Blige pump bleeds back

[Kevin Kaldenbach]

I have two bilge pumps and both bleed back into the bilge. The rule 1500 has a check valve that I replaced thinking it would fix the problem but it did not. I then bought a whale 650 and it does the same thing. The thru hull is way in the back of the boat so what bleeds back into the bige is enough to turn the pump so there is this see saw action going on. When the pump turns on there is not even enough water to go out the thru hull. Any advice? Prehaps a vented loop? Find a differen place to give the hose a shorter run? The boat is a CD31

[Sea Hunt Video]

Kevin:

I preface my comments by stating I am a true rookie and tadpole at this stuff. On the plus side I have been reading about positioning and installing bilge pumps.

Have you considered positioning one or both of the bilge pumps higher up in the bilge so that they only activate when water reaches a certain pre-set level that you determine by where you install the bilge If you have a manual bilge pump and hose (I do not know the Cape Dory 31 bilge area) you could use this to pump out what water is below either or both of the electric pumps.

Also, in looking at the Whale 650 literature it say there is a part you can order to prevent back flow.

Optional In-Line Non-Return Valve available - Part number LV1219

Don Casey has a brief article on setting up two bilge pumps in one of his online websites. I think this is it but I am never good at copying website site locations. Sorry.

http://www.boatus.com/boattech/casey/14.htm

[eb1smith]

Kevin: The 'return' water is because the lift height is what is causing the flow back. A step down in hose size might help.

-Eric

[hilbert]

Check valves are a source of problems on bilge pumps. A small pump has a small diameter hose, which minimizes backflow, water in the bilge and pump cycling. A small pump also has the advantages of small current drain and the cost of carrying a spare pump is minimal.

I selected a Water Witch electronic control, which helps reduce cycling. It has an on delay of 6 seconds to avoid pump stutter and it continues to run for 14 seconds after the water leaves the sensor. The switch has no moving parts and it will not activate if the bilge fills with oil or diesel. It can turn on a larger auxilary pump (and/or alarm), after a 2 minute delay.

I am building a frame to place the pump at the lowest point and still be easily pulled for maintenance. The height of the Water Witch can be adjusted by sliding it up and down on the frame.

[JWSutcliffe]

Kevin:

Had the same problem on my 31. I eliminated the cycling by reducing the total volume of trapped water in the exit hose by slightly better hose routing back to the through hull, and replacing the hose with the next smaller diameter (as others have suggested here.) The previously installed hose was a larger size than the pump outlet anyway. However, the real key is to eliminate the leakage into the bilge. Once I put in the dripless seal last summer I never heard my bilge pump run again.

[Klem]

I was able to largely eliminate this by moving the vented loop so that it is as close to the pump in the horizontal as possible but it is still at the same height vertically. This greatly diminished the volume of trapped water before the vented loop. Also, the previous owner put the float switch just above the sump so that it takes a significant amount of water to trip it due to the bilge geometry. The only time that I have cycling problems is when we are rolling really badly and manually running the pump to get the water level down solves this issue.

When I worked commercially, I tried check valves and could never make it work. They wouldn't seal reliably so the water would still drain back, it would just take longer. Also, there seemed to be a significant pressure drop across them and the pumps couldn't overcome it when they were in a deep bilge so they didn't work at all. Maybe someone else has found a way to get them to work?

[sharkbait]

Kevin,

The only solution I know of is to use a diaphragm type pump which will totally evacuate the line.

[ckreitlein]

On my CD30, I have an automatic bilge pump and an in-line check valve, followed by a long discharge hose of at least 6 feet with no loop leading to the overboard discharge. The six foot discharge hose holds a lot of water downstream from the pump, but it did not return to the bilge and my pump does not cycle on and off - because the CHECK VALVE WORKS. Unless you have another problem (hole in the discharge hose, an undetected leak elsewhere, etc) I cannot see why your bilge pump hoses would leak back, past the check valves, into the bilge unless the check valves are bad. Before making loops and all the other stuff, test your check valves somehow. You might try disconnecting the discharge hose from the overboard discharge and blowing in it to see if the check valve is indeed doing its job.