump' with alligator clips and a hose long enough discharge overboard or at least to the outer deck.
You just need to show/prove to your insurance company, you tried your best.
Trust me, you can over protect. And that is why you carry your like raft and if you are lucky, launching your RIB with an outboard and gas too. Dont forget the PFD and a couple of hand held VHFs and flares and or the currently popular 'blinking lights.'

 

[FF]

Bilge pumps usually have DC motors , which run fast at 14.4 engine on voltage, somewhat slower at 12.8 , fully charged, and lots slower at 12,0 almost dead.


Be sure to test pumps on battery power alone.

 

[psneeld]

From BoatUS.... not sure it's accuracy, but probably at least good guestimates and it show you that the manufacturers claims while wildly optimistic in practice can be approached if you understand why the reduction in capacity happens.... and how you can make sure the install isn't the majority of the problem.

 

[PM]

psneed, thanks, that diagram makes a lot of sense. People dont seem to understand that there is a TON of resistance in corrugated hose, a lot of friction and resistance to overcome. The longer the discharge hose the more resistance. The "lift" also needs to be considered.

pete

 

[Benthic2]

I've never been involved in a near sinking but I would think that the height of your batteries would play a major role in an emergency pumping situation. If you assume that you are not going to be aware of the flooding until a high water alarm goes off, or the handling of the boat feels "heavy".....and you only have until the battery posts gets submerged to get ahead of the problem....it may be that your notification time is as important as your pumping capacity. I have often thought an indicator light at the helm that showed bilge pump activation or better yet, run time would be very useful.

 

[psneeld]

I have helped salvage boats where the batteries were submerged for hours, maybe all night, and were still running the bige pump when we brought them to the surface.


I wasn't true of all boats, but the batteries were possible dead already and that's why the boat sunk. Hard to tell.



I wouldn't count on them working while submerged.... but there is a chance.... that you shouldn't bet on.

 

[SoWhat]

I have been to quite a few yards launching boats and I have NEVER been to one that released a boat from the slings without the owner or agent or yard member aboard to check for flooding till the final release from the slings. You don't go aboard till the boat is just barely in the water...but they don't release the boat until it is checked for flooding or non-engine start or the tow vessel moving the boat says OK.

Not saying a yard won't do it...but in dozens of yards up and down the east coast...including one I did today...the yard waits till the owner/operator/yard guy say drop all the way for pull out.

Clearly you have not hauled in Boston. They may have ten boats scheduled to launch in the morning, then 2 boats come in for an emergency haul. They simply have no time to check boats or wait for owners to show up. Once a boat is in the slings, the hydraulic trailer is off to get another boat. They are a safe and efficient operation.

The yard guy (the young kid) simply hooks up the tow boat and moves it to the slip. The owner is then notified by phone.

 

[rslifkin]

Clearly you have not hauled in Boston. They may have ten boats scheduled to launch in the morning, then 2 boats come in for an emergency haul. They simply have no time to check boats or wait for owners to show up. Once a boat is in the slings, the hydraulic trailer is off to get another boat. They are a safe and efficient operation.

The yard guy (the young kid) simply hooks up the tow boat and moves it to the slip. The owner is then notified by phone.

To me, that sounds like a yard that cares about nothing but money and getting more boats through, doesn't give a damn about the safety of the boats and can't be bothered to do things right. And knowing they work that way, I'd never go there outside of a dire emergency.

 

[psneeld]

Clearly you have not hauled in Boston. They may have ten boats scheduled to launch in the morning, then 2 boats come in for an emergency haul. They simply have no time to check boats or wait for owners to show up. Once a boat is in the slings, the hydraulic trailer is off to get another boat. They are a safe and efficient operation.

The yard guy (the young kid) simply hooks up the tow boat and moves it to the slip. The owner is then notified by phone.

The I am glad I am not in Boston...really just another reason...


Thankfully all the way from Jersey to Florida, the yards I have used or visited don't work that way and believe me, many are just as busy and still have a responsible person onboard to check...because the liability would be too great not to. Some day the yards you describe will lose their bet in court.


If launching a boat and not checking immediately for flooding is your definition of safe....


Most lift operators that that have launched me, specifically ask if everything checks out.

 

[Gdavid]

I was just launched Tuesday, busy yard that does not promise to launch on a certain day or time but they absolutely require access to all hatches and they check. I doubt they stare as long as I would but they have no interest in a boat sinking in their marina

 

[psneeld]

Absolutely Gdavid, a sinking boat would interrupt the launch schedule anyway.


I also have never had a marina refuse hoist a sinking boat if they can...because they can charge a fortune to interrupt their schedule. Just like increased rates during hurricane hauls.