Bilge pump check valve

[Jeff and Sarah]

I've never been a fan of check valves in line with a bilge pump but I have to confess that I have one. I hate it, but it seems like a better alternative to a couple gallons of water backwashing into the bilge every time the pump shuts off. I put the check valve in because I used to collect a fair amount of water in the bilge from various areas and the bilge pump had to run from time to time. I hated the idea that the pump would eat up some battery power when it ran just to have some amount of water rushing right back in.
I've solved the water intrusion issues and now have a very dry bilge. The pump NEVER runs so I check it often- every couple days I'd say. I also check the float and from time to time I dump some water down there to make sure the pump is working (not just making noise) and to ensure the check valve isn't stuck. Yesterday I found the valve stuck closed. I've got it sorted out for now, but what do most people do to not require the check valve? On my 33, the bilge through hull is painfully far from the pump- it's in the aft lazerette exiting through the stern shear. There is a lot of hose (and elevation) between the pump and the through hull. I can't seem to find a good way to locate the through hull much closer to the pump, so for now I live with the dreaded check valve. Please- someone swoop in with a great solution.

[Duncan]

I've never been a fan of check valves in line with a bilge pump but I have to confess that I have one. I hate it, but it seems like a better alternative to a couple gallons of water backwashing into the bilge every time the pump shuts off. I put the check valve in because I used to collect a fair amount of water in the bilge from various areas and the bilge pump had to run from time to time. I hated the idea that the pump would eat up some battery power when it ran just to have some amount of water rushing right back in...
...Yesterday I found the valve stuck closed. I've got it sorted out for now, but what do most people do to not require the check valve? On my 33, the bilge through hull is painfully far from the pump- it's in the aft lazerette exiting through the stern shear. There is a lot of hose (and elevation) between the pump and the through hull....
I can't seem to find a good way to locate the through hull much closer to the pump, so for now I live with the dreaded check valve. Please- someone swoop in with a great solution.

That was too tempting, particularly as I had just seen a discussion on this recently. The short answer is (from what I read, not my own experience) "use a diaphragm pump instead of the check valve, but keep your centrifugal pump for its higher capacity"

This is from Plastic Classic Forum

...diaphragm pump(emphasis added), which can suck the bilge dry, and doesn't need to live down there with the bilge water. The nice thing about it being able to suck is that it bring the water up and when it shuts off the water doesn't leak back down into the bilge, as it does with the centrifugal "pusher" pumps...You might also choose to have a larger centrifugal pump to move more water in an emergency, but for everyday bilge water removal, the diaphragm pumps are just about ideal.

As I'm sure you can see by Googling, there is a lot of discussion around "staging" of bilge pumps, which seems to boil down to two things:
a) Have a small pump to get 'nuisance' levels of water out of the bilge
b) Have a HUGE pump to try and stave off disaster if catastrophic amounts of water enter the boat. The reasons for saying HUGE are that
- gallons-per-hour ratings don't allow for the height that water must be lifted, and that
- gallons-per-hour from even a small hull breach can be astonishingly high. I once calculated the amount of water per hour that could come in from a 1" through-hull failure. I am sorry to say that I can't recall the figures or the method, but I do remember that it was a much higher amount than I would have guessed from the size of the hole.

[Matt Cawthorne]

Better stuck closed than open. I have had a flooding incident when on a reach and the check valve stuck open. If your through hull is under water and the valve is open the reverse siphon fills lots of water in the boat quickly. If your fuse burns out at the same time it gets very messy.

I moved the exit for the bilge pump well above the water towards the center of the transom. I added a flapper valve to the exit. I added a siphon break to the top of the loop and don't worry about the water from the line sloshing back into the bilge. It is a minor thing.

Matt

[Jim Walsh]

I also have a siphon break on both my bilge pumps, an electric centrifical and a manual diaphram. Both exit aft under the counter. I do not have check valves.

[Jeff and Sarah]

Well right now I don't necessarily agree that it's better to have it stuck closed than open because I'm about to be traveling for work for 2 months and the boat will just be sitting at the dock. I've looked in to the diaphragm pumps before and might just need to bight the bullet. I have been considering adding a much smaller rule pump to handle the normal stuff and promote my larger pump to 'emergency only' duty. I suppose I can tackle both things at the same time. The boat doesn't take on any water though so it's low on the priority list right now (since the large pump isn't drawing anything from the battery bank).

[Maine Sail]

Jeff,

Lose the check valve and just deal with the hose drain another way. Check valves are a major safety hazard on centrifugal pumps. These pumps already lose almost 50% of their stated capacity when properly installed. Now add corrugated hose, twists & bends and a check valve and your often down to probably 1/3 of rated capacity or less. Centrifugal pumps often can't even overcome the standing water in the hose above the check valve...

ALL bilge pump discharge hoses should have a siphon break and a high loop if the outlet can EVER dip below the water for any reason. A high loop only will not always stop a siphon so a working siphon break is a really good thing to have. The ABYC specifically stipulates that check valves may not be used in place of a high loop or siphon break to prevent back siphoning.

I can't even count the number of check valves I threw into the dumpster when I worked in boat yards.

Please keep in mind that Rule does not even make a check valve intended for use with centrifugal pumps. All their check valves are designed to be installed on the suction side of a pump to keep a prime not on the discharge as many boaters often mistake them for.

There have been many a sunk boat because the centrifugal pump just could not overcome the head pressure to open the check valve. Also keep in mind that just because it opens when your watching it and your batteries are fully charged doe NOT mean it will open if your boat develops a leaking stuffing box or seacock and the battery begins to get low. The head pressure of centrifugal pumps is directly related to voltage.

A check valve on a centrifugal pump is the worst idea since a boat made from window screen....

[Maine Sail]

Better stuck closed than open. I have had a flooding incident when on a reach and the check valve stuck open. If your through hull is under water and the valve is open the reverse siphon fills lots of water in the boat quickly. If your fuse burns out at the same time it gets very messy.

I moved the exit for the bilge pump well above the water towards the center of the transom. I added a flapper valve to the exit. I added a siphon break to the top of the loop and don't worry about the water from the line sloshing back into the bilge. It is a minor thing.

Matt

Matt,

Your reasoning is odd and all in relation to an improperly installed bilge pump. A stuck closed check valve or a pump that can't open it has sunk many a boat. ABYC also specifically advises against the use of check valves in place of a proper high loop.

Your pump was installed incorrectly and you were wrongly depending upon a check valve to keep your boat from sinking. You did the right thing by fixing it..

[Jeff and Sarah]

I'll ditch the valve, but I'm still trying to come up with a new solution. I guess the diaphragm pump will be the way to go. Surely I'm not the only CD owner with this problem.

[Sea Hunt]

In the October 2010 issue of SAIL there is an educational article with diagrams and pictures entitled "Optimizing Bilge Pumps". It is found at pages 102-107 and is authored by Adam Cort. As I know very little about the subject matter I found the article informative and educational. It discusses the installation of primary and backup bilge pumps, plumbing, wiring, etc.

In the January 2011 issue of Cruising World there is an article about check valves entitled "Get To Know Your Check Valves". It is found at page 79 and is authored by Steve D'Antonio. From my reading of the article Mr. D'Antonio appears to recommend against check valves in the bilge area. He also states that the American Boat & Yacht Council ("ABYC") prohibits the use of check valves "to prevent downflooding" because they can malfunction. Mr. D'Antonio suggests the use of an anti-siphon valve to prevent backflow.

[Jeff and Sarah]

I'll look up those articles. To be clear though, my back flow is NOT caused by taking water from outside the boat so I don't see how an anti-siphon valve will help. Obviously they are beneficial, but they won't affect the issue I'm tackling. I'm talking about the back flow caused by water in the bilge pump's hose that didn't get fully pumped overboard. This water stays in the hose due to the hose length and the elevation it must traverse. I'm thinking that the problem is caused by the diameter of the hose- I think it's 1 1/4, though I can't recall for certain. Anyway, if I reduced the size of the hose, while it would restrict flow somewhat, it should also reduce the volume of water left in the hose after the pump shuts off. This whole issue is more academic than anything because the bilge stays dry- but I do know the back flow would occur if the bilge started collecting water so I'm trying to stay ahead of the problem.

[Dean Abramson]

Jeff and Sarah,

I had the exact same problem on our 25D: long outlet hose, pump runs, float switch drops, pump stops, water flows back downhill out of all that hose, pump comes on again, cycle repeats itself... I came to my boat one day, and the battery which fed the pump was totally dead. (And of course, the bilge had water in it.) After that, I quit using the Auto mode entirely.

I may remove the check valve in my current electric pump's outlet hose, because they are not a great idea for all of the reasons mentioned above. And then, again, just quit using the Auto mode.

On the 25D, I took the attitude that it was my job to make sure my boat had no leaks. If it DID develop a leak, the pump was only going to pump until the battery died anyway. With a slow leak, hopefully you will revisit the boat before it is an issue. If it is a big leak, then probably the pump will work for a couple of days (I am guessing here) and then quit. If you are at a dock, someone might notice the pump going a lot, or the boat slipping downward, and call you. But if you are on a mooring, like I am, the boat will probably just sink at some point after the battery dies. (I am just trying to cheer you up here.)

I am contemplating keeping the check valve in my current setup, but adding another electric pump, higher up, which does not have a check valve. The lower one will remain for workaday use, and the upper one is for emergency use. If all is well, the upper one will never have water in its outlet hose which can then run down into the bilge. But if you do use the higher pump, it just needs to be higher than the point in the bilge which represents the water height of both of the hoses having drained themselves.

I am wondering, folks: if I install this upper pump, is there any downside to having it tee into the outlet hose of the lower pump? I guess what I am asking is whether in an emergency, that single hose could handle the output of both pumps running simultaneously, without restricting the flow. My brain cannot quite get around that part. My guess is that it depends upon the diameter of the hose. (No, I cannot tell you from here what size my hose is, or what the outputs of the pumps--current and envisioned-- are.) If the bottom pump died, the water from the upper would not be able to go thru the tee and head down to the bilge, because of that rascal check valve.

I am thinking that this upper pump would be in something like a plastic milk crate, and would hang in the bilge, about halfway down. The fitting to the outlet hose would be something that is easily detachable, so if you want to get at something below, you can haul up the basket, undo the hose, and get the pump out of the way. Similarly, the wiring would also need a user-friendly connector, or excess length.

Anyone want to point out flaws in this scheme? By the way, we also have a regular hand-operated bilge pump installed in the cockpit, of course. And we carry a Thirsty Mate, which we use mainly to pump out the dinghy, but is available for more dramatic tasks.

Jeff and Sarah, good luck. Let us know what you do.

Good luck,

Dean

[Matt Cawthorne]

Main Sail,
Perhaps my sarcasm was lost in my wording. It might have been clearer to say something like 'the only thing worse than no bilge pump is one that relies on a check valve' I believe that the installation in my boat was original and that many Cape Dories have the same fault. The exhaust of the bilge pump on my CD was above the water on an even keel, but not when heeled over by 20 degrees. I have noticed the same on at least a few other CDs. It should never have been placed there. It is not pretty to have the bilge pump exhausting high above the water line, but it is safer even if there is more volume loss. A high vented loop is a good idea, but it is not enough. Vents can become clogged over time. I have added 3 features to improve the reliability.
Firstly I have plugged and glassed over the original through hull and moved it higher, on the transom and on the opposite side from the vented loop. Why the opposite side? Because if the outlet and the loop are on the same side of the boat, it becomes impossible to achieve the 'high' in terms of a vented loop. The heeling moves the vented loop much lower. If they are on opposite sides the loop is high when the outlet is lower and when the outlet is high above the water the vented loop is not needed.
Yes, I replaced the original check valve with a whistling, vented loop. More precisely a moaning, vented loop. The check valve makes a groan whenever it breaks the siphon. This way there is a constant check on it's ability to act as a siphon break.
Lastly, there is now a flapper valve on the exhaust of the bilge pump. It is a check valve of sorts, but it is only there for high, following waves.

In addition to those things the original Rule 1000 pump and 1 inch diameter lines have been replaced with a 3600 and larger diameter lines. The float switch is replaced with a pressure activated switch and a second pressure activated alarm switch is added. Oh yeah, the boat is equipped with a manual pump and there are 3 good sized buckets on board. I am a believer that there is no better pump than a scared man with a bucket. On top of that, all through hulls are closed when the boat is unattended, with the exception of the cockpit scuppers. While I have replaced all the rubber hoses on the boat once, this thread is a good reminder that it might be a good time to replace the cockpit scupper hoses again.

Matt

[rtbates]

went through the same thing years back. MY answer was to toss the drop-in pump in favor of a jabsco diagraphm pump mounted high in the cockpit locker. It's about half way between the bilge and the stern outlet. I use a strum box with a built in one way valve. This keeps the water between the pump and the bilge from returning on pump shutoff. The pump itself keeps any water that enters the stern outlet from getting past and into the bilge.. My senor is a "Smart switch".

I gave up on drop in pumps with float switches after the umpteenth time I had to remove hair from the impeller to make it work or shake the float switch to get it to work..

[Tom Keevil]

I notice that the diaphragm pumps are marketed for use as either a bilge pump or a deck washdown pump. Could you buy one pump, install a Y-valve and use it for both?

[Dean Abramson]

Tom,

I like this idea, since I have been exploring the idea of installing a washdown pump also.

The obvious drawback I see at a glance, unless I am missing something, is that a $200 washdown pump will pump only about 300 gal/hr., while a $200 submersible bilge pump will pump 10 times that much. Not really familiar with them, it seems to me that maybe a lot of the washdown pump's mission is to develop pressure, not so much pump volume. ??

If you go down this road, please update us on what you are learning/doing. I am intrigued.

Dean