Bilge pump impeller working, but not pumping

[Ralph Johnstone]

Hey guys, let's not kill us messengers....

No, no, no. Not kill him, just shake him up a little and give him a few sleepless nights. !

I'm the first to agree that bilge pumps shouldn't have check valves as you don't want crap and corruption plugging the discharge line. However, if you've got a great long discharge line which has enough volume to restart the pump as it backflows into the bilge after shutting down, you may want a check valve in there as a last resort. Personally, I'd move heaven and earth to come up with an alternative solution to a check valve.

one should never use a check valve with centrifugal pumps. Never, no matter the reason.

I'm assuming you meant bilge pumps when you said centrifugal pumps. At the time I just thought "every cetrifugal pump on the face of the earth ?"

I also find it a great impediment to talk without using my hands :

 

[dlochner]

At some of the current crop of Rule Bilge pumps have a check valve at the pump. It looks sort of like a small joker valve and fits in the pumps outlet.

 

[kappykaplan]

Does Rule even make any pumps other than centrifugal?????

Like I said in post 12, I'll check the documentation the next time I'm on the boat. I seriously didn't think my pumps were centrifugal.

 

[capta]

Personally, I'd move heaven and earth to come up with an alternative solution to a check valve.

Simplest way I can think of to accomplish that is with a high loop and anti-suction valve as close to the pump as possible.
It might take some creative thinking, but it should be doable on most boats.

 

[FastOlson]

@capta , they are both standard Rule pumps and not centrifugal.

By design, a Rule bilge pump is (normally) a centrifugal pump. Cheap to buy, but their useful real-world GPH pumping ability is overrated enthusiastically on the brightly colored box. Many years ago Practical Sailor did a test of bilge pumps and ratted them out.... But inexperienced boaters still buy them solely because they are cheap.
P.T. Barnum was right, unfortunately.

Since the practical use of a bilge pump is to remove nuisance water, and you'd also like to avoid back flooding, just install a way-superior pump, like the long-produced model Jabsco 37202-0000.
Note B: please have a high loop on the discharge hose before it reaches the transom fitting.

 

[kappykaplan]

long-produced model Jabsco 37202-0000.

I'll keep this in mind for the next time I have to replace - still have two new spare Rule pumps on the boat.

 

[dlochner]

By design, a Rule bilge pump is (normally) a centrifugal pump. Cheap to buy, but their useful real-world GPH pumping ability is overrated enthusiastically on the brightly colored box. Many years ago Practical Sailor did a test of bilge pumps and ratted them out.... But inexperienced boaters still buy them solely because they are cheap.
P.T. Barnum was right, unfortunately.

Since the practical use of a bilge pump is to remove nuisance water, and you'd also like to avoid back flooding, just install a way-superior pump, like the long-produced model Jabsco 37202-0000.
Note B: please have a high loop on the discharge hose before it reaches the transom fitting.

The Jabsco 37202-0000 is a diaphragm pump that pulls and then pushes water unlike a centrifugal pump that can only push water. A similar pump is the Whale Bilge IC. These pumps have an additional advantage in that they are not mounted in the bilge and not subject to being submerged. The Whale pump has been installed on Second Star for about 5 years with no problems.

 

[kappykaplan]

The Whale pump has been installed on Second Star for about 5 years with no problems.

Dave, do you have any photos of your installation? I'm curious. Tks.

 

[dlochner]

Dave, do you have any photos of your installation? I'm curious. Tks.

Sorry I don't. There was space just aft of the engine compartment past the stuffing box. I built a small shelf there and mounted the pump on the shelf. A ¾" hose ran forward, under the engine and into the aft and deepest spot in the bilge. The out let went aft from the pump, up a loop and down and out through a low discharge outlet on the transom. On the whale, the water sensor is built into the strum box.

 

[kloudie1]

History note, my experience. The H-34 has a very shallow bilge and they were supplied from Hunter with a centrifugal Rule 2000 GPH (nominal) and a 1 1/8" check valve in the discharge line. The discharge line is about 12 feet long with a rise of about 5 feet and exits just under the toe rail. Should the check valve leak, the volume in the hose is such that it will fill the bilge enough to trigger the float switch . Not optimal but I have had one leaking valve problem in the 31 years that I've owned the boat. That problem was a piece of insulation stripped from an 18 gauge wire.. The little bit of insulation stuck in the valve seat and caused a slow backflow. I cleaned the valve and returned it to service. I generally keep a clean bilge but not dry. The dehumidifier runs all the time (no off season here) so there is condensate water (almost distilled, fresh) that is always there .. The pump and check are original to the boat so they have been in service for 37 years. Yes I carry a spare pump, check valve, and float switch. What I have works OK for me.
I understand the concern about the check valve, but most diaphragm pumps have a discharge check valve in them to allow them to function. That valve is quite small compared to a 1 1/8" valve and can be fouled much easier; note that many of the diaphragm pumps come with a strainer.. The centrifugals typically have a strainer built into the base and can pass debris much larger than would be passable through the diaphragm pump discharge valve. There are some kinds of bilge pumps that kinda work without a check of any kind, but they are typically more expensive and typically less efficient than centrifugal or diaphragm types. My buddy's older Tartan 37 had a flex rubber impeller type bilge pump (like a raw water pump on the engine) that dried the bilge well and prevented backflow. Something like this
1/10 HP Transfer Pump 320 GPH (harborfreight.com)
Not saying that one, something like that.. could be used to eliminate a bilge pump check valve. It is a flex rubber impeller type pump.
My 2.6 cents worth.. (2 cents plus our current 30% inflation rate on many things.)

 

[JamesG161]

A deceptive marketing plan is to report the pump's capacity at zero head.

Sorry Dave this is NOT true.

All centrifugal pumps are shown at Dead Head pressures or Zero Flow, not Zero Head.

Jim...

 

[JamesG161]

If you want more information by @Maine Sail and me read this post

Bilge Pumps 101

We did a full discussion on Centrifugal Bilge Pumps. Pump curves and all.
Jim...

 

[Scott T-Bird]

I also have a diaphragm pump Jabsco Model #: 31705-0092. I like it far more than the centrifugal pumps. There is a strainer just upstream from the pump where it is easy to access and clean. I just have a 3/4" hose in the bilge. The only instance it fails to pick up water is when the strainer gets clogged. A separate float switch operates the pump automatically (when I have it mounted properly).

 

[JamesG161]

The only instance it fails to pick up water is when the strainer gets clogged.

or when one of the diaphragms wears out.
Keep that strainer clean too.
Jim...

 

[Scott T-Bird]

or when one of the diaphragms wears out.
Keep that strainer clean too.
Jim...

Yes, I replaced the pump that came with the boat in our first season for that very reason ...

 

[Lee Hadjiosif]

When you take the hose off the pump, blow air through it with your mouth, and feel if there is any resistance. You should be able to blow through it easily. I would of course clean the end first or place a plastic food wrap around it with a hole in the middle.

 

[John_F]

I agree with Ralph. I have work on and tested pumps for over 40 years and the first thing I ask when I purchased a sailboat was "Why in the world is there no check valve on the bilge pump? It lets a gallon of water return to the bilge every time it shuts off."

I didn't install the pump or the hoses. Everything came with the boat. It's a Rule Mate 750.

 

[John_F]

Try checking to see if the impeller is slipping on the motor spindle under load.

Thanks,, it definitely works when I placed in a bucket with water. The odd thing is that altough the motor works, it doesn't pump water once it's back in the bilge so it might be something with the check valve in the hose. Thank.s

 

[Dalliance]

my pump will be replaced for similar issues; look like the tabs on the housing are loose. If I push down slightly on the housing it will pump better.

I’ve had some occasional problems with my primary bilge pump not drawing water recently. Did a forum search and your comment from two years ago was something I hadn’t thought of yet. I pressed down on the pump and confirmed that’s the issue. Thanks.
It’s a Rule 800 pump I installed 17 years ago, so I got my money’s worth out of it. I wonder if the 2014 Rule pumps are the same quality they were in 2007.