Bilge pumps

[KEVMAR]

I have a 1983 36 albin .. how many bilge pumps should I have , where should it or they be located and what kind ?? Thanks

 

[jleonard]

I have a 1983 36 albin .. how many bilge pumps should I have , where should it or they be located and what kind ?? Thanks[/QUOTE

As few as you feel comfortable with.
That said I have 2 bilge pumps one a little higher than the other mounted in the center of the boat at pretty much the low point of the bilge.
My shower pump would activate if the level got over the edge the sump.
There is a manual pump also, but I have never tried it.

 

[DavidM]

For a 36' Albin I would recommend at least two. One should be a medium volume (500-1,000 gph) pump mounted in the low part of the bilge. The other should be a high volume (2,000+ gph) mounted a few inches higher, or at the same level with its float switch mounted higher. Make sure that you have adequate sized hose and thru hull to handle the high volume. This is an emergency "keep your boat from sinking" pump. It should also alarm at the helm.

If you have another bilge area that doesn't communicate with the main one, even if it always stays dry, I would put another medium flow pump there.

David

 

[diver dave]

If the boat pitches up a bit underway (what boat doesnt) make sure aft gets a pump. Use independent power sources too.

 

[CharlieJ]

I use a Whale Gulper m/n 320 displacement pump for nuisance water removal. I mount a large submersible pump; e.g., Rule 3700, above the nuisance water level so that the submersible pump's shaft seal is never submerged under normal circumstances.

The primary (nuisance water) pump takes care of the day to day bilge water removal and is rated at about 5 gpm. The submersible pumps actuating switch ( I use WaterWitch) is set to turn the pump on after the high bilge water alarm has sounded which will sound if the primary pump cannot handle the egress of water. Powered directly from the battery bank via appropriate OCPD.

The toggle switch at the operating station is ON-ON. No OFF position. Switch is up, automatic operation via the WaterWitch. Switch is down, WaterWitch is bypassed and the pump runs.

Ensure that you match the OCPD to the manufactures' recommendations.

 

[Xsbank]

Decide first if the bilge pumps are to save the boat or to delay sinking while you abandon ship. Then Google how much water will enter your boat with a 1" hole below the waterline. Then double that for pump capacity to remove the water. Then look at the losses you sustain if you have to pump the water uphill and double the capacity again. Now look at the rating of the pump and see how it drops on battery voltage only (12-ish) versus engine-running voltage (14-ish) and increase the capacity accordingly and consider how big your battery bank is and how many amps these pumps will pull.

Now you are in the ballpark.

 

[sdowney717]

I have 5 electric typical bilge pumps in various places, my hull has 2 watertight compartment areas. So two Rule 3700, two Rule 2000, one Rule 500, for a 37 foot boat.

If you have AC power, consider getting yourself a pool pump, continuous duty rated, can pump salt water, built in large strainer, self priming if the strainer basket is filled with water, water can simply sit in it. Very reliable, inexpensive, easy to find parts, can move lots of water, multiple potential uses depending on how creative you are with piping and valves.

I have one I took apart and made sure it was functioning well, an plan to use it as a washdown pump. It could conceivably work as an emergency raw water pump for the engine too. But rigging up stuff in an emergency is not something I can do just like that it takes planning ahead for me.

 

[Comodave]

Our surveyor recommended 150 GPH/foot so for a 36’ boat that would be 5400 GPH of pump capacity. Several things come into play with bilge pumps. First they should have excellent voltage so they can produce the rated GPH so make sure the wire is large enough to supply the current needed. Second the type of discharge hose is important. You want smooth bore hose not the corrugated hose that is cheaper. The corrugations cause friction to the water flow and you loose pumping capacity. Third is the discharge head height. The higher you pump water the slower it will pump but you do want the discharge well above the waterline.

 

[CharlieJ]

Hole size and depth of hole below waterline -> flooding rate

Here is a table that I produced some years ago. For any sizable hole, your pumps will only slow the flooding, hopefully long enough for you to find the breech and mitigate the flooding at the source.

Otherwise, ensure your life raft is in certification.

 

[OldDan1943]

I think more boat sink at the dock than underway.

 

[Xsbank]

Great table Charlie, that example is 8340 gallons per hour. Pumps are rated at 13.6 volts so on batteries, you have a 20% voltage drop, Pumps are rated at level so 3' head would cost about 30%. Corrugated hoses, check valves or curves, etc. cost another 20% so doubling the pump capacity means 16,680 gallons per hour required installation to deal with a 2" hole.

 

[OldDan1943]

Great table Charlie, that example is 8340 gallons per hour. Pumps are rated at 13.6 volts so on batteries, you have a 20% voltage drop, Pumps are rated at level so 3' head would cost about 30%. Corrugated hoses, check valves or curves, etc. cost another 20% so doubling the pump capacity means 16,680 gallons per hour required installation to deal with a 2" hole.

Check valves in a bilge pump outlet, that's a big no-no.

 

[Comodave]

I wire my bilge pumps to a 3% voltage drop. Takes big wire but really an inconsequential cost when we are talking boats.

 

[sdowney717]

If you can seal the hull into multiple compartments, then much more likely the boat can survive getting holed. Titanic would not have sunk except too many compartments were flooded.