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20-08-2011, 04:10
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#31
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Registered User
Join Date: Oct 2010
Location: Avalon, NJ
Boat: Albin 40 double cabin Trawler
Posts: 1,886
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Re: Bilge Pump Non-Return Valve
Quote:
Originally Posted by PhilK
Well Whale (manufacturer of centrifugal type pumps) clearly disagree with you - and they should be experts.
Another solution might be to reroute the hose to go vertical to start with and fit an anti-siphon bend so that only the short vertical length back fills. It may not be practicable though seeing that the original installation was "involved".
Rule say that reducing the hose diameter is acceptable (will just reduce the capacity). Reducing the hose to 38mm will reduce the back flow by approximately 40% which should effectively stop the problem.
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they are the ones who grossly overstate thrier pumps capabilities...
only in the fine print do you see where any restriction or head eats into performance drastically...look it up if you don't believe me.
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20-08-2011, 05:03
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#32
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Registered User
Join Date: Dec 2008
Location: St. Georges, Bda
Boat: Rhodes Reliant 41ft
Posts: 4,131
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Re: Bilge Pump Non-Return Valve
Quote:
Originally Posted by psneeld
they are the ones who grossly overstate thrier pumps capabilities...
only in the fine print do you see where any restriction or head eats into performance drastically...look it up if you don't believe me.
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+1 Which is why I offered a compromise suggestion in my earlier posts.
Actually, when you get into pump design, many factors enter, open or closed impeller, tolerences betweem impellor and pump chamber walls, stripping edge and volute design, anti- coriolis vanes, etc.
Simple fact-bigger is better as long as the batteries are good.
__________________
so many projects--so little time !!
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20-08-2011, 05:14
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#33
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Registered User
Join Date: Oct 2010
Location: Avalon, NJ
Boat: Albin 40 double cabin Trawler
Posts: 1,886
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Re: Bilge Pump Non-Return Valve
Quote:
Originally Posted by Blue Stocking
+1 Which is why I offered a compromise suggestion in my earlier posts.
Actually, when you get into pump design, many factors enter, open or closed impeller, tolerences betweem impellor and pump chamber walls, stripping edge and volute design, anti- coriolis vanes, etc.
Simple fact-bigger is better as long as the batteries are good.
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bigger isn't better if installed poorly...that's the rub...boaters are mislead by the pumping capacity printed on the pump then they mount it is poor places with long runs and many turns...or with fittings that neck down...or with check valves that neck down AND induce back pressure...and now that pumpong capacity could be half of the rated capacity (granted that would be a really poor install).
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08-09-2011, 07:41
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#34
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Registered User
Join Date: Sep 2011
Boat: Tartan 3400
Posts: 6
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Re: Bilge Pump Non-Return Valve
Fascinating discussion here. I'm wondering if anyone knows of an actual case where a non-return valve failure has actually sunk or endangered a boat? Maybe I missed it, but I didn't see any actual examples in the discussion. Or is this just an abstract possibility that some people would like to eliminate or avoid if possible? Thanks.
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08-09-2011, 07:59
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#35
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Registered User
Join Date: Mar 2006
Posts: 1,594
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Re: Bilge Pump Non-Return Valve
whatever you do, make sure YOU DO NOT LISTEN TO THE MANUFACTURE! yeesh!! What the hell do they know?
__________________
Randy
Cape Dory 25D Seraph
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08-09-2011, 08:11
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#36
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Registered User
Join Date: Dec 2008
Location: St. Georges, Bda
Boat: Rhodes Reliant 41ft
Posts: 4,131
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Re: Bilge Pump Non-Return Valve
Quote:
Originally Posted by rtbates
whatever you do, make sure YOU DO NOT LISTEN TO THE MANUFACTURE! yeesh!! What the hell do they know?
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They depend heavily on the K.I.S.S. principle, hoping of course, that the user is the last "S".
__________________
so many projects--so little time !!
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08-09-2011, 08:13
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#37
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Registered User
Join Date: Sep 2011
Boat: Tartan 3400
Posts: 6
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Re: Bilge Pump Non-Return Valve
Is the sarcasm necessary? The issue is that some manufacturers (e.g. Johnson, Whale) *recommend* no-return/check valves while other manufacturers (e.g. Rule) recommend against them. Yet many observers feel it is never wise to use them (while others feel it's not a problem at all). It sounds like you may be in the "never use them" camp, but you could just as easily be in the "just do whatever the manufacturer or your pump says" camp. Either way, I don't much care, and that wasn't my question.
My question was whether anyone knew of actual cases where a boat sank or was endangered because of a failed check valve? Thanks.
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08-09-2011, 08:18
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#38
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Registered User
Join Date: Oct 2010
Location: Avalon, NJ
Boat: Albin 40 double cabin Trawler
Posts: 1,886
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Re: Bilge Pump Non-Return Valve
Quote:
Originally Posted by rlmmail
Is the sarcasm necessary? The issue is that some manufacturers (e.g. Johnson, Whale) *recommend* no-return/check valves while other manufacturers (e.g. Rule) recommend against them. Yet many observers feel it is never wise to use them (while others feel it's not a problem at all). It sounds like you may be in the "never use them" camp, but you could just as easily be in the "just do whatever the manufacturer or your pump says" camp. Either way, I don't much care, and that wasn't my question.
My question was whether anyone knew of actual cases where a boat sank or was endangered because of a failed check valve? Thanks.
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If you think boating manufacturers know more than lifelong boaters/cruisers then be my guest...all you have to do is spend some time at a boat show listening to manufacturer/builder reps and old timers (of course the ones with brains and experience...not all)...and you will quickly know who is in the know.....
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08-09-2011, 08:25
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#39
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Registered User
Join Date: Sep 2011
Boat: Tartan 3400
Posts: 6
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Re: Bilge Pump Non-Return Valve
Again, it's not a matter of manufacturers vs. lifelong cruisers--clearly there are members of *both* groups are on *both* sides of this issue. That kind of "analysis" clearly cannot resolve the issue.
What I'm wondering is whether there are empirical examples of a boat sinking or being endangered because of a failed check valve?
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08-09-2011, 08:38
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#40
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Registered User
Join Date: Oct 2010
Location: Avalon, NJ
Boat: Albin 40 double cabin Trawler
Posts: 1,886
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Re: Bilge Pump Non-Return Valve
Quote:
Originally Posted by rlmmail
Again, it's not a matter of manufacturers vs. lifelong cruisers--clearly there are members of *both* groups are on *both* sides of this issue. That kind of "analysis" clearly cannot resolve the issue.
What I'm wondering is whether there are empirical examples of a boat sinking or being endangered because of a failed check valve?
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It's not about failure as it is about greatly reducing capacity of the pump...properly installed bilge pumps (really your whole system) don't need them....there's NO 2 camps...the checkvalves CLEARLY redude capacity because of the backpressure which is equivalent to "head"...
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08-09-2011, 08:45
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#41
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Registered User
Join Date: Sep 2011
Boat: Tartan 3400
Posts: 6
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Re: Bilge Pump Non-Return Valve
If a check valve failed in the shut position, then a boat could presumably sink or be endangered. I certainly think it would be relevant to know if that has ever happened, no? But it sounds as if you, at least, don't consider that a real danger. I suspect many others might, because that's the only way to explain how adamant and dire the "no check valve" camp can get at times. And maybe they're right. I'm just trying to figure that out through empirical examples rather than through sarcasm and name-calling.
As for reduced capacity, your point is well taken. I get that. On the other hand, if a pump's battery is run down because of backflow-induced recycling, then that too constitutes a rather extreme form of "reduced capacity" ;-)
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08-09-2011, 08:46
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#42
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Registered User
Join Date: Dec 2008
Location: St. Georges, Bda
Boat: Rhodes Reliant 41ft
Posts: 4,131
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Re: Bilge Pump Non-Return Valve
In answer to your specific wording,--NO, but many years ago, worked for a Penn Yan outboard runabout operation. Submersible pump was in a sump under engine, with no room to for a high riser loop. Bilge pump outlet was 3" above waterline. Battery flat, boat would backfill.
After 3 of these incidents, we fitted non-returns at pump and informed new owners.
Here, the after market fitting saved the boat.
__________________
so many projects--so little time !!
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08-09-2011, 08:52
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#43
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Registered User
Join Date: Oct 2010
Location: Avalon, NJ
Boat: Albin 40 double cabin Trawler
Posts: 1,886
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Re: Bilge Pump Non-Return Valve
Quote:
Originally Posted by Blue Stocking
In answer to your specific wording,--NO, but many years ago, worked for a Penn Yan outboard runabout operation. Submersible pump was in a sump under engine, with no room to for a high riser loop. Bilge pump outlet was 3" above waterline. Battery flat, boat would backfill.
After 3 of these incidents, we fitted non-returns at pump and informed new owners.
Here, the after market fitting saved the boat.
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poorly designed bilge pump setup...one should be a dry pump for rainwater, routine pumping...large capacity for more serious issue..one not needing the loop...
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08-09-2011, 08:55
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#44
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Registered User
Join Date: Oct 2010
Location: Avalon, NJ
Boat: Albin 40 double cabin Trawler
Posts: 1,886
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Re: Bilge Pump Non-Return Valve
Quote:
Originally Posted by rlmmail
If a check valve failed in the shut position, then a boat could presumably sink or be endangered. I certainly think it would be relevant to know if that has ever happened, no? But it sounds as if you, at least, don't consider that a real danger. I suspect many others might, because that's the only way to explain how adamant and dire the "no check valve" camp can get at times. And maybe they're right. I'm just trying to figure that out through empirical examples rather than through sarcasm and name-calling.
As for reduced capacity, your point is well taken. I get that. On the other hand, if a pump's battery is run down because of backflow-induced recycling, then that too constitutes a rather extreme form of "reduced capacity" ;-)
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never inferred that wasn't an issue... but no boat should rely on one pump...that's a newbie issue so I didn't address it...bact to my ststement about listening to the people in the know...not necessarily what you learn from bosatshows and internet forums....
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08-09-2011, 08:58
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#45
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Registered User
Join Date: Dec 2008
Location: St. Georges, Bda
Boat: Rhodes Reliant 41ft
Posts: 4,131
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Re: Bilge Pump Non-Return Valve
Quote:
Originally Posted by psneeld
poorly designed bilge pump setup...one should be a dry pump for rainwater, routine pumping...large capacity for more serious issue..one not needing the loop...
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Take a look at an old Penn Yan, 14-16ft, with a molded in floor, and a small sump under the engine. You'll see what I meen.
__________________
so many projects--so little time !!
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