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Multiple bilge pump question

am_dew

am_dew

Advanced Contributor
"My boat has a small leak and

"My boat has a small leak and normally I have not worried about it since I trailer the boat and the bilge pump I have installed has always worked well to pump out any water that has leaked in and found it's way to the bilge. However, this summer I will be leaving the boat in the water for a week during a vacation. I am a bit concerned that if the one bilge pump were to fail I might wake up to find my boat full of water. So, I have thought about adding a second bilge pump as a backup. The question I have is do I have to drill a second drain hole in my hull for the new bilge pump's drain hose, or can I somehow tap into the existing bilge pump's drain hose? If the latter, I presume I would need to install some sort of Y valve or similar, but how do I do so without fear of water coming back into the boat via the other bilge pump's drain hose?

I know the real answer is to find and repair the leak, but I have tried and not been successful and the boat has been this way for most of its 37 year life. I know, I know...
uhoh.gif


Thanks!"
 
"My boat which lives in a slip

"My boat which lives in a slip all season long has two bilge pumps. A small one in the absolute bottom of the bilge to take care of rain water (Even with the top on, rain water comes in the rod holders and forward bilge vents). There is a second very much larger pump installed a inch and a bit higher in the bilge for those "s--- happens" days. Both are on float switches and wired to different batteries.

Finding leaks... A friend of mine had a problem like this once. We drew an arcs around the engine using water soluable markers from the transom around the engine and back to the transom on the other side of the engine. The leaking water "broke" the line. We kept drawing arcs back until we found the source.

To directly answer your question... you would need to install check valves in both pump lines. Check valves can be troublesome.

Alternative solution: buy a new pump to replace the one you have. Failure of a good high quality pump in one week is very unlikely. Running the battery down is a bigger risk."
 
"All boats should have two bil

"All boats should have two bilge pumps with completely separate wiring and drain hoses. I know it is always difficult to think about intentionally drilling a hole in your boat to add a thru hull, but in this case it is necessary. Just be sure to be well above the water line and have the bilge hose go higher than the thru hull. This will prevent water from the outside splashing in.

As Robert pointed out, your smaller pump should be the one that turns on first with the float switch. This will limit the current draw and prolong your battery charge.

Also, IMHO I would spend some time finding and repairing the leak for some piece of mind.

Good luck!"
 
"Bob, I endorse what Robert an

"Bob, I endorse what Robert and Dwayne pointed out. My setup is identical to Robert's, and each pump does have its own independent discharge overboard. Also, even if both pumps are set in "automatic" (each has its own float switch), they can also be started manually.

Don't know your particular boat, but have you checked that the nuts in the 6 carriage bolts holding the transom shield in place are tight? If loose, water may find its way into the boat between the transom and the seal surrounding the shield. Just a though."
 
"This is an important topic fo

"This is an important topic for those who moor.... IMO!
Bob, each pump should have it's own discharge hose and thru hull fitting.
You will want to create a system that will be as failsafe as possible.
Should you ever need this system while you are away from the boat...., you want it to have all of the advantages that it can!!!!!

Bob, if this is the boat pictured in your avatar, then much of this will not apply.... it's mainly for larger boats... but what the heck!

Bilge Pumps and Float Switches:

Bilge pump float switches, so called "Auto-matic" float switch controls, and so on, are often misunderstood.

In simple terms.. Your main bilge pump.... the pump that is going to keep your boat from sinking while you are not there, is going to require a float switch that is powered from an "Un-Interruptible" 12 vdc power source!
Not thru some goofy ON-OFF-AUTO mode helm switch!
But a float switch that receives it's power from a source that can not be turned off.
A source that is Uninterruptible!

For this connection, either # 1 or # 2 terminal of the rear of your MBSS (main battery selector switch) is an excellent location. (fused, of course)
NOT the Common terminal!
Either of these (schematically) are a direct battery connection ...... (but without the Rat's Nest at the battery itself)
Since # 2 is usually our "House Bank" and a much larger bank, this seems to be a better choice!

Now your "float switch" can independantly turn on the pump when it senses high water.
It is not dependant on someone having left the helm switch ON or in "Auto Mode".
It is not dependant on someone having left the MBSS ON.
And it will not be disarmed by someone accidentally turning a switch OFF.
It is ready to go so long as you have battery power.

Make sure that the mounting elevation of your float switch is capable of allowing the pump to draw the water down enough to shut itself OFF.
A float too low may keep a pump running."
 
"There are some small (500

"There are some small (500 gph)pumps that have built in float switches. There are pros and cons to this. If you have an external float switch and its out in the open then you run the risk of junk in the bilge disabling it. If you have an external float switch it should be in a "cage". External floats have the advantage of being easily tested. Internal float switch pumps don't need cages... and depending on your philosophy more difficult to test.

I don't view it this way since I "test" my bilge pump almost every time I take the boat out... with a hose when I wash the deck down. No scuppers on my boat. My big pump does however have an external float switch in a cage.

Rick is correct... wire pump directly to battery at the battery with a fuse. Further my "wired to different batteries". My main batery is a start duty, battery #2 is a start/deep cycle battery. The primary (smaller) pump is wired to the #2 battery (I often leave the cover off on weekends and sometimes we get T'storms that dump a lot of water in a short time and I don't want to kill the battery with repeated cycling), the big pump is wired to the start battery, since presumably if that ever has to run I won't be worried about starting the engine as the engine in that situation will either be running already or dead."
 
"Robert, I find that I end up

"Robert, I find that I end up removing more of those integrated pump/float switch combinations due to failure for the exact same reason that you site re; the independent float switches. They become clogged up.
That and those "In-Line" or "Turbo" bilge blower motors!
thumbs_down.gif
Errrrh!
If you have this much debris in your bilge, I think you have a problem maintaining your boat!
I'd never recommend either of those products to anyone.... not worth it.
(sorry, that did sound rather gruff, didn't it?)

On the issue of the float switch power supply...... The reason that I suggest the rear of the MBSS is due to the avoidance of the typical Rat's Nest that we can end up with at our batteries.
Not good, and is also a source for further corrosion at this critical connection of cables only...... at least in my book!
Schematically, this connection is identical..... but no terminal corrosion/no rat's nest.

For any of us who don't like the idea of using their largest battery bank for this.... I'd much rather end up with a low or dead battery bank, than a boat full of water!
(again, forgive my stern, hard headed sounding position on this... but I see this allllllll too often.)


One more thing since we're talking emergency bilge pumps.....
The very same circuit that excites the pump, is the supply-side "connecting" circuit of the float switch.
This circuit (on most of our boats) is common with the circuit that comes from the manual operation helm switch.
This (usually a brown wire) is a perfect place to connect an alarm or a buzzer.
Some will place a note on their moored boat with a message asking that anyone hearing this alarm cycle, to give a call to either YOU or the Marina.
Point being..... if you get a phone call, you will most likely have time to get to the boat and investigate before a dead battery and a non-working pump occurs.
If you have an O/B charger, this is usually a non-issue.

Again, just my take on this.
There are many ways to skin the same cat! So they say!

."
 
"Gentleman, thanks for all of

"Gentleman, thanks for all of your replies. I'm just curous how many boats the size of mine (16' runabout as seen in my avatar) have two batteries and two bilge pumps/outlets? I'm not questioning the need for the redundacny in any way as I fully understand what is at risk, but just curious how many pleasure boats like mine really do have this redundancy?"
 
"Bob, The answer is; [b]hardly

"Bob, The answer is; hardly any!

That is why I said: "Bob, if this is the boat pictured in your avatar, then much of this will not apply.... it's mainly for larger boats..."
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"
 
"Rick, thanks for that clarifi

"Rick, thanks for that clarification. I think at minimum I will put some more effort into finding and stopping the leak and that way even if the single battery/external float switch/bilge pump system fails for some reason, I can rest easy knowing the boat won't get flooded. And if I can't find the leak and in the unlikely event that my bilge pump system fails, I'll just be more than thankful that my family and I got to enjoy the boat for as long as we did, which is 37+ years so far."
 
"Well, back when I had an 18 f

"Well, back when I had an 18 ft I/O I had two batteries and two pumps. Then again I boat on Barnegat Bay in NJ and used to run outside thru Barnegat Inlet and fished in the Ocean (on "nice" days). The again one of those "nice days" turned into 4 to 6 ft seas with breaking tops when almost dead calm turned to winds from the SE. I was also out during small craft warnings on more than one occasion when our YC had bad weather blow in during a regatta.

It all depends on where you use your boat and under what conditions. "
 
I boat only either in relative

I boat only either in relatively small sloughs in the Sacramento River Delta or freshwater lakes. The boat is trailered in between outings except for the occaisional one week long vacation where I leave the boat in the water.
 
"El P had suggested earlier in

"El P had suggested earlier in this thread checking to make sure that the 6 transom shield bolts were tight as that might be causing the small water leak I have. This past weekend I checked them...the top 4 were not as tight as I think they should be, so I tightened them up snug. The bottom right was tight. The bottom left one I could see and barely get a wrench on but I did not have any room to turn the wrench due to it's close proximity to the exhaust elbow, and I did not have a large enough socket for it. Will have to buy a socket and try that."
 
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