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Bilge pump non return valve.

50K views 61 replies 27 participants last post by  smurphny 
#1 ·
Someone recommended that I install a non return valve on my automatic bilge pump. As a result I ordered one and installed it. BIG MISTAKE. The first time I tested it the valve stuck and would not allow the water to pump out. Its now gone. After I pumped the bilge there was no flow back through the pump back into the bilge.
 
#3 ·
As Maine Sail says, it's a mistake to install a check valve in line with a centrifugal bilge pump (e.g., Rule pumps). The pump can move a lot of water but doesn't have much power. Think of it as high voltage, low amperage. Use a Vented Loop instead.

The PO of our boat installed a check valve and the bilge pump never really worked. I fussed with it for the first few months of ownership until the bilge filled and the battery drained when the pump ran in a vain attempt to move the water. I installed a vented loop and haven't thought of it in 7 years.
 
#7 ·
As Maine Sail says, it's a mistake to install a check valve in line with a centrifugal bilge pump (e.g., Rule pumps). The pump can move a lot of water but doesn't have much power. Think of it as high voltage, low amperage. Use a Vented Loop instead.

The PO of our boat installed a check valve and the bilge pump never really worked. I fussed with it for the first few months of ownership until the bilge filled and the battery drained when the pump ran in a vain attempt to move the water. I installed a vented loop and haven't thought of it in 7 years.
If I install a vented loop in my discharge line, should be closer to the pump, or to the point of discharge?
 
#4 ·
It's not quite as simple as no check valve on centrifugal pumps. A great many centrifugal pumps MAY use a check valve (or foot valve, as they are called when installed directly into the pump outlet. Most sump pump and condensate pump installations use a check or foot valve.

It's just that the typical 12 volt bilge pump for small boats has very low head capacity. The tradeoff is between flow and head, as it is on all centrifugal pumps. Higher head = lower flow, and vice versa.
 
#5 · (Edited)
These valves quite often stick shut especially if the bilge pump does not cycle often. The biggest draw back is the added head pressure that the pump can not overcome. This additional head is caused by the standing water in the discharge hose, and thus, a centrifugal pump will simply cavitate and do nothing but make some neat little bubbles in the bilge.

For boats stored in-water during cold weather the water in the bilge hose above bilge level can freeze when the bilge water is not frozen. This present an impossible situation to pump into.

Fill a grain silo with corn and then try to push a door open into it...... Pretty tough. The check valve creates the same type of resistance to the bilge pump, Centrifugal pumps deal horribly with any added head pressure..

Check valves on rotary vane pumps or diaphragm pumps do not suffer the issues they do on centrifugal Rule style pumps. I have seen everything from ruined interior cabinetry, cabin soles and engines due to stuck check valves. I have also seen boats that sank because of a stuck check valve..

The largest maker of centrifugal bilge pumps, Rule, specifically recommends not to use them.

They can be a danger if used on a system with centrifugal bilge pump. Bilge pumps are safety items anything that can prevent the pump from pumping becomes a potential danger.

Rule Pump Instructions
 
#6 ·
These valves quite often stick shut especially if the bilge pump does not cycle often. The biggest draw back is the added head pressure that the pump can not overcome. This additional head is caused by the standing water in the discharge hose, and thus, a centrifugal pump will simply cavitate and do nothing but make some neat little bubbles in the bilge.

For boats stored in-water during cold weather the water in the bilge hose above bilge level can freeze when the bilge water is not frozen. This present an impossible situation to pump into.

Fill a grain silo with corn and then try to push a door open into it...... Pretty tough. The check valve creates the same type of resistance to the bilge pump, Centrifugal pumps deal horribly with any added head pressure..

Check valves on rotary vane pumps or diaphragm pumps do not suffer the issues they do on centrifugal Rule style pumps. I have seen everything from ruined interior cabinetry, cabin soles and engines due to stuck check valves. I have also seen boats that sank because of a stuck check valve..

The largest maker of centrifugal bilge pumps, Rule, specifically recommends not to use them.

They can be a danger if used on a system with centrifugal bilge pump. Bilge pumps are safety items anything that can prevent the pump from pumping becomes a potential danger.
Maine, there are instances where you might need to install a check valve (I needed to) and ways to do so that doesn't give rise to the "standing water in the discharge hose" you mention (install it high up near the discharge point - not in the bilge with the pump itself).. I guess exactly what you do depends on the specific circumstances and the type of boat.

I've known check valves to fail open (bits of rubbish preventing the flap closing), but I've never heard of one sticking closed.. but then we don't get the freezing weather you get. I've known of boats that sank because there was no check valve fitted when they needed one..

IMHO, the bottom line is: Don't install a check valve unless your particular installation means you have no other alternative.

BTW, the other thing that can prevent the pump pumping is lack of a strum box.. make sure you use one. :)
 
#17 ·
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...
 
#16 ·
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 ?
 
#18 ·
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..
 
#21 ·
Lots of information here. The factory manual bilge exits out the stern. I installed the automatic electric bilge and placed the discharge high in the cockpit so I could see if there was a problem causing the pump to run. If water gets in the discharge hose I have much bigger issues. I test it occasionally to insure it works properly. During a test is when I discovered that the check valve was malfunctioning.
 
#27 ·
I work with centrifugal pump design every day. What's missing here is our basic tool, the pump curve supplied by the manufacturer. A centrifugal pump always runs on the pump curve, for every head condition along the curve there is a corresponding flow rate. The left end of the curve is the maximum head at zero flow, called shutoff. If you look at a pump curve you'll gain a whole new appreciation for the difficulty in applying centrifugal pumps.

You can learn a whole lot about your bilge pump by putting an open hose on it and running it in a shallow pan. Start with the open end down low and watch how much flow you get. Slowly raise the open end and watch how fast the flow rate falls off. At the height water stops coming out of the hose you have reached shutoff head. Measure the flow into a bucket and draw the curve for the pump. Some pumps have relatively flat curves downward to the right. A small amount of additional head pushes the pump back on the curve to the left and flow falls off very quickly. I attached a pump curve just to show what they include, curves for different impellors, efficiency points, horsepower curves etc.

I see here talk about having a loop well above the heeled water line. The fact is you want the loop as little above the waterline as will gaurantee you won't back flood when heeled. Any more greatly reduces the flow that you can actually pump. You might notice they rate bilge pump flow at about 2 feet of head. Lifting water 3 feet can cut the flow in half or more, and you might not get any flow at 4 feet!

There is also talk about venting the loop, to prevent a back siphon. This is true, however a forward siphon from a loop well above the water line to a discharge point above the water line actually will increase the pump flow a lot. So a tall vented loop can defeat your pump as well. When you do the test above trying raising the middle of the hose way up in the air with the open end near the ground. You'll see that the pump will move a lot of water way up high as long as the siphon on the downhill side pulls the water along. Drill a tiny hole in the top of that loop and the flow will fall way off.

A really important point missed here is discharge hose size on the pump. When you have only 2 feet of head to work with you really must avoid any friction losses. So jumping a 3/4" pump discharge up to 1" or even 1-1/4" can make a big difference, especially if it must run more than a couple of feet.

The comment about a small hole in the hose right at the pump discharge is a good one. In the instructions no one reads for commercial submersible pumps there is always a statement about drilling a 1/8" hole to prevent air locking. A bubble of air forms in the pump housing and the impeller can't grab enough water to build pressure enough to push water up the pipe. In a 44 story building in Manhattan I had to pull two pumps out of 18 foot deep tanks to drill the two holes that no one thought was important because those pumps air locked all the time!
 

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#28 ·
Also the voltage makes another HUGE dent in performance of these pumps. Suffice it to say that a Rule 2000 when installed in a sailboat may not even pump 25% of its face value rating... Many of these pumps are rated at "open bucket" (which means NO HEAD) and at charging voltages... Often times the little diaphragm pump with the $hitty GPH rating will outperform the centrifugal pump when "installed"...
 
#34 ·
Also just came across this from Rule:

"The Rule Pumps FAQs.

Can I install a check valve on the pump discharge?

Check valves are not recommended

Why doesn't Rule Pumps want check valve on the pump's discharge?
Check valves are prohibited by the American Boat & Yacht Council for use as an anti-siphon device-and with good reason: They're notorious for failing in both the open and the closed position, which respectively leads to flooding or failure to pump. If the valve is close to the pump, the pump may not be able to overcome the weight of the water on the other side of the valve, rendering the pump ineffective

Why does my automatic Rule Pumps turns off if I install a check valve on the discharge of the pump?
The automatic bilge pump turns on about every two and a half minutes to "check" for high water. If water causes resistance on the pump, it continues to pump until the resistance lowers. With the check valve installed at the pump, it cant feel the weight of the water, and shuts off, allowing the bilge to fill with water!"

They must have read my mind....;);)
 
#36 ·
I wouldn't use a check valve on an automatic centrifugal pump where's there's not problem to solve. A problem would be that you have such a long discharge hose that when the pump stops the hose water drains back causing the pump to cycle again. The risk you have with an automatic pump is if the valve sticks when you're gone your pump is OOC until you get there and fix it. Over time that may burn out the pump.
I do use a large bronze foot valve on my large manual diaphragm pump which reaches down into a bilge pocket that's about 2 feet below the waterline. This has a large hose and I'm pumping a lot of air to get to the water. The biggest risk is of it being stuck closed in an emergency so I have to flush it periodically. I can pull the hose and bang on it if it's stuck.
 
#37 ·
Been reading lot of posts on this subject. Just put in a West Marine centrifugal pump with electronic float switch. I know I won't put in a check valve after reading. The deep section of the bilge is around 30" deep then starts to the stern rising another 8-10" guessing. Originally had a diaphragm pump that gave up the ghost. It was mounted toward the back of stern. Where the hose met there and then went to the discharge it went up about 2' under the cockpit seats and over to the back and then down to the discharge. The drain discharges under the stern. Sits about 6" off the water line. Have the issue off backflow so it won't turn itself off. Replaced the hoses. Using 5/8. What I have not seen is where best places are to make a loop and how much is really needed. Wondering if I could find a spot behind the engine area and make a shorter loop. Does it need to be a vented loop or just loop the hose up. Also intend to put a large high volume above it when I get this one corrected. Is it better to have the discharge straight out the back of the stern vs underneath

Thanks
Bruce
 
#38 ·
It needs to be a vented loop with the vent as high above the water line when heeled as you can get.

Some people use a big centrifugal pump with inlet a few inches from bottom of bilge. Then a small diaphragm pump with the intake at bottom of bilge. The diaphragm pump has an integral non-return valve. But still the hose should have a vented loop although the hose can be smaller than the big pump hose.
 
#42 ·
First and foremost as a land pump person my electric pumps are there for a convince :)

That being said I have a high pump and a low pump in a small deep section of the Cal 29 bilge

Both pumps have siphon breaks well above the waterline (rub rail) height and the deep pump has the jabsco check valve which is needed due to the tiny capacity of the deep section

The valve works fine

Of course I also have to manual pumps BUT there also only going to cover minor things as unless you have seen water with a small amount of head pressure geyser out off a 2" hole you have no idea how fast things flood :)
 
#44 ·
captain jack,
The way i see it, if you take on some water and settle down in the
stern a little your drain well will help you for a little while...but then if you settle further,
with your bilge pump emptying in the boat rather then outside...well not a good
situation. ...Thinking Titanic.
Maybe set up ok to pump out rain water, with a 2nd bilge pump exiting transom.
 
#47 ·
that is thinking 'titanic'. the drain is around 6" to 8" above the water. if i take on enough water to make the boat sit that low, my bilge pump, although the one recommened for my size boat, will never be up to the task of saving the day.

i suppose, thinking with such an ultimate calamity in mind, if i decide to blue water sail my 27' cal, i will need to think about getting a much larger bilge pump and route it out through the transom.

here, in the bay, i can't think of anything that would let that much water fill my bilge short of a hull breech. my bilge pump will most definately not keep her afloat in that sort of situation...regardless of how i route the hose. i have to wonder how many non-blue water sailors' boats have bilge pumps that could deal with that kind of situation.
 
#45 ·
Cockpit drains can be plugged by debris (leaves, bugs, etc.). If that happens then you have to ask does the bilge pump system still work?

Most boats won't sink if the cockpit drain is plugged. The cockpit is usually designed so it will not hold that much water. But if the cockpit is also the bilge drain then probability of sinking goes up.
 
#46 ·
if this cockpit drain was like the ones on my holiday 20, i'd agree with that possibility. however, it's not. it is much larger in diameter. bugs would never be able to clog it...well, maybe prehistoric bugs or a few of those giant madagascar cockroaches washing down to the drain all at once. i am at the boat every week, often more than once, and am thinking about doing the live aboard thing. it would take a bit of seriously gross negligence for the drain to get clogged with anything. i have never measured the hole but i'm betting it's over and inch and it has no tunnel that could get clogged. it's just a hole in the bottom of the transom.

i suppose in some sort of case of extremely odd circumstance that might be a concern but, i really don't see that as being a likely event...not on this boat.
 
#51 ·
I have a check valve on my low capacity 'dry-bilge' pump and then none on the higher up, bigger capacity 'oh ****' pump.

If the low capacity pump jams im not that bothered - ill notice at some point and fix it. I want the 'oh ****' pump to be worked at all times though (its wired direct to the battery, while the little lower one is wired to a 3 way switch/breaker)
 
#52 ·
Sabreman - I am sailing a Sabre 38 Mk I and just ran into the problem that you discussed back in 2006. My bilge pump stopped working and after lots of fiddling around, including replacing the pump, I figured out that the check valve was the issue. The problem is that without a check valve, the very shallow bilge of the Sabre refills quickly from the reflow. The pump cycles continuously as it pumps water out, stops and then the bilge fills with the backflow from the hose, starting the pump again. If the check valve is a risk, how can this problem be fixed in a shallow bilge boat?

Thanks, Nomad Skipper

Sabre 38 #83 "Nomad"
 
#53 ·
Nomad, I had a similar situation on my slack bilged CS30 and after sorting all the things that let water into the Boat like stuffing box and Ice boxes draining into the bilge area (part of a list of PO setup bad ideas) I am to the point where the only water that gets in the Boat if from cleaning my knot meter, I temporarily close off the limber hole to keep it in that compartment and some sneaks in through the keel stepped mast and is unavoidable. To further complicate drying the bilge there are limber holes all over the stringer grid and its very difficult to get all the water no matter what the method.
Although I don't have the short cycle issue others do I don't want water down there all the time so I test the pumps regularly by introducing water using a garden hose normally and then shop vac it dry. I will be doing other things like experimenting with rising limber holes on various compartments.
On previous boats with enough bilge I would just wash everything down regularly to keep trash from washing into the pump sump, a 8-10" sump is all I want.
Everyone needs one of those shop vac 5 gallon bucket toppers from Home depot they are only $20 and you use the bucket for other things when its not a vacuum.
 
#54 ·
You need a loop in the hose above the water line with a vacuum breaker valve on top of the loop. Don't make the loop too high as the vacuum breaker prevents siphoning out, which helps the pump flow. With a vacuum breaker in the line the pump has to lift the water to the top of the loop. Make the hose larger while you are at it. You now have a longer hose and you don't want any friction loss on a pump that can't produce very much flow against any kind of head, friction or height.
 
#55 ·
Gary, the problem there is that when the pump shuts off the water still in the longer bigger hose runs back and the pump starts up again.My solution was adding a small pump and small hose to the system. Triggered by a time delay switch from auto head light delay. It got its power from the hot side of the float switch and trigger from the other side.After the big pump shut down it ran for(adjustable )up to 3 minutes and slurped up the dregs Also used same idea in the head to run the vent fan .(needed after I'd left the room)
 
#56 · (Edited)
Gary, the problem there is that when the pump shuts off the water still in the longer bigger hose runs back and the pump starts up again.
I agree.. My discharge hose is about 30 feet long.. Lots of water in that hose. The loop does not work because the loop is at the end of the hose. Absolutely useless for the back flow problem. Fortunately Rule has a pump that is design with a tricuspid valve for bilge pump applications.. ..specifically for this back flow problem.. It is the Lopro 900..

It is the only centrifugal pump that really works in my boat. The big problem with centrifugal pumps with or without one way valves at the outlet is mostly that the pump chamber gets air in it after emptying the bilge. The one way valve does not let the air out, so the pump cavitates next time it turns on.

So the pump must be designed to let this air out. This problem plagued me in my fridge pumps, air conditioning pumps and shower pumps until I realized what was happening.
Bryce
 
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