Removed check valve from bilge pump- now it won't stop running

[sailor Martin]

I have removed the check valve from the outlet of my bilge pump to prevent unnecessary resistance.

Now whenever the pump stops working, the water rushes back in and the pump kiks into action again. Eventually this will drain the battery.

Simplest solution please?

Already tried relocating the float switch- doesn't matter at all.

I'm thinking about installing the float switch slightly higher than usual and adding an element that will keep the pump running for an extra 10 seconds at least every time. Perhaps a special float switch with a delay on opening the circuit?

Cheers
Martin

[marshmat]

That's precisely what the check valve is for. If you're worried about the (very slight) extra resistance of the check valve, then put it back in anyway, and replace the pump with one a size bigger.

[BillKny]

Originally Posted by marshmat

That's precisely what the check valve is for. If you're worried about the (very slight) extra resistance of the check valve, then put it back in anyway, and replace the pump with one a size bigger.

^^^Bad advice^^^ Check valves in bilge discharge lines are just considered very bad practice. Any good surveyor would make their removal a high priority,

There are a LOT of reasons to NOT have a check valve in a bilge pump discharge line. Risistance is one. How much resistance really depends on the type of valve, but it is not necessary and shouldn't be there.

But the real issue is that they are unreliable. The can stick open, and it's like they are not there. They can clog with even small pieces of debris from the bilge and then block discharge. Just say NO to check vavles in bilge lines. They are a lazy crutch to correct bad designs.

It can be tough for an inexperienced boat owner to sort out exactly how to plumb and switch a bilge pump so a check valve is not needed. It is really hard to give general advice, because it depends on the situation.

Usually the best solution is to have a very small pump with skinny lines that don't hold a lot of water in the very bottom of the bilge to handle routine drips and such. The smaller lines don't drain back enough water to re-tirigger the float switch. Then a larger pump higher up in case of larger influx of water, or failure of the primary pump.

Another option is to use one of the several of the electronic water level switches that incorporate a built in timer so the pump runs 30 seconds or so after water level drops below the switch.

A third option is to use a diaphragm type pump mounted above bilge level.

There are others...

[cal40john]

There are others, but here's an electronic float switch with delay -
https://waterwitchinc.com/bilge-switches/

Or raise your big volume pump up a bit and add/install a low volume diaphragm pump or dry bilge system that are now coming out.

https://www.google.com/search?q=diap...hrome&ie=UTF-8

https://www.google.com/search?q=dry+...hrome&ie=UTF-8

[rwidman]

I agree with BillKny, a check valve in a bilge pump outlet is a very bad idea.

If your boat came from the factory with this design, shame on the manufacturer. If a previous owner did this, shame on him.

The solution depends on the boat and there are a lot of variables, but basically, the thru hull for the bilge pump is too high up from the pump. You may be able to relocate the thru hull lower, but still above the waterline.

A smaller diameter outlet hose will hold less water, but it may restrict the pump. Check the specifications of the pump.

As a "last resort", you could have the bilge pump pump into a small tank a couple feet above the bilge and install another bilge pump in that tank to empty that tank overboard.

[svfinlandia]

Originally Posted by cal40john

There are others, but here's an electronic float switch with delay -
https://waterwitchinc.com/bilge-switches/

+1 on the Waterwitch switch. I have used one for years and they were great.

Al, S/V Finlandia

[zstine]

I had the same issue. a delay in the switch did nothing since as soon as the pump sucked air, no more water flows and the tubing stays full of water anyway... so it still drains back into the bilge and turns the pump back on. putting in smaller line and arguing against check valves is kinda an oxymoron. smaller lines increases restrictions and likelihood of clogging... so just use a check valve.
You can try putting the float switch higher so that the water that backflows doesn't reach high enough to set it off. make sure you have a shipon break.... you will always have a wet stinky bilge.
I don't like a wet stinky bilge so I ended up putting a check valve back in. never had it cause a problem in 8 years... yes it leaks and needs cleaning or replacement about annually

[Secondshift]

Originally Posted by marshmat

That's precisely what the check valve is for. If you're worried about the (very slight) extra resistance of the check valve, then put it back in anyway, and replace the pump with one a size bigger.

Your current system design obviously relies on the valve.

Check valves DO NOT sink boats.
POOR MAINTENANCE sinks boats.

You could redesign with a smaller lower level pump with a check valve.

Best Regards

[sailor Martin]

Thanks for the link!

[TrentePieds]

No need to get terribly scientific about this, but it does help to be cognizant of the numbers involved.

Have a quick look under your kitchen sink. There is your answer :-)! You'll see that the pipe from the sink goes through a 180º bend, rises for a little way and then goes horizontally into the wall. It's called a “P”- trap for obvious reasons.

You ought to have an upside down “P”-trap on your bilge pump :-)! The through-hull should be mounted high enough that when you heel the boat 15º, or so, to the side where it is, the through-hull won't be submerged. This is to preclude “siphoning”.

A Rule 2000 pump will lift about 1,300 gallons per hour to a distance of 6 feet. So sez Rule. Let's assume we believe them :-). So you drive the water up some distance above your waterline, take it over the top of an inverted 180º bend and then down to your through hull. These pumps have a 2” outlet, so that will be the diameter of the pipe or tube or hose you use.

You will agree that the interior cross-sectional area of a 2” tube is 3.1416 x (2/2)^2 = 3.1415 square inches and that 6 feet = 72 inches. Therefore the quantity of water than will be in the riser when the pump stops is 72 x 3.1416 cubic inches = 225 cubic inches, or just a tad less than a gallon. Because the pump is a centrifugal, self-priming pump, this water will all fall back into the bilge when your pump stops. Can you live with a bilge that always has a gallon of water in it? I can. If I want ALL the water out, I mop up that residual gallon of water with a sponge.

Now, 1,300 gallons per hour = 1,300/60 = 21 gallons per minute. Short of a catastrophic hull failure, how are you ever going to get so much water in your bilge that your pump can't dispose of it in under a minute? Bilge pumps are for “tidying up”. Not for “saving the ship” If you get water in you bilge constantly, or even just frequently, the pump is the LAST thing you want to be thinking about. The first thing to think about is where the water is coming from, and when you've determined that, you take whatever remedial action is apposite. When THAT's done you can use the pump for “tidying up” :-)

The float switch is a somewhat separate issue. It should be mounted at a height in the bilge that permits the residual gallon of water to lie there without lifting the switch and activating the pump. But it should also be low enuff to permit no more that a tad more than a gallon of water in the bilge before it triggers the pump. Mine is mounted on a little platform at the bottom of a strake that attaches to a floor by means of a wing nut. Thus I can easily pull it out for servicing. It is also wired so a "Normally Off" push button on my instrument panels permits me to bypass the float switch and operate the pump from the navigation station.

Hope that gives you something to think on :-)

All the best!

TrentePieds

[mitiempo]

Originally Posted by sailor Martin

I have removed the check valve from the outlet of my bilge pump to prevent unnecessary resistance.

Now whenever the pump stops working, the water rushes back in and the pump kiks into action again. Eventually this will drain the battery.

Simplest solution please?

Already tried relocating the float switch- doesn't matter at all.

I'm thinking about installing the float switch slightly higher than usual and adding an element that will keep the pump running for an extra 10 seconds at least every time. Perhaps a special float switch with a delay on opening the circuit?

Cheers
Martin

The best solution I have found is a small pump (350 or 500 gph) in the lowest part of the bilge with a check valve. This is the daily dewatering pump to keep the bilge as dry as possible. This pump will not move a lot of water but on a daily basis it doesn't have to.

A larger pump (1500 or 2000 gph) is mounted higher in the bilge with a float switch also mounted higher. This is the pump that will move a lot more water when necessary. This pump should not have a check valve. It should only come on when the water is higher.

[guyrj33]

"... option is to use a diaphragm type pump mounted above bilge level."

Diaphragm pumps have check valves, it's part of the pump design.

So, if check valves are bad why are diaphragm pumps recommended?

[garychurch]

Your cure of removing check valve is worse than symptom. Put the check valve back in before you sink your boat.

[marshmat]

The check valve should never be used to prevent water from coming back in from the outside. That's the siphon break's job. You can't rely on a check valve to do this; it's risky, unreliable, and would fail survey.



A check valve, if fitted, is just to stop what water is in the hose between the pump and the siphon break from coming back down into the bilge when the pump shuts off. They're used for this all the time, and I'm not sure what the concern would be in doing so.

[donradcliffe]

Originally Posted by guyrj33

"... option is to use a diaphragm type pump mounted above bilge level."

Diaphragm pumps have check valves, it's part of the pump design.

So, if check valves are bad why are diaphragm pumps recommended?

Because check valves are good. Diaphragm pumps actually have two check valves in series.

The only really important thing about all bilge pumps is to have their discharge above the water line so they can't siphon.