Check alve - in outlet of the bilge pump - SailNet Community
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post #1 of 12 Old 04-01-2010 Thread Starter
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Check alve - in outlet of the bilge pump

Tell me again why is a bad idea to have a check valve in the bilge pump outlet. Other than it could freeze....
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post #2 of 12 Old 04-01-2010
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why a check valve in bilge pump outlet?

My understanding is 1) it is not needed with a proper loop and 2) it adds resistance and constriction to the outflow.

I just removed mine last week when I replaced the pump.

Or I could be wrong.
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post #3 of 12 Old 04-01-2010
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Velero—

You probably should read the article I wrote on bilge pumps... the problem is that most bilge pumps are the centrifugal RULE type pumps and they don't generate much pressure. If the check valve is in the hose near the pump, it can often get a column of water in the hose beyond it...and the pump may not be able to generate enough pressure to open it against the column of water, preventing the bilge pump from operating correctly.

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Being that your avatar picture is a Hunter 49 I understand the question. On the 49 the back-flow volume from the bilge pump lift is sufficient to cycle the pump continually. The 49 has a pretty deep bilge. I tried a check valve but that had marginal success. The back pressure on the check valve from the water in the hose required the pump work really hard to start flowing. On one occasion the hose from the check valve to the pump blew off and all the pump was doing was pumping right back into the bilge. I dropped the check valve after that. I'm going to try a different switch that has a 20 second delay before turning off. I'll mount the switch about 1/2 inch higher in the bilge. This should stop the cycling of the pump.

Dave
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post #5 of 12 Old 04-01-2010
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I have a check valve in the bilge and a Par Diaphragm Bilge Pump. The combination works well to keep my very small sump dry. I also have a 1500 Rule, an alarm and a manual pump for when things go wrong.

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post #6 of 12 Old 04-01-2010 Thread Starter
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Brezzin that is exactly my problem. I did upgraded the bp from the 1500 to the 3700 model. I got a new switch comming in, but bought the check valve so I am going to try it and see if it works with the larger pump.
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post #7 of 12 Old 04-01-2010
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I don't see why you cant have "maintenance" pump, usually a small one, with a check valve...then another "emergency" pump of larger size mounted above or near it with out a check valve?

I have a Rule 500 mounted low in the bilge with a check valve and 3" above that is a Rule 3700 with smooth hose and no check valve. This keeps the water level in the bilge low or dry (I get some rain water in through the keel step mast). The large one is kept high and dry and hopefully will last a very long time

I would add that the larger pump is wired directly to the house batteries, the smaller is on a switch. This way I can never accidentally switch off the big daddy.

As for the freezing concerns...I add some antifreeze (pink stuff) to the bilge in the winter and switch the little one off after running a bit of the antifreeze through it. I check the boat every couple of weeks and cycle it if need be. Its also a good way to check if there is a leak somewhere. If the pump is continuously operating while I'm not there I wouldn't know of a slow leak unless I have a counter installed.

Cheers,
Shawn

S/V Windgeist
1982 Tartan 37C

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Last edited by T37Chef; 04-01-2010 at 02:20 PM.
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post #8 of 12 Old 04-01-2010
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instead of having a maintenance pump with a check valve in the line, just have a very small maintenance pump. It will minimize the water that backflushes into the bilge.

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Originally Posted by T37Chef View Post
I don't see why you cant have "maintenance" pump, usually a small one, with a check valve...then another "emergency" pump of larger size mounted above or near it with out a check valve?

I have a Rule 500 mounted low in the bilge with a check valve and 3" above that is a Rule 3700 with smooth hose and no check valve. This keeps the water level in the bilge low or dry (I get some rain water in through the keel step mast). The large one is kept high and dry and hopefully will last a very long time

I would add that the larger pump is wired directly to the house batteries, the smaller is on a switch. This way I can never accidentally switch off the big daddy.

As for the freezing concerns...I add some antifreeze (pink stuff) to the bilge in the winter and switch the little one off after running a bit of the antifreeze through it. I check the boat every couple of weeks and cycle it if need be. Its also a good way to check if there is a leak somewhere. If the pump is continuously operating while I'm not there I wouldn't know of a slow leak unless I have a counter installed.

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—Cpt. Mal Reynolds, Serenity (edited)

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post #9 of 12 Old 04-01-2010
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I have a small flojet pump I was going to mount inline with the discharge line, with a rule float switch, to activate, this should work yes?...

Red, 77 Jeanneau Gin Fizz 38
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post #10 of 12 Old 04-01-2010
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A flojet pump doesn't require a check valve, because it already has them integrated as part of the diaphragm pump.

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Originally Posted by redhead78 View Post
I have a small flojet pump I was going to mount inline with the discharge line, with a rule float switch, to activate, this should work yes?...

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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
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