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Old 26-03-2019, 08:39   #1
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Question Check valve for bilge pumps?

Our catamaran has 4 electric bilge pumps, one for each hull and one for each engine room. The bilge pumps are vane models, as usual.

Since the outlets are below the bridgedeck waves will fill the hoses.
In case of the engine bilge pumps, there is no check valve between outlet and the bilge pumps. So the engine bilges slowly fill with seawater.
The hull bilge pumps have a flap-type check valve. These leak, so the seawater in the hoses will also leak into the bilges. This is a problem, I do not like to dry it all the time and it removes the labels from the beer and wine bottles.



I have tried to find suitable 1" check valves, and did not succeed. I hope one of you has a suggestion.
I tried the Jabsco check valve. These leak already when new.
I tried the Whale joker-type check valve. These also already leaked when new.
I tried the Trudesign check valve These do not leak, but the specification shows that at the flow rate of the bilge pumps they give too much counter-pressure, like 3 meters of water column.


It would be nice if you can point out a check valve that does not leak and does not impair the flow too much. And is not made from brass...... And resists seawater.
I might need to install a 1.5" or 2" check valve with hose adapter for 1" to have a good flow.


Thanks!
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Old 26-03-2019, 08:48   #2
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Re: Check valve for bilge pumps?

No check valves, loop the hose up high, under a coaming if you can, etc. You can also install a siphon break up there. Relocate the hull exit if you have to , to do this porperly.
I almost sunk my 44 footer with a check valve. Intuition had me lift a floor board under way for some reason, The water was just under the board!
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Old 26-03-2019, 08:51   #3
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Re: Check valve for bilge pumps?

I would put in a vented loop instead of a check valve.
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Old 26-03-2019, 20:05   #4
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Re: Check valve for bilge pumps?

I have fiber glass scoops that face aft over the the tru hulls
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Old 26-03-2019, 20:36   #5
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Re: Check valve for bilge pumps?

My new-to-me boat has check valves in the bilge line.

Hidden, of course. I found them while spending 3 hours troubleshooting why my bilge pump RAN but didn’t pump. I had to disconnect the outlet, 20 ft back from the bilge, and start feeding the stiff white sanitation hose towards the bilge in order to get the bilge pump out, when we spotted a check valve passing an acces port. Of course, at rest, it lay about a foot out of site. Bronze flapper type, luckily with a service port.

The flapper was sticking to its seat.

I had to “unstick” it 5 or 6 times over the weeks passage home. By feel.

It’s been replaced with a plain splice. A shame, as that 20ft run makes for a lot of backwash. A vented loop isn’t feasible for me.

I HAVE had good luck (no issues) with the rubber flappers built into a jabsco strum box, as well as those built into the diaphragm bilge pump I had on my last boat.

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Old 26-03-2019, 22:03   #6
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Re: Check valve for bilge pumps?

As most above posters said: do not fit check (one-way) valves in any hose of a bilgepump. Below are some reasons:
- any system without a check valve is simpler
- by not having a check valve, one saves the cost of buying, installing and servicing these
- such a check valve WILL reduce bilge pump output, because of the restrictive nature of the valve. BTW, vane bilgepumps are generally high volume/ low pressure, and any obstruction might reduce flow by 10 to 30% (that is my estimate)
- it is a near certainty that, over time, such valve will cease to operate, and water will flow freely back, like there was not such valve
- it is a near certainty that, over time, such valve will completely block the hose, and obviously such blockage is likely to occur when one needs it most.

Solutions has been mentioned: ensure a high loop is routed (well above the waterline), and a vent in that loop is the outlet is (at times) under the water. However best practice is to position the outlet well above the waterline.
If this such loop is not possible, look for other alternatives, ie different kind of pump, make new location for outlet.

There has been numerous threads on this subject. Will find some of those later.
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Old 27-03-2019, 06:29   #7
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Re: Check valve for bilge pumps?

I had the exact same problem on my boat which I seem to have found a solution for. The problem with running your outlet hose high or with an anti-siphon is that you are increasing the height at which the pump has to pump water, thus decreasing its flow, and the problem with check valves is that even the best ones cannot hold water indefinitely inside a hose.

I used a Bosworth one way valve on each hose just inside the hull. The hose from the pump runs to a point slightly higher than the thru-hull and then heads 'downhill' to the valve which sits just inside the hull. This way, when the waves slap against the hull, the water can't get past the flapper. Also, as the valve faces down, the flapper is is the normally slightly open position so there is no resistance to flow and no way for it to become clogged shut.
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Old 27-03-2019, 07:24   #8
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Re: Check valve for bilge pumps?

Quote:
Originally Posted by Privilege View Post
I had the exact same problem on my boat which I seem to have found a solution for. The problem with running your outlet hose high or with an anti-siphon is that you are increasing the height at which the pump has to pump water, thus decreasing its flow, and the problem with check valves is that even the best ones cannot hold water indefinitely inside a hose.

I used a Bosworth one way valve on each hose just inside the hull. The hose from the pump runs to a point slightly higher than the thru-hull and then heads 'downhill' to the valve which sits just inside the hull. This way, when the waves slap against the hull, the water can't get past the flapper. Also, as the valve faces down, the flapper is is the normally slightly open position so there is no resistance to flow and no way for it to become clogged shut.
You should make a high loop then put the throughhull low. The height that you are pumping is measured from inlet to outlet. You only measure to the highest point when the pump starts and the hose isn't completely filled.

When you first start, the pump has to be capable of pumping water to the highest point, once the hose has filled all the way the water on the downhill side pulls, so the net height is from inlet to outlet ignoring any high points.
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Old 27-03-2019, 08:21   #9
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Re: Check valve for bilge pumps?

Why not replace your vane / centrifugal pumps with diaphragm ones, at least for the nuisance pumps? Until the diaphragm fails, it's a self-checking pump, with no vent loop needed. You can keep your vane pump for a crash pump, but don't count on it to save your boat, only to buy you an additional hour while you look for that fountain!
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Old 27-03-2019, 10:55   #10
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Re: Check valve for bilge pumps?

Our boat has a very small bilgewell for the main bilge pump. Without a check valve the residual water in the discharge line flows back into the bilgewell, and the pump cycles on again. On/Off/On/Off.....It would be the same with a high-loop. I installed a check valve, in a very easy to access place, years ago. Only had it fail once, and it failed open. Pulled it, cleaned it out, and put it back. 5 minutes and VOILA! Keep in mind that the Emergency Bilge Pump, which is above the normal bilge waterline, has no check valve, and is free to pump at full capacity without the backpressure/restriction of a check valve.
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Old 27-03-2019, 12:12   #11
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Re: Check valve for bilge pumps?

Quote:
Originally Posted by John_Trusty View Post
Why not replace your vane / centrifugal pumps with diaphragm ones, at least for the nuisance pumps? Until the diaphragm fails, it's a self-checking pump, with no vent loop needed. You can keep your vane pump for a crash pump, but don't count on it to save your boat, only to buy you an additional hour while you look for that fountain!
I'll second this suggestion. How I've dealt with a really deep sump and works quite well.
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Old 27-03-2019, 14:12   #12
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Re: Check valve for bilge pumps?

What Cheechako said. Get rid of check valves--replace with siphon breakers. Simplest is always best
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Old 27-03-2019, 16:08   #13
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Re: Check valve for bilge pumps?

Check valves seem to elicit absolute responses but I think there is room for nuance. I would agree that a check valve should never be used instead of a vented loop - you must install vented loops to prevent back-flow from flooding the boat; for this purpose a check valve is far too risky as others have said. OTOH for a properly installed bilge pump (with loop) a check valve can prevent the unwanted cycling that comes with some installations of centrifugal pumps (i.e. where the water in the hose flows back when the pump stops, triggering the switch and repeating). After 30 years I replaced my joker-style check valve on my main bilge pump, without ever having a failure. Keep in mind that for this use the check valve always has water in the hose above it holding it closed until the pump comes on. If one is concerned about a lower flow rate then buy a larger pump, hose, and check valve. Flow rates on centrifugal pumps drops greatly as the height to pump (to the top of the loop) increases; the check valve is a minor contribution.

You might consider two pumps at each location: one small diaphragm pump to remove small amounts of water and one large centrifugal pump for emergencies.

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Old 27-03-2019, 20:30   #14
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Re: Check valve for bilge pumps?

Loop with syphon !
Had similar problem with check valve only worse. 3 am in the morning, whilst at the helm, was asked by rookie mate down below if it was normal that his feet were wet with 6 inches of water sloshing around the cabin ! Automatic bilge had activated and when it shut off syphoned water straight back into the bilge because check valve, installed by previous owner, had failed. Evidently the float switch failed at that point too. Bilge had been checked 40 minutes earlier.
Installed a syphon in the loop and a second float switch (and second pump) higher in the bilge with an audible alarm !!!
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Old 28-03-2019, 03:42   #15
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Re: Check valve for bilge pumps?

Greetings and welcome aboard the CF, Stephen.
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