Adding Electric Bilge Pump

[zinahewitt]

Hi All,

Hope your week is going well.
I have an old Dufour 34 from 1975. It came with a Manual Bilge Pump which I replaced.
The Bilge pump runs from the bilge and is connected to the scupper which is at the Cockpit.
I think the reason was that in case the bilge is filthy it will not mar the outside of the boat.


I was thinking of adding two electric bilge pumps.
A small 360 and a large.
The small I don't care how many GPH it will push as it is just a clean up one that will sit lower.

The big pump is where I am not sure how big I need to go.
If you look at the diagram, I estimate I need to run the hose 6 feet up, 3 down, so that is 20%-30% loss X2.

If I decide to go to the Chart table, then I assume if the bilge is dirty it will mar the boat.
I also am worried in case the boat is heeling extensively due to weather then water can come in.

If I decide to go to the scupper like the manual pump, then I was told it is not coast guard compliant as they consider it like the cockpit and you can't send bilge to the cockpit to be drained.

If I decide to go all the way back to the stern, I have a pretty long run so would lose in friction the 30% there, also same mar the boat issue, but I estimate this would be the safest.

So 4000, 2000, 1500 or just skip the whole thing if the boat has sailed for 50 years without sinking then Manual is fine.
If you can explain your work, I'll be most grateful.


Thank you

Saar

 

[Don S/V ILLusion]

id like to see “your work” when it comes to the numbers you lose in volume flow rate. It’s all about the head, not the distance.As to the size, bigger is always better (in this case).

 

[garymalmgren]

Hi Zina.
RE: The big pump is where I am not sure how big I need to go.

Correct me if I am wrong , but you seem to be under the impression that a large bilge pump is to stop the boat from sinking if it is holed .
The pump will give you some time to make a repair, However no pump can stop the ingress of water if it can't be stopped.
The pump will rum until it is blocked with debris or the battery goes flat. This is true with larger vessels too.

I am sure that there will be disagreement on my opinion, but here goes.

On a small sailboat the pump is for cleaning out a small amount of bilge water that has entered somehow.

The questions are
how often do you use the hand pump?
does it do the job?
will an electric pump do the job better (faster)?
are you interested in an easy DIY job that doesn't cost a lot?

gary

 

[dlochner]

@garymalmgren is correct, if the boat is sinking due to a hole or failed seacock, no bilge pump will be able to keep up with the flooding.

Read the specs carefully for the pumps, you will see that most of them are rated with 0 head at a voltage higher than 12.5 v. So the numbers are useful for comparing the relative size of the pump but pretty worthless for estimating actual flow.

Most bilge pumps are vane pumps and will not pump a bilge dry. Once the water level falls below the top of the vane the pump is no longer effective and any water in the discharge hose will flow back to the bilge causing the pump to cycle.

In addition to the amount of head the interior bore of the hose is important. Many cheap bilge pump hoses are corrugated. This introduces turbulence in the water flow slowing down the water. Bilge pump hoses should be smooth bore.

Out the transom is the best place for the discharge with a high loop to block any sea water intrusion.

 

[Captain Larry-DH]

If I decide to go to the Chart table, then I assume if the bilge is dirty it will mar the boat.
I also am worried in case the boat is heeling extensively due to weather then water can come in.

If I decide to go to the scupper like the manual pump, then I was told it is not coast guard compliant as they consider it like the cockpit and you can't send bilge to the cockpit to be drained.

If I decide to go all the way back to the stern, I have a pretty long run so would lose in friction the 30% there, also same mar the boat issue, but I estimate this would be the safest.

Chart table - yes you might get streaks if the bilge water is dirty. You can stop ingress when heeling if you use a check valve at the pump end of the hose. If the check valve fails it can introduce siphoning when heeled and that could be a big or little problem depending on how long it’s heeled. (Adding a check valve stops the back flow and reduces pump cycling, and will also leave standing water in the hose. It’s another maintenance item and when winterizing you will need to either open the hose connection to it or add antifreeze to the bilge so that hose is either empty Or filled with antifreeze.)
“T” it to the scupper drain - This is a bad idea because it lowers the effective drain point and can more easily allow siphoning than the chart table option. Also, marine growth or ice could block the drain and allow cockpit water to back flow into the bilge. I would not do this.
Stern is the best option - friction is not the issue, but increased “head” (height to pump the water) will reduce flow. It’s the safest and the only one I would consider if it was my boat. That long run will hold more water in the hose which will back-flow every time the pump cycles, and I would add a check valve to stop that back flow and reduce pump cycling, despite its minor drawbacks.
Edit - A 1200 GPH pump and 3/4” hose is workable for most boats - but you need to decide whether you have the space. I’d get the largest that will fit. None of the popular bilge pumps will pump fully dry, so use a shop vac if you want to clean and dry it well.

 

[Davidasailor26]

I would probably run the output to someplace on the stern quarter, maybe a little higher than where I drew the circle here. That way you can mount the outlet as high as you’d like without much streaking on the hull.

Use smooth walled hose to minimize the friction loss over the run. With appropriate sized wiring you should be able to keep the voltage drop to 3% or less; better than the 20% in the picture you posted.

Captain Larry gave a good description of the pros and cons of check valves for that type of run. A similar option is to use a remote diaphragm based pump with integrated check valves. That’s what Beneteau uses on many of their boats (with a course strainer on the intake hose) and it works fine for any nuisance water.

 

[dLj]

I was thinking of adding two electric bilge pumps.
A small 360 and a large.
The small I don't care how many GPH it will push as it is just a clean up one that will sit lower.

So 4000, 2000, 1500 or just skip the whole thing if the boat has sailed for 50 years without sinking then Manual is fine.
If you can explain your work, I'll be most grateful.

I'm not sure why you want to add two electric bilge pumps. You will have to look very carefully at that pump as to where it needs to be located and how it is run. I think it's a lot of bother for little benefit. How clean does your bilge get with the current manual pump? I'd just stay with that. But I don't know what your bilge looks like on your boat.

Adding in an automatic bilge pump is a very good idea - 50 years of good luck....

I personally would go with the largest size that fits easily. I've owned boats in the past that only had manual pumps. Getting an automatic bilge pump is a very nice upgrade!

I would run it out the transom. Others have commented more details I don't need to repeat...

dj

 

[jssailem]

My first step is understanding what you are trying to accomplish.

You have a scupper with an attached bilge pump. Modifying that would be the first item on my list.

Scuppers are intended to empty the cockpit of water. Sources of the cockpit water are either rainfall or breaking waves that wash aboard and fill the cockpit. It is known as getting pooped. The connection to the bilge suggests that water filling the cockpit could go to the bilge rather than overboard.

Electrical pumps are only good if you have electricity. If the water is over the cabin's floorboards, is your battery bank out of the water? If not, the size of the pump is irrelevant.

On the TransPac race, boats must have manual pumps, not electric ones.

On my boat, the scuppers and the bilge pumps empty out the stern. Dirty water is usually minimal and washes away off the boat. A two-step process addresses an oily bilge: first, identify the cause of the oil and solve it. Then, use absorbent "pigs" and mats to remove the oil from the water. Toss the oil-filled pig, and you can pump the remaining bilge water overboard.

 

[Dalliance]

The manual pump to the cockpit scupper is your emergency pump. Are you saying it’s connected to the same discharge through hull as your cockpit scuppers?

Add the two electric pumps on float switches as your nuisance water pumps, the primary lower in the bilge and secondary higher. Locate the discharge through hulls up near the toe rail where they will never be submerged, keep the hose runs as short as possible and use smooth walled hose. If you really want the discharges to be low on the hull, you still need to run the hose up high with an anti-siphon loop and back down. It’s not worth the added risk in my opinion.

Wire the two pumps directly to separate batteries. If the primary pump drains its battery while you‘re away, the secondary pump will still have power and buys you some time. The secondary bilge pump will not save the boat if it’s holed though.

Automatic bilge pumps can mask a minor problem until it becomes more serious. I recommend putting the primary pump on a cycle counter. This has provided me an early alert to issues several times.

Equip the secondary pump with a loud alarm. I have mine this way in the hope that if I’m away my dock neighbors might hear the alarm, notice water discharging where it doesn’t normally, and alert me or the harbor master. Of course the point may be moot if you’re on a mooring. In 16 years, the only time that secondary pump has activated is when I test it. Is the secondary really necessary? Hopefully not, but it provides some added piece of mind.

As for concern about dirty streaks on the hull below the discharge, I’ve seen stick-on drip guards on the West Marine website that might help. The product is stamped dripperguard.com. A clean bilge is the better solution though.

 

[zinahewitt]

Hi Zina.
RE: The big pump is where I am not sure how big I need to go.

Correct me if I am wrong , but you seem to be under the impression that a large bilge pump is to stop the boat from sinking if it is holed .
The pump will give you some time to make a repair, However no pump can stop the ingress of water if it can't be stopped.
The pump will rum until it is blocked with debris or the battery goes flat. This is true with larger vessels too.

I am sure that there will be disagreement on my opinion, but here goes.

On a small sailboat the pump is for cleaning out a small amount of bilge water that has entered somehow.

The questions are
how often do you use the hand pump?
does it do the job?
will an electric pump do the job better (faster)?
are you interested in an easy DIY job that doesn't cost a lot?

gary

Hi Gary,

Hope your week is going well.
I have used the hand pump twice, it was the original, it broke, I replaced it with a new one.
The hand pump is well located so easy to steer and pump at the same time.

I assume I put the electric in so that in case my boat is taking water at the dock, it does not flood
and in case I have a hole from an avid racer, it keeps me afloat while I rig something or get my liferaft ready.

I don't mind the cost, fixing the boat is my hobby along with sailing.

 

[FastOlson]

One missing piece of the puzzle seems to spec-ing out a Reliable electric pump, Centrifugal pumps are problematical for larger boats. As has been pointed out, they move a lot less water that the hyped-up numbers on the box, and are subject to air-locking.
Since for the real purpose of moving out "nuisance water" and buying time while you plug the unexpected leak, you ought to consider going with a reliable pump. I would recommend a Jabsco. like the 37202- series. Our boat came with two of these with separate discharges, plus a "category one" Whale manual (big!...) pump adjacent to our helm position.

Jabsco Shower & Bilge Pump - 2.8 Gpm - 12v

Jabsco 37202 Shower and Bilge Pump37202 Shower and Bilge PumpFlow Rate Nominal 13 Litresmin 3 USgallonsminSelfpriming from dry up to 2m 6ftFeaturesQuiet running and fully corrosion resistantCosntructed from corrosion resistant materialsSuppl...

www.hodgesmarine.com

 

[jssailem]

Here is a picture of the stern and the various scupper/bilge and exhaust pipes. The bilge is the smaller diameter through hull, on the left of the exhaust. The exhaust has a black flapper that serves to stop a following wave from pushing water up the exhaust system.

 

[thinwater]

You need to find the performance curve for the pump you have in mind. This is for the Rule 1100.

total head = static head + friction head + velocity head

Look up the friction factor for the hose you have in mind (correlated hose is terrible--very rough). Looks like about 1-foot of head for every 10 feet of hose, but it is more if the hose bends, so figure ~ 1.5 feet for 10 feet. You have a 3 foot net rise, so 4.55 feet of loss. Then there is the velocity head (how high the water would squirt int the air), which is about 1 feet, so....

TDH = 3 + 1.5 + 1.5 = 6 feet discharge head.

The pump will theoretically be at about 500 gph, but figure about 350-400 gph after some wear and gook in the hose (don't leave this out!). So in fact, you will only get 32% of the pump rating (not the 20-30% reduction you hoped for). Yes, this is kind of a cheat by the pump makers.

BTW, this is a trial-and-error calculation. Guess a pump flow rate, figure friction, plot the actual flow, and repeat.

This is how engineers calculate pump output.

L

 

[garymalmgren]

This is how I would mount an automatic electric bilge pump in a Dufour.
Short run to either port or starboard. Riser loop and exit 4 inches above water line.

 

[zinahewitt]

This is how I would mount an automatic electric bilge pump in a Dufour.
Short run to either port or starboard. Riser loop and exit 4 inches above water line.
View attachment 228592

Thanks

 

[jrussnogle]

This is likely the most important chart to look at. I’d spend more time thinking about methods to use to stop a major leak/hole rather than bilge pumps.

 

[thinwater]

This is likely the most important chart to look at. I’d spend more time thinking about methods to use to stop a major leak/hole rather than bilge pumps.

^^ He's not wrong, but this isn't either/or.

a. Leaks are most commonly cracks or loose fittings much smaller than those on the table, but very, very difficult to work on if you can't control the flooding.

b. After you control the leak it will still likely be pissing a significant amount, and there is still the initial amount to dewater.

During a delivery on a cruising cat I learned that the sounder was removed during the inspection and not replaced properly. About 15 hours in the o-ring blew and flooded the compartment elbow deep with ice water. The boat had only a manual bilge pump, so clearing the water while I fixed it was a major pita. A 500 (true) gph bilge pump would have been so nice. Just sayin'.