Check valve ghost

[Skipper]

I have a sump behind the keel, which acts as the bottom of the bilge. The bilge pump therefore pushes the water up through the hose to the engine compartment, then out the transom. There's a bronze check valve to keep the water from flowing back into the sump.

Well, the check valve doesn't work. It acted up a couple years ago, and I found a piece of wood in it. Was fine for awhile after, but now it's back to the old ways. I took it of the line and found nothing inside, and the flapper bangs back and forth like a bell clanger. Looks fabulous. And is connected in the correct direction.

Here's what happens: I pump the bilge till the float switch kicks it off. Then water slowly seeps back in for about 15 seconds. Then, something lets loose, and all the remaining water in the line rushes back into the sump, re-activating the float switch. It's an idiotic cycle.

Any ideas?

 

[Stu Jackson]

Buy a new check valve. They wear out and fail.

 

[JK_Boston_Catalina310]

This subject came up a couple of months back. Search on bilge pumps and you should find that previous discussion.

The bottom line of that previous discussion was that while check valves are used and recommended quite a bit on submersible, centrifugal pump (that is the type of pump that most have for electric bilge pumps, like Rules) in other applications (I use them all time in groundwater treatment systems and construction dewatering systems) there are some significant problems with the application on boats. First, the typical Rule bilge pumps appear to have exaggerated pump curves that don't take into account the charge state of the batteries. Second, check valves are very rarely maintained appropriately on boats. (I take mine apart, clean and grease it once a month, this is a practice I picked up from use in industrial applications. However, most don't even do this once a season.) Based on these issues, MaineSail and others have recommended not using check valves as a stuck one can sink a boat. Just something to consider.

Fair winds,

Jesse

 

[capta]

As you have found out, check valves can fail. I would recommend a big loop in the exhaust hose with a vented loop at the top. Most people try to get the top of the loop to just under the deck, leaving enough room to maintain it.
If I remember right, Rule recommends not using a check valve with their pumps, or at least they used to. Check the installation instructions.

 

[Skipper]

Thank you.

If I remove the check valve, and\or install a vented loop, the same problem will exist: water in the line gravitating back into the bilge once the pump stops.

There is very little danger of seawater coming in through the output. It's a 1 1\2 feet above the waterline on the transom. Water intrusion is not my concern with this system, given the boat's current application. In the future, even if water came in during heavy weather sailing, the pump would just spit it back out. However, removing the check valve removes a layer of safety.

I can do plumbing. However, persistent leaks and strange activity are not my strong point. Would greasing the check valve flapper improve things? I would hate to install a new part, only to experience the same problem.

Another thing: The check valve flapper is totally unrestricted in movement. Therefore, any tilt downward allows the flap to open. If there is no water pressure, it seems that the flapper would creep open(?). The check valve is pointed up slightly, so I'm guessing this would not happen, but I'm wondering if there is any adjustment that can be made - there is a tiny bolthead on the exterior, which I don't know what it's for.

 

[Maine Sail]

"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!"

 

[Skipper]

Thanks, Mainsail. But those instructions appear to be for a water sensing pump, not a pump with a float switch. And my check valve is not close to the pump, it's 5 feet away in the engine compartment. I have no pumping issues or safety issues.

Also, again, removing the check valve would not solve the problem: Water in the line gravitating back into the bilge once the pump stops, which causes the pump to cycle again. It cycles about 3 times a minute due to this issue.

 

[Maine Sail]

Thanks, Mainsail. But those instructions appear to be for a water sensing pump, not a pump with a float switch. And my check valve is not close to the pump, it's 5 feet away in the engine compartment. I have no pumping issues or safety issues.

Also, again, removing the check valve would not solve the problem: Water in the line gravitating back into the bilge once the pump stops, which causes the pump to cycle again. It cycles about 3 times a minute due to this issue.

Skipper,

The sheer FACT is that Rule does not recommend any check valve on any of their centrifugal pumps. This is not disputable. You can do what you want on your boat but you would be ignoring the advice of the manufacturer of the pump, and creating a potential safety issue.

This is widely known and can be very easily be confirmed with a quick call to Rule. They will and can send you the info on why NOT to use a check valve on any of their centrifugal pumps. Course they will tell you this right over the phone too. No check valves on ANY Rule centrifugal pumps.

This does not just apply to their automatic pumps but ALL their centrifugal pumps. Just because DIY's and builders do it to save money, does not make it a correct or safe installation.

The prudent installation on a sailboat where you want to prevent flow-back is either to install a diaphragm pump, the ideal solution, or to get a float switch with a delay. The delay will not always solve the problem however so a diaphragm pump that can handle a check valve, or has the check valve feature built in, is the proper & safe solution.

A check valve in a centrifugal pump is not a solution, it is a potentially dangerous installation.

So, if you want to solve the problem the right way then you'll want to install a diaphragm pump. If you want to go against the sage advice of the manufacturer buy another check valve....


Other than what I posted above.. Here is one of the responses Rule sends out when you ask this question:

Both Rule and our competitors' centrifugal style bilge pumps have very little air vacuum pressure because there is a large gap between the centrifugal impeller and the impeller housing (depending on the pump, it could range between 1/16"-3/16") which allows high flow and some bilge debris to flow past the impeller without damaging the unit.

The negative side of the having the large gap between the housing and the impeller is the impeller needs to come in contact with water to pull the water out of the bilge (water being a lot thicker than air).

A check valve in the bilge hose seals air in the hose and will not allow the water to come in contact with the impeller. The pump may be in a few inches of water (or completely submerged) but because of the air pocket, the pump cannot remove the water from the bilge.

If you wanted to remove as much water as possible, you could try installing a diaphragm style pump. The diaphragm pumps have internal check valves and are self priming to at least 6'. The only drawback is that the diaphragm pumps do not have as much flow as the centrifugal pumps. If you mounted the centrifugal pump switch higher than the switch for the diaphragm pump, the diaphragm pump could be used for the daily water seepage and the centrifugal pump could be used for emergency pumping.

 

[Scott T-Bird]

Skipper, I think you have a problem with the location or function of your float switch. Also, why should you rely on the float switch to pump out the bilge? You should solve the leaking and worry secondarily about the float switch. I think the problem is that you want to rely on a check valve, when a check valve shouldn't even be part of the equipment.

The line should not carry enough water so that when it empties after a pump cycle it raises the water level to the point where your float switch is triggered "ON". You should possibly get a float switch that operates properly so it is not activated at low water levels.

With mine, http://www.jamestowndistributors.com/userportal/product.do?part=117556&SHOPZILLA&CA_6C15C=613373747 there is obviously backwash with an anti-siphon loop, but the float switch keeps the pump on long enough to draw the water down low enough so that it isn't activated after the backwash ... the water would have to rise another couple of inches in the bilge for it to be triggered on again. For some reason, you may have too much volume in your line or the switch isn't designed properly (switching on and off at the exact same level). A switch that works properly keeps the pump on long enough to draw the water a few inches lower than where the switch triggers on.

Besides that, I keep the bilge dry so the float switch never has to be relied upon except for emergency, which shouldn't ever happen. Why not pump it down manually if you have a smallish leak problem? You are surely at the boat often enough to prevent the water level from rising to the point where the float switch is activated, no? If it rises enough in just a few days that your float switch activates, you have a problem that should be solved and it has nothing to do with the bilge pump.

 

[Steve Dion]

I guess my take on this would be if the valve can stick in the open position it can also stick in the closed position (probably when you need it the most).

It seems to me if you can find a high spot in the boat to run the discharge line to you would not need to worry about back flow and there would not be a check valve to worry about.

 

[heritage]

You should remove the check valve. Another solution to getting a somewhat drier bildge, other than installing a displacement pump, is to install a small and inexpensive centrifugal pump with a small diameter and short as possible discharge hose. You need to put it below the float switch of your main pump. Less water will flow back in the bilge and you have a backup pump.

 

[Skipper]

Thanks all.

The bilge pump is at the exact bottom of the bilge. There's no way to change the characteristics of the bilge. It's a sump. Deep. Bristol owners will know it.

Bristol installed the sump (bilge) pump and check valve. It's original equipment. There has to be a check valve. Otherwise, the water in the portion of the line lower than the top loop will rush back into the sump, which it's doing now due to (apparently) a failed check valve.

There is no way to keep the sump completely dry. The shaft packing flow ends up there, and the ice box drains into it. There is always a half inch of water in there. There is no place for another, smaller pump at the bottom. There's already the sump pump at the bottom. There's nothing wrong with the float switch. I'm not going to manually pump it out - the ship's manual pump hose is at the same level anyway, and would do nothing. It's a deep sump, partially covered by a glassed-in shower sump. Manually pumping it with a portable is a PITA, with the discharge pointing out into the cockpit. Takes 3 hands. I'd have to do this multiple times a weekend if that were my process, and why would I if the original system that was designed and installed to prevent this is working properly?

It has worked well for 29 years. The check valve is well away from the pump, near the top loop. No air issues, no pumping issues, nothing that needs any attention, until recently.

The question was never whether or not the check valve should be there. The question was why is it no longer performing. Someone said maybe to grease the interior, another said just get a new one. I'll try those remedies in that order.

Thanks again.

 

[Skipper]

By the way, I never said the bilge pump is a Rule product. I forgot the mfg, but it's not Rule.

 

[Maine Sail]

Thanks all.

The bilge pump is at the exact bottom of the bilge. There's no way to change the characteristics of the bilge. It's a sump. Deep. Bristol owners will know it.

Bristol installed the sump (bilge) pump and check valve. It's original equipment. There has to be a check valve. Otherwise, the water in the portion of the line lower than the top loop will rush back into the sump, which it's doing now due to (apparently) a failed check valve.

There is no way to keep the sump completely dry. The shaft packing flow ends up there, and the ice box drains into it. There is always a half inch of water in there. There is no place for another, smaller pump at the bottom. There's already the sump pump at the bottom. There's nothing wrong with the float switch.

It has worked well for 29 years. The check valve is well away from the pump, near the top loop. No air issues, no pumping issues, nothing that needs any attention, until recently.

The question was never whether or not the check valve should be there. The question was why is it no longer performing. Someone said maybe to grease the interior, another said just get a new one. I'll try those remedies in that order.

Thanks again.

Form what you are saying that statement is confusing and makes little sense in the realm of the discussion of back flow.. If the check valve is "near the top loop" then what is in the hose on the bilge side will eventually drain back anyway and you are only talking about a 1' or so of water in what is likely a 3/4" hose that is making this difference???

Replace the check valve if you want, as they are not very reliable on a bilge system anyway. They are also quite in-expensive.

Check valves on centrifugal pumps are perhaps my number one cause of killed/destroyed battery banks. Failed or stuck float switches are probably #2 and parasitic loads & battery switches left on #3....

With a leaking stuffing box you could not pay me to install a check valve on our boat, but as Stu always says "your boat your choice".

All we can do is try to give you the accurate information direct from the manufacturer of the pump. Just because Bristol ignored proper installation practices does not mean it should or has to stay that way. Many builders have chosen to ignore proper installation procedures of centrifugal pumps in order to save a buck..

Cape Dory has a similar sump on many of their boats and they used a diaphragm pump to solve the problem. Our CS also shipped with a diaphragm pump. Different builders try to save money in different ways, and a diaphragm pump is more costly.

If you must install a check valve I would advise a small hole in the bottom of the hose right before the check valve and the check valve located closer to the pump.. This will allow the pump to purge the air and make the check valve more reliable and less prone to causing the pump to cavitate, fail to evacuate the bilge water and kill the battery bank... They have a very nasty habit of sticking closed and also draining back, as you've found... This hole in the hose is a Band-Aid to a Band-Aid however.....

Even as a kid working in boat yards customers would come in with dead batteries and we'd charge them up only to find the bilge pump stuck on because the check valve was stuck closed. Many a cabin sole or worse was ruined and many battery banks were not salvageable.

The owner of the yard would gruffly say "Kid go yank that god damn check valve and send them on their way." This is a guy who never even set foot on the boat but could diagnose it from a mile away. Never once did I go down to the boat and not find a check valve causing the issue.. On occasion they would have to swap out the pump for a diaphragm, due to back flow, but in most situations the back flow would not cause cycling. Back then the float switches had mercury and were MUCH more reliable so it was almost always the check valve... This was in the early 80's...... The problem is not new......

 

[Don S/V ILLusion]

Thanks all.

The bilge pump is at the exact bottom of the bilge. There's no way to change the characteristics of the bilge. It's a sump. Deep. Bristol owners will know it.

Bristol installed the sump (bilge) pump and check valve. It's original equipment. There has to be a check valve. Otherwise, the water in the portion of the line lower than the top loop will rush back into the sump, which it's doing now due to (apparently) a failed check valve.

I wouldn't dismiss the suggestion other have made to eliminate the check value. That is good advice regardless of the other concerns you have. They fail, as you know, and can fail to block flow in both directions which could be disastrous. They are other ways to cure your problem.

I am familiar with your bilge configuration and can assure you many boats, including mine, have even deeper ones.

Trash the check valve and place a loop as close to the sump as practicable.

As you pointed out, you already have other sources of water constantly feeding the bilge so it will never be dry anyway. Why create a potential problem (check value) for no purpose?

.[/quote]

 

[Skipper]

As you pointed out, you already have other sources of water constantly feeding the bilge so it will never be dry anyway. Why create a potential problem (check value) for no purpose?

.

[/quote]

The check valve keeps the pump from incessantly cycling 3 times a minute. Again, water intrusion is not the issue, so a higher loop would do nothing to stop the described problem.

 

[Maine Sail]

By the way, I never said the bilge pump is a Rule product. I forgot the mfg, but it's not Rule.

Does not really matter what brand. If it is a centrifugal style pump it should not have a check valve.

 

[kloudie1]

Not campaigning for or against check valves.. My Hunter 34 came originally with one less than a foot away from the bilge pump. The bilge is shallow and far away from the outlet, which is just below deck level. There is about 12 feet of hose between the check and the outlet. The volume of liquid in the hose is a little more than the amount of liquid to fill the bilge to the place where the switch turns the pump back on. When the check leaks, the pump cycles..
Experience: There has been one failure of the PVC in-line check since 1985. That failure was a small piece of 12 Ga. wire insulation that a careless electrician (me) let fall into the bilge. The valve happened to close on the 1/8" long tube of insulation, and it stuck on the seat. As a result, the pump cycled about every 4-5 minutes for a few days.. I was able to pull the valve and clean it and the 28 year old valve is fine again. I am on shore power, so the cycling did not kill the batteries. I purchased a new identical PVC check as a spare and carry it aboard. I have learned to clean the bilge and not let stuff that falls into it stay there. I think the fact that the dehumidifier (runs year round when boat is not sailing) drains into the bilge and causes the system to cycle keeps things working. I have considered flex impeller and diaphragm pumps to eliminate the check, but I wonder if that same piece of insulation would have failed the check valves in a diaphragm and caused it to run continuously..??
My buddy's Tartan 37 had a rubber vane impeller type bilge pump that worked fine with the long discharge hose.. No check needed, but it ate MUCH more power when running than a diaphragm or centrifugal.

 

[Skipper]

Form what you are saying that statement is confusing and makes little sense in the realm of the discussion of back flow.. If the check valve is "near the top loop" then what is in the hose on the bilge side will eventually drain back anyway and you are only talking about a 1' or so of water in what is likely a 3/4" hose that is making this difference???

Yes. The bottom of the sump is about 10" x 4". Easy to fill. It has not drained back for many years; the water held back by the check valve in a vacuum. Your recommendation for a diaphragm pump does seem more stable, though.

[/quote]With a leaking stuffing box you could not pay me to install a check valve on our boat, but as Stu always says "your boat your choice". [/quote]

The system is used consistently, so it has always been clear. But, yes it does seem worrying that if that flapper failed closed, it could be a huge problem. Thank you.

 

[Maine Sail]

The system is used consistently, so it has always been clear. But, yes it does seem worrying that if that flapper failed closed, it could be a huge problem.

With a clean bilge and the physical location of your check then you may not have issues with an n=1 scenario. Problem for me is that I see way more than n=1 so I tend to see the very high failure rates of check valves and pumps failing to pump because of check valves when compared to single boat owner.. Also not all systems will hold a vacuum on the hose with the check in that location. Sounds like yours has.. When you have only a single point of data, n=1, that is working, it is very often tough to grasp why it may not be the absolute best choice....

Thank you.

Always glad when or if I can help.