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Old 07-08-2021, 08:34 AM   #1
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Y together two bilge pumps?

Our boat has two bilge pumps, both with their own above-the-waterline thruhull. However, the factory didn't really put the pumps in the three places where the water sits when the boat is at rest. Basically, slightly forward of the pump and slightly aft of the same pump. Sooooooo... I want to move the current one more forward and add another one more aft under the master berth (using one of those small Whale pumps with the remote pickup). This is primarily to remove the water that never leaves the boat (rain water that gets in the hatch) because I do have plans to add yet another Haus Daddy pump for emergencies in the near future. Anyway, for the forward pump, would it be okay to "Y" the two outputs together for the time being? Running a new hose for the new pump is going to be a HUGE PITA and I would like to tie that job to another future project rather that having to go thru the entire ordeal twice. I get that it will probably hurt the total capacity and that a check valve or two might be needed, but am I missing anything here?


EDIT* The other option, I suppose, is to use a very small bilge pump and pump it into the shower sump and let the sump take it overboard.
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Old 07-08-2021, 08:53 AM   #2
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Removing the final bits of water with bilge pumps to me is not the way to go.

For my whole recreational and pro career...I never really gave the dri-bilge concept a second thought.

Once I saw the DIY projects here and on YouTube, I had everything on hand except the $30 pump. So I tried one out.

Never been happier and never had a dry bilge like now.

The beauty of the setups is they can be rigged for multiple pickup stations and not the complexity or expense of the larger bilge pump setups that will still never get all the water out.

Sure adding bilge pumps with check valves can be done but I would never T in with check valves. Either connect them past the loop that drains overboard or make one tiny and pump it into a sump like a shower sump that pumps overboard.
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Old 07-08-2021, 08:54 AM   #3
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Do NOT put a Y in your bilge pump overboards. Dont consider a check valve in your overboards.
One bilge pump, one overboard. Two bilge pumps, two overboards.
End of story.
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Old 07-08-2021, 09:06 AM   #4
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I agree with OldDan. The running bilge pump will send water back through the other one when it is off unless you install check valves and check valves in bilge hose are fundamentally unreliable.

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Old 07-08-2021, 09:21 AM   #5
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i agree with olddan. The running bilge pump will send water back through the other one when it is off unless you install check valves and check valves in bilge hose are fundamentally unreliable.

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Old 07-08-2021, 09:22 AM   #6
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If it is just mopping up a little bit of water, maybe something like a Dry Bilge system. Run itís output to the shower sump. I bought one for the last boat but sold the boat before I got it installed.
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Old 07-08-2021, 11:20 AM   #7
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Thanks everyone
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Old 07-08-2021, 12:07 PM   #8
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Perhaps we/me should have started out with, "Why is isn't your bilges dry now?"
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Old 07-08-2021, 12:25 PM   #9
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I've only recently been made aware of the "dry bilge" concept. It apparently isn't a thing in the wooden boat community. I suppose it would be possible with a fiberglass boat, but I'm still unsure of the intended benefit.

Right now, I have water sitting in the toilet bowl at the house. Been that way for years. It isn't an issue unless, of course, there's something in there besides just the water. Why is water sitting in the bilge an issue? It isn't gray/black water, right?
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Old 07-08-2021, 12:29 PM   #10
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I've only recently been made aware of the "dry bilge" concept. It apparently isn't a thing in the wooden boat community. I suppose it would be possible with a fiberglass boat, but I'm still unsure of the intended benefit.

Right now, I have water sitting in the toilet bowl at the house. Been that way for years. It isn't an issue unless, of course, there's something in there besides just the water. Why is water sitting in the bilge an issue? It isn't gray/black water, right?
It promotes " boat funk" smell
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Old 07-08-2021, 01:43 PM   #11
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Once I saw the DIY projects here and on YouTube, I had everything on hand except the $30 pump. So I tried one out.

Never been happier and never had a dry bilge like now.

I am going to give this a go. Seems cheap and easy.
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Old 07-08-2021, 02:06 PM   #12
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I'm assuming the USCG not allowing bilge pumps to share an overboard discharge on inspected vessels has some reason?
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Old 07-08-2021, 02:11 PM   #13
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Not sure the USCG regulates anything about or even requires bilge pumps. 33CFR183
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Old 07-08-2021, 02:13 PM   #14
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Originally Posted by psneeld View Post
Not sure the USCG regulates anything about or even requires bilge pumps. 33CFR183
I assume he is talking about inspected vessels
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Old 07-08-2021, 02:22 PM   #15
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I assume he is talking about inspected vessels
Sorry, now rereading his post I see where he might be headed.

Yes Fish....sharing bilge pump outlets are probably a bad idea and the USCG most likely disallows them on inspected vessels....yet ....I think some years, Sea Ray glassed in a huge overboard discharge manifold that had many onboard discharges dump into it. It may eventually blended with an oversized exhaust outlet through the transom. Seemed to work great, lessened though hulls probably for looks as much as anything, and I never heard of an issue with that concept...

But hoses, y's and check valves sound like a bad idea.

Here is the CFR link for commercial vessels and it isn't clear on the y issue with my quick read, but still not likely approved in my mind.

https://www.law.cornell.edu/cfr/text/46/182.520
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Old 07-08-2021, 02:29 PM   #16
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Not sure the USCG regulates anything about or even requires bilge pumps. 33CFR183
Inspected vessels are in title 46, small passenger vessels with more than one bilge pump are required to have a discharge manifold and depending on the size vessel in question number, type and discharge size is stipulated. Generally on inspected boats carrying more than six passengers most inspectors take a dim view of the common Rule type pumps although it isn't stated in CFR.
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Old 07-08-2021, 02:37 PM   #17
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Originally Posted by psneeld View Post
Sorry, now rereading his post I see where he might be headed.

Yes Fish....sharing bilge pump outlets are probably a bad idea and the USCG most likely disallows them on inspected vessels....yet ....I think some years, Sea Ray glassed in a huge overboard discharge manifold that had many onboard discharges dump into it. It may eventually blended with an oversized exhaust outlet through the transom. Seemed to work great, lessened though hulls probably for looks as much as anything, and I never heard of an issue with that concept...

But hoses, y's and check valves sound like a bad idea.

Here is the CFR link for commercial vessels and it isn't clear on the y issue with my quick read, but still not likely approved in my mind.

https://www.law.cornell.edu/cfr/text/46/182.520
I agree it does sound like a bad idea, probably because it is. One of the things I dislike about centrifugal pumps is water can go through them either way, in essence it's a hole in the side of your hull leading straight to the bilge. That's why I use diaphragm pumps and Ultra switches, I also have an 1 1/2" manual diaphragm pump. I'm not too excited about the through the exhaust idea, if you did you'd want a raised syphon break at least several inches above the exhaust elbow.
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Old 07-08-2021, 02:42 PM   #18
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Manifolding diaphragm pumps to a sufficiently large output is safe. I wouldn't do it with centrifugal pumps unless there's no choice and a significant vertical drop from the high point in the hoses to the manifold.
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Old 07-08-2021, 02:48 PM   #19
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Manifolding diaphragm pumps to a sufficiently large output is safe. I wouldn't do it with centrifugal pumps unless there's no choice and a significant vertical drop from the high point in the hoses to the manifold.
Most of the overboard bilge discharge manifolds I've seen have lower and much larger discharge point than the bilge line connections so water can't back up an open unused line. The idea of course is you only open the line or lines currently in use. I'm sure you saw my views on centrifugal pumps.
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Old 07-08-2021, 02:55 PM   #20
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Most of the overboard bilge discharge manifolds I've seen have lower and much larger discharge point than the bilge line connections so water can't back up an open unused line. The idea of course is you only open the line or lines currently in use. I'm sure you saw my views on centrifugal pumps.
Valves on a bilge pump discharge (manifold or otherwise) is entirely unsuitable in my mind. If the pump can't be made automatic or I can't just flip a switch to turn it on, it better be a last resort emergency pump and nothing less. Otherwise it's worthless as a bilge pump.
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