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Old 20-08-2011, 05:10   #31
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Re: Bilge Pump Non-Return Valve

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Originally Posted by PhilK View Post
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.
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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Old 20-08-2011, 06:03   #32
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Re: Bilge Pump Non-Return Valve

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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.
+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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Old 20-08-2011, 06:14   #33
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Re: Bilge Pump Non-Return Valve

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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.
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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Old 08-09-2011, 08:41   #34
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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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Old 08-09-2011, 08:59   #35
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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?
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Old 08-09-2011, 09:11   #36
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Re: Bilge Pump Non-Return Valve

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whatever you do, make sure YOU DO NOT LISTEN TO THE MANUFACTURE! yeesh!! What the hell do they know?
They depend heavily on the K.I.S.S. principle, hoping of course, that the user is the last "S".
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Old 08-09-2011, 09:13   #37
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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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Old 08-09-2011, 09:18   #38
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Re: Bilge Pump Non-Return Valve

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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.
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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Old 08-09-2011, 09:25   #39
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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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Old 08-09-2011, 09:38   #40
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Re: Bilge Pump Non-Return Valve

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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?
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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Old 08-09-2011, 09:45   #41
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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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Old 08-09-2011, 09:46   #42
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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.
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Old 08-09-2011, 09:52   #43
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Re: Bilge Pump Non-Return Valve

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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.
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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Old 08-09-2011, 09:55   #44
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Re: Bilge Pump Non-Return Valve

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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" ;-)
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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Old 08-09-2011, 09:58   #45
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Re: Bilge Pump Non-Return Valve

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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...
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.
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