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Bilge Pump - Siphon BACK!

Apex

.
Jun 19, 2013
1,052
C&C 30 Elk Rapids
Our double-handed trip from Muskegon to Elk Rapids was eventful: First day we were sailing, and found the bilge FULL. Turned around, as we thought it may be the packing gland. After adjustment, careful scrutiny, we found that 1) the icebox pumps into the bilge, and then when activating the bilge pump underway it will siphon back into the boat, and then some.

Beyond that, day2:
20kts, apparent angle of 120, and 8-10ft seas. Max speed: 9.9kts surfing, and average 7.3kts over an 8hr day. Full sail all day, main and 135genoa.
day3:
Motor would not start. Got it started and chose to motor sail every other hour to keep things charged. 20kts, apparent angle of 90, and 5-6ft seas. When actually sailing It took a bit to balance the sails and found a groove around 7kts when the stitching for the webbing at the head of the jib let go. Manual sewing even with a palm resulted in 2 broken needles and -0- stitches.
day4:
0-10kts, flat seas and motor-sailing with main alone for a 13hr day. Flew the spin for 2minutes before the wind shifted again.

all out total 187 miles,, exhausted and a long list of repairs and improvements looming. First up is safety for
 
Oct 24, 2010
2,399
Hunter 30 Everett, WA
Sounds like a tough trip. Hours are usually pretty much uneventful.
 
Jul 19, 2013
317
Pearson 31-2 Boston
If the bilge pump outlet is below water when the boat is heeling, and there is no check valve or anti-siphon loop, then it is possible for a bilge pump to run in reverse. William Buckley's excellent sailing book AIRBORNE tells the story of his yacht sinking at the dock for an un-determined reason, later in the same circumstances as yours, he figured out it was the bilge pump.
 
Apr 8, 2010
1,620
Ericson Yachts Olson 34 28400 Portland OR
One of the best ways to address the dangers and shortcomings of a centrifugal pump (like the cheap and ubiquitous Rule brand) is "shot put" it out into deep water.... A frustrated mariner often gets 75 to 100 feet with a good wind up.
:(
Then install a reliable pump with built in check valves like a Jabsco 37202 model. Mount it remotely from the pickup point in the bilge where you have your strum box on the end of the hose.

Finally, open a beer & celebrate your nautical wisdom!
:)

Many of us have learned your lesson, the same hard way...
 
Mar 1, 2012
2,182
1961 Rhodes Meridian 25 Texas coast
If the bilge pump outlet is below water when the boat is heeling, and there is no check valve or anti-siphon loop, then it is possible for a bilge pump to run in reverse. William Buckley's excellent sailing book AIRBORNE tells the story of his yacht sinking at the dock for an un-determined reason, later in the same circumstances as yours, he figured out it was the bilge pump.
Easy to solve- an anti siphon loop. I once had the bilge fill coming in from 30 miles offshore, to where I had ankle deep water:( in in the cabih-installed an anti siphon loop and voila - no more problem- many many miles later.
 
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Likes: RoyS
May 24, 2004
6,789
CC 30 South Florida
It is normal to have some backflow of water into the bilge when the pump stops. There are also more than a few gallons of water trapped on the hull stringers below the sole. When the boat is in motion, especially in high seas some of this water will be released and it flows into the bilge. It may seem like a never ending river of water, but it should never overflow the bilge. The source of the water trapped is usually, rain leaks, Fridge drains, plumbing leaks, wash downs, wet bathing suits, galley spills, sea spray. The water will go bad due to bacterial contamination and with time some of it will turn into a goo and will stink. There is plenty of information into the archives including some extreme measure to try and get the last drop out. Your bilge pump outlet port should be above the water line and although it may be submerged when the boat is heeled the speed of the water rushing across the opening will suck out most of the water that may enter. The electric bilge pump is merely a convenience item to help drain incidental water that enters the bilge. Your boat should be equipped with a manual gusher pump that can be operated from the cockpit. If not installing one would be a must upgrade. That pump is designed for emergencies. An engine that fails to start after running in high seas could be a sign of sediments getting dislodge inside the fuel tank and possibly clogging the filters causing fuel starvation or air leaks into the fuel lines. Those trips are fun, aren't they?
 

Apex

.
Jun 19, 2013
1,052
C&C 30 Elk Rapids
It is normal to have some backflow of water into the bilge when the pump stops. There are also more than a few gallons of water trapped on the hull stringers below the sole. When the boat is in motion, especially in high seas some of this water will be released and it flows into the bilge. It may seem like a never ending river of water, but it should never overflow the bilge. The source of the water trapped is usually, rain leaks, Fridge drains, plumbing leaks, wash downs, wet bathing suits, galley spills, sea spray. The water will go bad due to bacterial contamination and with time some of it will turn into a goo and will stink. There is plenty of information into the archives including some extreme measure to try and get the last drop out. Your bilge pump outlet port should be above the water line and although it may be submerged when the boat is heeled the speed of the water rushing across the opening will suck out most of the water that may enter. The electric bilge pump is merely a convenience item to help drain incidental water that enters the bilge. Your boat should be equipped with a manual gusher pump that can be operated from the cockpit. If not installing one would be a must upgrade. That pump is designed for emergencies. An engine that fails to start after running in high seas could be a sign of sediments getting dislodge inside the fuel tank and possibly clogging the filters causing fuel starvation or air leaks into the fuel lines. Those trips are fun, aren't they?
Good points Benny. The siphon is most definitely from running the bilge pump while in rough seas. We replicated on multiple occasions. By knowing what and why, it became much less scary and manageable with the hand bilge pump. I traced the bilge pump line from the bilge all the way to the exit. One continuous hose (smooth ID at least) and it is not a vented loop. The inlet is at the bottom of the transom, so underway is in contact with the water. Once the bilge pump shuts off first time, the siphon begins.

I think it is crucial to have an operational pump underway, so now know a separate check-valve in-line is not recommended. I did not know if an anti-siphon loop was recommended, to which it appears "yes, only when necessary". @FastOlson recommendation for a pump with built in check-valve re: Jabsco seems a reasonable solution also. I will look at both options. or perhaps install both a la belts-and-suspenders approach. I am thinking a 2nd pump and alarm anyway. The bilge is small: arms depth, so perhaps 10 gal at most before it is in the flat part of the bilge and then that is only 1" to the floorboards. so a 2nd pump (3rd if you count manual) may be unnecessary