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  #11  
Old 11-13-2012
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Quote:
Originally Posted by MastUndSchotbruch View Post
BUT: I had never thought of doing what Hartley suggests:

"install it high up near the discharge point - not in the bilge with the pump itself"

In that case, you do NOT have the water column keeping the valve stuck in closed. That seems to me the smart way to do it (why didn't I think of that?).

Next time I have a chance, I will try that on my installation.
Won't that still keep the column of water in the hose as the valve will create vacuum as the water tries to drain out of the hose?

I have check valves on my lines, but I use two pumps with impellers and they have enough force to push the column of water out. Still, after this thread I am going to replace them with vented loops as I want better reliability.

My plan is to as close to the pump as possible, and try to get the loop as high as I can. My outlets are right below the hull/deck joint, and I'm not entirely sure I can get the vented loops that high... is that going to be an issue?
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  #12  
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Re: Bilge pump non return valve.

Quote:
Originally Posted by Maine Sail View Post
But that pretty much defeats the entire purpose of the check valve. A siphon break is still a choice that won't stick closed. If you are not preventing hose drain back then there is little point for a check valve...... Bilge pump hoses should always be installed to prevent back siphoning which includes a high loop and a siphon break....
Of course you are entirely right, as far as boats and bilges are concerned.

I know I may be a bit off-topic here, this being sailnet, but as I mentioned, my application is not on a boat. I need to pump some water uphill but in my case there is no possibility that a siphoning situation develops. My problem is only that the hose is long, and the water that runs back will cycle the pump again. If I can prevent the hose emptying (or at least slow it down significantly), that will solve the cycling problem.

Seems to me that for my particular situation, a check valve close to the top end might solve the problem. Glad I read this thread, I never had thought about it.

Last edited by MastUndSchotbruch; 11-13-2012 at 11:10 AM. Reason: typo
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Old 11-13-2012
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Re: Bilge pump non return valve.

Quote:
Originally Posted by Maine Sail View Post
But that pretty much defeats the entire purpose of the check valve. A siphon break is still a choice that won't stick closed. If you are not preventing hose drain back then there is little point for a check valve...... Bilge pump hoses should always be installed to prevent back siphoning which includes a high loop and a siphon break....
Agreed, you need to prevent back siphoning which includes a high loop and a siphon break.. but you're quite wrong about having the check valve up high defeating the purpose. Hose drain back is irrelevant - it's, what, 1 litre of water max?

Think about what happens when you put the gunnel under on a flush-deck boat with the bilge pump exit out of the side just above the waterline - even with a high loop and a siphon break.

Boats have sunk because of that.
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Old 11-13-2012
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Re: Bilge pump non return valve.

Quote:
Originally Posted by Hartley18 View Post
Agreed, you need to prevent back siphoning which includes a high loop and a siphon break.. but you're quite wrong about having the check valve up high defeating the purpose. Hose drain back is irrelevant - it's, what, 1 litre of water max?

Think about what happens when you put the gunnel under on a flush-deck boat with the bilge pump exit out of the side just above the waterline - even with a high loop and a siphon break.

Boats have sunk because of that.
What is "quite wrong" is an installation like you state.. Sorry but I can't fix an improperly designed bilge pump system. As I said and was discussing in a "PROPERLY" designed bilge pumping system, which on sailboats does NOT include placing the exit where it will go under water under heel and can't be protected by a siphon break, there is no need for a check valve.

Sorry but if you have a boat designed like this to rely on a $0.50 piece of rubber flapper is just crazy. The US ABYC recognizes this and specifically prohibits check valves used for this purpose. This is a situation that requires surgery, don't put a Band-Aid on it.

An installation such as that does not meet even the basic safety standards.


ABYC:
22.8.6 The discharge location shall be above the
maximum heeled waterline, or

22.8.7 the discharge may be located below the
maximum heeled waterline if the discharge line is provided
with both of the following:

22.8.7.1 a seacock installed in accordance with the
requirements of ABYC H-27, Seacocks, Thru-Hull
Connections, and Drain Plugs, and

22.8.7.2 a vented loop or other means to prevent
siphoning into the boat. A check valve shall not be used for
this purpose.
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Last edited by Maine Sail; 11-13-2012 at 10:28 PM.
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  #15  
Old 11-13-2012
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Re: Bilge pump non return valve.

So, in your opinion, out the stern is the only suitable location for a bilge pump exit?

..or do you have some other system in mind??
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Old 11-13-2012
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Re: Bilge pump non return valve.

Just to clarify ... we only talking electric pumps here ?

Our manual emergency pump (Henderson type) has been unused for many years and I suspect that its rubber flappy thing has perished. Yes there is a seacock on the through hull.

I'm about ready to rebuild the thing but what of adding a check valve into the line as back up ? Is this OK ? Is this stupid ? Is this simply not necessary ?
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Old 11-14-2012
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Re: Bilge pump non return valve.

Quote:
Originally Posted by Hartley18 View Post
So, in your opinion, out the stern is the only suitable location for a bilge pump exit?

..or do you have some other system in mind??
No, I have seen perfectly suitable stern quarter outlets, bow and even side discharges with a center-line siphon break and a shut off seacock... I do prefer the stern though as do many builders who try and do it right..

Side discharges are my least favorite and I would personally avoid them at all costs on a sailboat. The proper installation of the siphon break gets difficult and can leave exposed hose visible in the cabin, to do a "safe" install for a side discharge..

Bilge pumps to me are not an "after thought" they can be a safety item and one that should be taken seriously. Having had a thru-hull fitting snap, another story for another day, I do take bilge pumps and proper installation techniques seriously.

My main objection is using a check valve to keep your vessel afloat. But I am not alone on this and the ABYC concurs.. My only beef is the use of check valves on a primary bilge pump when that pump is also a centrifugal/Rule type.

I have less issues with them on rotary vane or diaphragm pumps because they CAN open them where the centrifugal often won't...
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  #18  
Old 11-14-2012
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Re: Bilge pump non return valve.

Quote:
Originally Posted by tdw View Post
Just to clarify ... we only talking electric pumps here ?

Our manual emergency pump (Henderson type) has been unused for many years and I suspect that its rubber flappy thing has perished. Yes there is a seacock on the through hull.

I'm about ready to rebuild the thing but what of adding a check valve into the line as back up ? Is this OK ? Is this stupid ? Is this simply not necessary ?

Those Henderson pumps can suck Bigfoots turds through a straw. No issues with a check valve on those but do use an intake screen on the pick up..

Again the real concern is with a "Rule" type centrifugal pump and the use of a check valve. These pumps have very little ability to deal with restricted or increased head pressure before they just sit there and make tiny bubbles and kill your bank..
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  #19  
Old 11-14-2012
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Re: Bilge pump non return valve.

Well then I'll keep well clear of Bigfoot country .....

Intake screen already in place.

Thanks MS.
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Old 11-14-2012
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Re: Bilge pump non return valve.

Quote:
Originally Posted by Maine Sail View Post
No, I have seen perfectly suitable stern quarter outlets, bow and even side discharges with a center-line siphon break and a shut off seacock... I do prefer the stern though as do many builders who try and do it right..

Side discharges are my least favorite and I would personally avoid them at all costs on a sailboat. The proper installation of the siphon break gets difficult and can leave exposed hose visible in the cabin, to do a "safe" install for a side discharge..
I totally agree - but in an older boat there is not always a choice. If you hadn't guessed already, my suggested use of the check valve for a side discharge is to act as a 'flapper' to keep water coming back into the boat when heeled and the bilge pump is not running.. you still need the loop and siphon break.

Since the valve spends most of it's life above the water-line, there is no columns of water either side to hold it closed and the biggest risk is it perishing and failing open. Believe me, it's far better than having the boat threaten to sink under you.

Discharge into the cockpit is looking better all the time!

Quote:
Originally Posted by Maine Sail View Post
Bilge pumps to me are not an "after thought" they can be a safety item and one that should be taken seriously. Having had a thru-hull fitting snap, another story for another day, I do take bilge pumps and proper installation techniques seriously.

My main objection is using a check valve to keep your vessel afloat. But I am not alone on this and the ABYC concurs.. My only beef is the use of check valves on a primary bilge pump when that pump is also a centrifugal/Rule type.
I wouldn't like to suggest anyone relying on a check valve to keep your vessel afloat. For that reason, installation down in the bilge (as a 'foot valve') is a really bad idea!

Quote:
Originally Posted by Maine Sail View Post
I have less issues with them on rotary vane or diaphragm pumps because they CAN open them where the centrifugal often won't...
In my experience rotary vane or diaphragm pumps are more likely to blow the hose-end off the check valve if it fails to open... but if you are going to use them just make sure your piping can handle the output pressure, 'tis all.
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