Whats your bilge pumping capability?

[soggy_feet]

I found a deal on a couple 360ish gph pumps last winter, and bought them with plans of building some partial bulkheads and compartmentalizing my steel hulled boat so the entire thing doesnt have to get wet if I have a few good ones come over the bow. I was just running the numbers in my head, and I THINK Im getting close to what I think proper water pumping should be for the size craft I have, which is a 15,000lb, 40ft houseboat.

In an OH S**T situation, if every compartment (will be set up for 3) were to have water in it, I could move 2610GPH. I plan on increasing that number by 1000-1500 in the next 2 years. I have smaller pumps thruout the boat, but back with the engine I have a small float activated pump, and a 1000gph pump on a switch, a few inches higher with the thinking that if theres one area above all that I don't want totally flooded with water, it would be the area with the propulsion unit, because as long as that stays running, I can at least power the thing onto a beach or something so I don't have to go diving to retrieve my belongings.

Its a bit bigger boat than most people have, but Im curious where people are at with this, so...

How big's your boat, and whats your max water pumping capability?

 

[DJ]

Re: Whats your bilge pumping capability?

I find bilge pumps of less than 1000 GPH pretty useless, except for the smallest of boats.

Another thing you have to consider is lift and what type of hose you use.

Having to to lift water more than a foot or two diminishes pump efficiency.

Also, a corrugated hose diminishes pump efficiency temendously. Always use smooth (internal) hoses.

I don't even have a bilge pump in my Boston Whaler. One, it's unsinkable, two, I never leave it outside.

 

[Art Bernard]

Re: Whats your bilge pumping capability?

2000gph here on my new/used deck boat. On my old fishing boat that I went offshore with (20' center console), I had 2- 2000ghp pumps just in case.

Art

 

[soggy_feet]

Re: Whats your bilge pumping capability?

I'm fortunate that I don't draft more than 16", so rise isn't too much of a concern, but I must confess that I use the cheap corrugated stuff... oops!

Its a low deck too, which means that when Im out in the middle of the lake, and the wind picks up, and I'm trying to get to sheltered water with 5-6ft waves hitting me, they tend to wash over the deck easily.

Worth mentioning its not a bad idea to check your pumps more often than not. I had a tiny splinter of wood block the impeller of my engine compartment bilge pump one year, while fighting to get back to the marina with 4 footers at my back. They kept washing into the fresh air cowls on deck, and when I got back, I found probably 50 gallons of water back there. Hardly touched the small pump and the wood dislodged and it started pumping, and then I kicked the big one on for full effect and had it emptied in short order. Could have been worse...

 

[Art Bernard]

Re: Whats your bilge pumping capability?

Yeah, I agree bildge pump tests are a good thing. Here in florida the "mud dobbers" love to build their nests inside the bildge pump discharge outlet. One of my pre season things I do is to jack the trailer up high as it will go and fill the bildge with water than op-test the pump. Every few weeks I'll stick the water hose to the discharge to flush out any mud dobbers.

Art

 

[roscoe]

Re: Whats your bilge pumping capability?

Lets see, 2.5 gallon bucket, so I guess about 1 gallon per scoop.

 

[DJ]

Re: Whats your bilge pumping capability?

I'm fortunate that I don't draft more than 16", so rise isn't too much of a concern, but I must confess that I use the cheap corrugated stuff... oops!

Its a low deck too, which means that when Im out in the middle of the lake, and the wind picks up, and I'm trying to get to sheltered water with 5-6ft waves hitting me, they tend to wash over the deck easily.

Worth mentioning its not a bad idea to check your pumps more often than not. I had a tiny splinter of wood block the impeller of my engine compartment bilge pump one year, while fighting to get back to the marina with 4 footers at my back. They kept washing into the fresh air cowls on deck, and when I got back, I found probably 50 gallons of water back there. Hardly touched the small pump and the wood dislodged and it started pumping, and then I kicked the big one on for full effect and had it emptied in short order. Could have been worse...

I have, in the past, wrapped bilge pumps with plastic window screen. It keeps the junk out of them.

 

[soggy_feet]

Re: Whats your bilge pumping capability?

I could've put money on someone saying something along those lines Roscoe!

I've found, in those situations, its good to trade off the bailing with someone every few minutes. The guy not bailing needs to do his best to drink as many beers as he can, as the empties are much lighter than the full ones. Don't want all that dead weight...


DJ, I've considered wrapping them in stainless steel screen from McMaster Carr... just haven't got that far yet. Its an old boat, with a loong to-do list.

 

[scoutabout]

Re: Whats your bilge pumping capability?

DJ hit upon a crucial issue - that of pump lift. All the numbers splashed across the packaging about gph are misleading marketing garbage that could get you sunk. Those numbers reflect a test with zero lift - i.e. no outlet hose but rather just running the pump in a bucket. Pump capacity drops dramatically once you consider how high the water has to be pushed to reach the thru hull fitting and overboard.

From BoatReports.com...

"...the question of ?lift? is important. Manufacturers rate their pumps for zero lift. It?s called ?open flow? or ?open bucket.? It just means that the water intake, discharge and pump are in a horizontal line. They often include the ?open flow? rating in the pump?s name.
The ratings serve only for comparison. When lift is introduced, few pumps will produce their ?open flow? ratings."

I've read that efficiency losses through lift or sometimes referred to as head pressure, coupled with voltage losses can mean real world performance is significantly less. Another review I read put a well known 3700 gph unit through its paces and couldn't get any more than 2400 gph out of it.

(Hopefully the mods won't consider this bashing - it's a critical safety issue that I'm sure many people aren't even aware of. It's my contention that, as a result of manufacturers inflating pump capacity numbers to look good, there may be folks out there blissfully unaware that their careful calculations to keep them afloat are critically flawed...)

 

[levi_tsk]

Re: Whats your bilge pumping capability?

as a partime plumber and fulltime pipefitter id like to think i know a little about head pressure so ill throw a little math at you guys :

a 90 degree bend is good for 3% in loss of efficiency of any pump
head pressure is defined as psig
and 1foot in rise is equal to .433 psig so for every 2.31'youll go up one psig and on a bilge pump youll loose about 50% of your efficiency
so for a 1000gph pump youve just dropped to 500 gph going up only 2.31 feet...
and for every 2.31' beyond that youll half that again and so onand id be willing to bet that a 100 gph pump wont overcome more than 6' or so of head pressure and thats with no bends just a straight pipe out of the outlet

 

[Beefer]

Re: Whats your bilge pumping capability?

I think you're under pumped. I have a 22', and I have 2 pumps; 1500 and 1100 - 2600gph (less rise). In a 40', I'd want at least 4000gph.

 

[soggy_feet]

Re: Whats your bilge pumping capability?

Thats exactly why I said I wanted to increase my capability by 1000-1500, sounds like I did my math correctly if you're coming up with the same numbers.

At first glance, even 3000GPH sounds like a lot, but as everyone has mentioned, once you figure in losses, and if you were to calculate what size hole that means you can put in the hull before it overtakes the pumps.... it really isn't all that much.

 

[smokeonthewater]

Re: Whats your bilge pumping capability?

a LOT depends on conditions.... If you are pumping out rain water then you might not need much at all.... If you rip a gash in your hull then 20,000 gph might only buy you a minute or two.... I have two 1500 gph pumps in my 28'er for emergencies which I hope to never need and a 375 that is probably all I'll ever need to handle any rain water that gets through the hatches faster than the channels can drain it overboard.

 

[dingbat]

Re: Whats your bilge pumping capability?

a LOT depends on conditions.... If you are pumping out rain water then you might not need much at all.... If you rip a gash in your hull then 20,000 gph might only buy you a minute or two.... I have two 1500 gph pumps in my 28'er for emergencies which I hope to never need and a 375 that is probably all I'll ever need to handle any rain water that gets through the hatches faster than the channels can drain it overboard.

I agree. You're fooling yourself if you think a bilge pumps is going to do more than buy you a couple of extra minutes. A good life preserver would serve you better

 

[soggy_feet]

Re: Whats your bilge pumping capability?

I agree. You're fooling yourself if you think a bilge pumps is going to do more than buy you a couple of extra minutes. A good life preserver would serve you better

Correct me if I'm wrong, but it sounds like you're saying its not worth it to bother with a big pumps?

A few years back my grandfather hit an unmarked hazard out in the middle of a big lake in the Adirondacks (wanna say Peck Lake). Up until a few years before, it was marked, but apparently whoever was in charge of putting that buoy out in the spring convinced someone higher up that it was too much work and not worth it. He put a 3 foot slit in the bottom of his 14ft aluminum boat, but stayed on the rock. Freaked out my grandmother (who can't swim).

He waited there until he could flag someone down. Not a lot else to do in that situation.

In another situation, perhaps closer to shore, and maybe not getting hung up, that 'few extra minutes' would be a lot nicer than watching your boat disappear under you while you try to race for shore...

In short, I still think its cheap insurance and better than nothing.

 

[smokeonthewater]

Re: Whats your bilge pumping capability?

big pumps are great BUT over thinking it and trying to figure out the magic number that will save your butt is a fools errand.... Just get the biggest pump you can afford and save up for another one...... ALSO the 14' boat is a TOTALLY different situation.... it only drafts a few inches.... these bigger boats draft a few feet.... the difference in the static pressure is AMAZING
A 3/4" hole could possibly sink a 40' boat in minutes... you might get 3000 gph through it depending on how far below the surface it was.... now imagine a 6" hole.... that might take it down in seconds

I can say from experience... that a 1250 gph rule won't keep up with a 3/4" drain plug in the bottom of a 5500 lb 26' cruiser..... I just forgot I had pulled the plug.... I launched the boat and parked the truck.... probably in the water for 5-8 minutes.... I got in the boat and headed about 1/4 mile out and shut it down.... I then heard the bilge pump running (had been the whole time) and popped the engine hatch to see over a foot of water in the bilge and a geyser of water shooting another foot above it.... put the plug in and all was good but I will never forget the speed that the water came in that little hole

 

[soggy_feet]

Re: Whats your bilge pumping capability?

Yeah, that advice sounds more in line to my thinking.

Beauty of my 40ft boat.... it drafts about 16". And its a steel hull, its not light.

Getting slightly off track, I went all last season with a 1" crack up on the bow. Boat was always wet, took forever to pinpoint the problem. WHen I did, I took a strong refrigerator magnet, gobbed some RTV silicone on it, and stuck it to the crack from the inside.

Wasn't paying to haul her out just for that crack, so the magnet trick was awesome. I lived on the lake until the end of October, then dealt with the problem.