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Old 20-11-2018, 15:59   #1
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How connect two bilge pumps to ione thru hull

Want to eliminate one thru hull.


Right now each bilge pump has its own thru hull.


Was thinking of eliminating one by having each pump go to a sea chest then the sea chest goes to the thru hull.


What are others doing ?


How else can I eliminate one thru hull ?


maybe by having one pump go to the cockpit ?


Thanks


jim
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Old 20-11-2018, 16:17   #2
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Re: how connect two bilge pumps to ione thru hull

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Originally Posted by xxhat View Post
Want to eliminate one thru hull.


Right now each bilge pump has its own thru hull.


Was thinking of eliminating one by having each pump go to a sea chest then the sea chest goes to the thru hull.


What are others doing ?


How else can I eliminate one thru hull ?


maybe by having one pump go to the cockpit ?


Thanks


jim
I’ve always been keen on dropping the emergency (higher in bilge) pump into the cockpit, that way you have a kiss built in alarm if the water is rising or when it is subsiding.
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Old 20-11-2018, 18:13   #3
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Re: how connect two bilge pumps to ione thru hull

I would be leary of having a bilge pump discharge to the cockpit on my boat, if the water is coming in because one of the through hulls for a cockpit drain failed it would only be recirculating water and not buying me time to do something about the leak. But I'm paranoid-obsessive in matters of damage control... On the same vien you could possibly rig it to discharge out of the outboard edge of the coaming...
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Old 20-11-2018, 18:19   #4
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Re: how connect two bilge pumps to ione thru hull

you would need non return valves after each bilge pump before the two hoses tee together to a single hose to the skin fitting
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Old 20-11-2018, 18:22   #5
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Re: how connect two bilge pumps to ione thru hull

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you would need non return valves after each bilge pump before the two hoses tee together to a single hose to the skin fitting
Oh no! The dreaded non-return debate is about to begin. Makes guns and anchors seem like a sewing circle discussion.

I'm getting myself a spot on the fence.
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Old 20-11-2018, 19:38   #6
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Re: how connect two bilge pumps to ione thru hull

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Originally Posted by SV_Harbinger View Post
I would be leary of having a bilge pump discharge to the cockpit on my boat, if the water is coming in because one of the through hulls for a cockpit drain failed it would only be recirculating water and not buying me time to do something about the leak. But I'm paranoid-obsessive in matters of damage control... On the same vien you could possibly rig it to discharge out of the outboard edge of the coaming...
I have two thru hills servicing my cockpit via 4 scuppers both of which o can inspect from the cockpit locker. My through is at least you’d know something was up before it came over the sole. Alarms are also an option.
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Old 20-11-2018, 19:41   #7
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Re: how connect two bilge pumps to ione thru hull

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Oh no! The dreaded non-return debate is about to begin. Makes guns and anchors seem like a sewing circle discussion.

I'm getting myself a spot on the fence.
You think that’s entertaining? Someone started an ‘exterior varnish’ thread, better get over there and claim a seat lol
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Old 20-11-2018, 19:44   #8
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Re: how connect two bilge pumps to ione thru hull

If you ever needed both pumps at the same time the discharge would be limited by the size of the skin fitting.

The sea chest is a bad idea; you would have to make it large enough to handle the flow of both pumps and tall enough that the level never reaches the input lines from the pumps. How would you empty it? A third bilge pump? Or rely on the current pumps to pressurize the chest? Which would never work.

With check valves on each line one pump could turn off the flow of the other.

Bilge pump systems should be as simple as possible. Maybe you should check the ABYC standards for bilge pumps and share your idea with your insurance company.
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Old 20-11-2018, 19:52   #9
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Re: how connect two bilge pumps to ione thru hull

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If you ever needed both pumps at the same time the discharge would be limited by the size of the skin fitting.

The sea chest is a bad idea; you would have to make it large enough to handle the flow of both pumps and tall enough that the level never reaches the input lines from the pumps. How would you empty it? A third bilge pump? Or rely on the current pumps to pressurize the chest? Which would never work.

With check valves on each line one pump could turn off the flow of the other.

Bilge pump systems should be as simple as possible. Maybe you should check the ABYC standards for bilge pumps and share your idea with your insurance company.
I reckon the sea chest would work just fine, reasonably tall, pumps emptying into top with a large skin fitting plumbed to the bottom.The gravity monster will prevail.
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Old 20-11-2018, 21:31   #10
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Re: how connect two bilge pumps to ione thru hull

Since most bilges have at least a little bit of oil in them, having a pump come into the cockpit could easily end up with someone having a broken hip or ankle. Oil (any at all) in the cockpit will cause a disaster. Think about it. ____Grant.
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Old 20-11-2018, 22:19   #11
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Re: how connect two bilge pumps to ione thru hull

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Originally Posted by xxhat View Post
Want to eliminate one thru hull.


Right now each bilge pump has its own thru hull.


Was thinking of eliminating one by having each pump go to a sea chest then the sea chest goes to the thru hull.


What are others doing ?


How else can I eliminate one thru hull ?


maybe by having one pump go to the cockpit ?


Thanks


jim
To what end?

Your bilge pumps are the most critical system on the boat. Don't mess with them.
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Old 20-11-2018, 22:20   #12
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Re: how connect two bilge pumps to ione thru hull

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I reckon the sea chest would work just fine, reasonably tall, pumps emptying into top with a large skin fitting plumbed to the bottom.The gravity monster will prevail.
I reckon you haven't thought this through.
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Old 20-11-2018, 23:10   #13
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Re: how connect two bilge pumps to ione thru hull

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I reckon you haven't thought this through.
You may be correct, or not. The concept of a sea chest is that one hull perforation below waterline supplies water to all equipment requiring sea water to operate from the one point, sized appropriately. If one transfers that principle to discharge, in this case bilge pump discharge which would normally be installed approx 150-200 mm above nominal waterline and installed a chest (or tank or whatever you choose to call it) higher than this, with a free flowing through hull fitting of an appropriate size fitted below and the bilge pumps emptying into the top of this chest or tank or whatever you choose to call it then the principle would be that all water pumped into said chest or tank or whatever would simply drain overboard.
As you said I may not have thought it through, or perhaps you simply do not understand the concept.
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Old 20-11-2018, 23:20   #14
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Re: how connect two bilge pumps to ione thru hull

Okay.

The sea chest is 200mm above the waterline. You forget to turn on your bilge pump and you get a serious leak. Your boat sinks 210mm. Your bilge pumps will now spray sea water everywhere.

But wait...You installed check valves....Doesn't matter because the bilge pumps can't pump against the pressure of the sea water.
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Old 20-11-2018, 23:46   #15
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Re: how connect two bilge pumps to ione thru hull

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Okay.

The sea chest is 200mm above the waterline. You forget to turn on your bilge pump and you get a serious leak. Your boat sinks 210mm. Your bilge pumps will now spray sea water everywhere.

But wait...You installed check valves....Doesn't matter because the bilge pumps can't pump against the pressure of the sea water.
Firstly, if you have forgotten to turn on your bilge pump how will it spray sea water everywhere, and just where did I even mention check valves.
Ignorance reins supreme!!
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