bilge pump cycling - any ideas?

craig · Post by **craig** » Jun 16th, '10, 17:10

our new to us cd 27 is set up with a rule 2000 pump and a float switch, both attached to a board which sets in the bilge. when enough water gets in to activate the switch, the pump runs fine but then it continues to cycle on and off after initially emptying the bilge. i believe the water in the hose is draining back down and raises the water level enough to activate the switch.
however, the boat came with this setup and it apparently worked for the previous owner. as it is now the pump eventually drains the battery dead if we are not on the boat.
no, the boat does not make much water but with big rains, wet sailing, or melting ice from the fridge we have to remember to manually pump the bilge before leaving the boat.
i have read elsewhere that check valves are a bad plan. i have a new pump and switch ready to go in but would like some input as to what might be going on.
thanks for your help.
craig

Neil Gordon · Post by **Neil Gordon** » Jun 16th, '10, 17:37

The float switch should have sufficient "play" so that it can lift a bit before tripping the switch. It's possible that somewhere between you and the former owner, the fore and aft trim of the boat has changed and the switch is no longer level.

No need to change the trim of the boat... see if changing the trim of the switch makes a difference.

Russell · Post by **Russell** » Jun 16th, '10, 18:04

I agree that the issue is with the switch. Take it out and clean it up, sometimes some gunk on the hinge is fouling it. Worst case you need to buy a new switch, they do tend to have a pretty high failure rate, so its not abnormal to have to replace it.

johnny of STORK · Post by **johnny of STORK** » Jun 16th, '10, 18:06

Mine did exactly the same thing. I solved it by getting one of the "smart" switches that runs on for 10 of 15 seconds after it no longer senses water. We'll see if it is as durable as it is smart.

Johnny

Ed Haley · Post by **Ed Haley** » Jun 16th, '10, 18:11

You need to prevent the water left in the drain hose after the motor shuts off from draining back into the bilge. Install a check valve in the line about 12 inches or so after the pump. This is a one-way valve that lets water be pumped out but keeps the water from flowing back into the bilge. Be sure to install it correctly. Blow through the valve to see which way it allows water passage.

Ron M. · Post by **Ron M.** » Jun 17th, '10, 07:25

check valves........not a good idea on a boat. Instead, reduce the diameter of of the hose. It will cut down on the amount of water that drains back.
See Casey's 'This old boat' for a diagram and explanation.
You can also install one of those float switches that will allow you to adjust the level it activates.
________
Jugallette

Neil Gordon · Post by **Neil Gordon** » Jun 17th, '10, 07:45

Ron M. wrote:Instead, reduce the diameter of of the hose. It will cut down on the amount of water that drains back.

Won't less diameter reduce the effective capacity of the pump to empty the boat?

Can you accomplish much the same by adjusting the loop so that it peaks closer to the pump and further from the overboard discharge?

GLutzow · Post by **GLutzow** » Jun 17th, '10, 07:57

Recall that the top of the loop needs to be above the water line of the ship.

Neil Gordon · Post by **Neil Gordon** » Jun 17th, '10, 08:09

GLutzow wrote:Recall that the top of the loop needs to be above the water line of the ship.

Yes, of course, and I wan't suggesting lowering it, just reducing the distance between the pump and the peak of the loop. Less volume to drain back into the bilge that way.

rtbates · Post by **rtbates** » Jun 17th, '10, 08:24

while I never had the cycle problem with sit in the bilge centrifugal pumps, I always had the drain back issue. A check valve in the output didn't work because the output of the centrifugal pump didn't have enough pressure to open the valve. My answer was a remote diagraphm pump(Jabsco) mounted high in a cockpit locker with a strumbox with built in one way valve. Now the pumps suction works the valve. My bilge switch is a 'smart Bilge' switch. It's a float in a tube that raises and lowers a magnet that activates the switch.
I gave up on 'sit in the bilge' type centrifugal pumps after my third one failed to operate simply becasue it had a few strands of hair wrapped around the impeller. Not a good design for something that is relied on when I'm not there.

Bob Condon · Post by **Bob Condon** » Jun 18th, '10, 08:20

West Marine sells a plastic check valve for this applictaion. I have used one for 8 years without any issue.

In your winter shutdown list, remove the checkvalve and let the water in the line drain so as to not freeze.

I put the valve about 3" from the pump in the bilge.

simple fix and the problem goes away, takes longer to order than install. use 2 hose clamps

1/2" Plastic Check Valve 308593 FV1227 In Stock $10.99

Carl Thunberg · Post by **Carl Thunberg** » Jun 18th, '10, 13:44

I'm aware of the prevailing wisdom that you should not have a check valve in your bilge pump hose. I disagree with this wisdom for one reason: siphoning. On Leona Pearl, the bilge pump discharge is only 6 inches off the water line. On a port tack in following seas, the bilge pump discharge can get submerged. Imagine the bilge pump kicking on at the same instant the through-hull fitting gets submerged. You've instantly primed a siphon. I don't care how high the loop goes. It makes no difference to a siphon. This happened to us twice and it was very scary. It stopped as soon as we installed a check valve. Another solution would have been to move the bilge pump discharge higher above the water-line, but we chose not to make a bigger project for ourselves (there were plenty more immediate projects).

I'm not suggesting this is your problem, but it does make you think.

John Hpiller · Post by **John Hpiller** » Jun 18th, '10, 14:51

i installed a check valve on my 27 after I developed a siphon in similar to the above conditions. Going below on a beautiful day to find 8" of water over the floor is unpleasant. (about 25 miles NE of abacos)

What is the reason why check valves are frowned upon?

Ed Haley · Post by **Ed Haley** » Jun 20th, '10, 04:56

Check valves work well in this type of application whether it is frowned upon or not.

In some cases, if there is a lot of small solid pieces in the bilge, the debris can be pumped to the check valve and accumulate in the valve preventing the valve from opening. There is a LOT of pressure from the pump but that pressure can't clear the blockage. If the pump is running and there is nothing being pumped out, that's a clue there is a blockage. The blockage must be removed before the valve can open.

There is also the issue of two more hose clamps that can fail.

Another reason, if you do have an electric bilge pump, be sure to exercise your manual pump once in a while so the flappers in the pump don't dry out. If they do, you won't be able to use your manual bilge pump.

Steve Laume · Post by **Steve Laume** » Jun 20th, '10, 07:03

I installed a Johnson electric bilge pump this winter to use for emergency de-watering. I have a Whale Gusher 10, manual in the cockpit for my primary pump.

The new electric one is set up without a float switch and no check valve.

One nice feature of the Johnson pumps is that they have a check valve option built right into them. It is a simple rubber flapper that can be installed right at the screw in hose barb fitting. This makes perfect sense in that none of the hose water drains back and it requires no additional hose clamps.

The thing could only cost pennies and it gives you an easy option to have a check valve. The literature did mention that it will reduce capacity.

The check valve will always reduce flow, it could clog to further reduce output and a slight sticking would still allow a siphon.

No one has mentioned a vented loop as an option. Wouldn't this prevent siphoning with little risk of clogging and no reduction in flow?

The easiest solution to all of this might be to turn off your automatic bilge pump when sailing, Steve.

The Cape Dory Board

bilge pump cycling - any ideas?

bilge pump cycling - any ideas?

You need a "check valve" in bilge pump drain

check this

Re: check this

Check Valve

Another advocate for check valves

Plugged check valve