R29-CB Bilge pump--"Mystery of the Disappearing Water"

[PlanetoSea]

Hello all,

I have a genuine mystery o my hands that I cannot puzzle out. Here is the situation: I have security cameras on my boat, and I got a motion alert this past weekend. I looked at the camera, and I saw the wash down crew on board washing the boat, but I also heard the distinct sound of the high water alarm through the camera. I called the owner of the wash down service and she talked to the crew. I watched on the camera as they opened the engine hatch and looked into the bilge to check for water, and there was no substantial amount of water--just a small amount sloshing around in the very bottom. The boat was locked, so there was little they could do about the alarm. So, my daughter went by a little later with keys and turned off the alarm. She turned on the manual switch for the aft bilge pump and it pumped out the water still down there. It ran for about 15 seconds to clear out the remaining water and the high water alarm reset no problem. It is not unusual for a lot of water to get down in there during a wash down, and for it to keep partially filling for a while as the boat dries and runoff keeps finding its way down there, so I am 95% sure the wash down was the source of the water. There has been no water accumulation in the bilge since. So, the mystery is:
[*] If the automatic pump feature was working to clear out the water, how did the bilge fill up far enough to trigger the high water alarm?
[*] If the aft bilge pump automatic feature was dead (as I later confirmed and had to swap out the pump...), then I know how the high water alarm could come on, but how could the water level get back down to just a couple of gallons sloshing around in the bottom?
[*] It turns out my forward bilge pump is dead as well, so there was no pump operation once the high water alarm was triggered.
[*] Any theories on how the water got high enough to trigger the alarm, but could still be pumped out and then have the automatic feature of the aft pump test as dead later that same day?

I am at a complete loss on this one, so I have no idea what else to check, or what else I may need to watch out for in the future. As stated, I did test both pumps, and the manual switch of the aft pump still worked, but automatic was dead, so that pump is now replaced and all is well. Forward pump is dead entirely now, so I have the new pump and will replace that one this Saturday. Any opinions out there on what must have happened, in what order?

 

[knotflying]

There are a couple of things that could have happened and at this point only guesses. A question though; Are the pumps and high water alarm the sensor type seperate from the pumps or float type. The sensors do malfunction and can also "get stuck" in the on position if they are not clean. So perhaps assume there was so much water entering the bilge the front pump could not pump enough or the impeller had crud and was not pumping efficiently. The forward pump was inoperative. The alarm sensor engaged and because of film stayed on. Then the aft pump continued to pump and the washer stopped with the water and by the time they opened the hatch the water got pumped out because they stopped. I had replaced all my sensors with a float. Never had an issue after that. As a periodic maintenance item I would run the pumps on manual a little and then lift the floats to confirm they were working.
At this point we can only guess what happened. The important thing is to make sure all is working correctly now.

 

[Ralf H]

Hi PlanetoSea,

As knotflying mentioned, there isn't really much that we could deduce without being able to diagnose the pumps. As he also said, it depends on the type of pumps you have, whether it is the previous models we installed with a float switch, or the current pumps that cycle once every couple of minutes. One other question is why the alarm would sound when there is only a small amount of water in the bottom of the bilge. If you have enough water in the bilge to set off the alarm, you have way more than just 15 seconds of water to pump out. Not sure but perhaps you have added a second sensor. The original one sits in front of the engine, above the stringer level. To trigger that, it would have filled the bilge with probably 50 gallons or more (have never measured it exactly, so don't quote me on that) Sorry that I don't have a clear answer at this time, but if you have more details that you can share, just let us know.

Cheers,

Ralf

 

[PlanetoSea]

Thanks for the inputs so far. I thought I was answering the type of pump question with the bullet about the automatic feature of the aft pump being dead when I got to the boat and both the automatic and manual switches being dead on the forward pump, but I can see how that still was only part of the picture, as a float switch can also be automatic. Also, I only have the single high water alarm sensor that is wired with the forward bilge pump (at least as far as I know--if there is another, that would be great to know and could provide a missing piece of this puzzle). So, to try and clarify a bit more on my end, both pumps are Rule 1100gph automatic pumps that are identical to the ones that came with the boat. In fact, the forward pump is the original as the boat is only about 4 years old, I have had it for 2, and the original owner did not have any issues with it. So, if the automatic cycle feature was already dead on the aft pump, that could explain how the bilge filled with water high enough to trigger the alarm, but leaves me wondering how, then, did the bilge empty back down to just a gallon or two by the time the wash crew opened the engine hatch while I was watching on camera? The only theory I can come up with is the wash down crew left a hose open and flowing in the cockpit, and that started right after a 2 1/2 minute cycle, so the bilge filled for 2 1/2 minutes, then perhaps the pump outflow was not quite as high as the hose inflow, so the pump starts trying to get rid of the water, but is losing the battle and the bilge slowly fills, triggers the high water alarm, the crew figures something is wrong and moves the hose (or happens to move to another part of the boat so water stops flowing), and the automatic pump feature eventually gets most of the water out before it actually physically fails. Then when I check it later, the automatic feature is dead, but the manual switch still works. That seems like a lot of weird circumstances that would have to align pretty cleanly to be plausible. I keep coming back to the question of "If the pump automatic cycle feature was working, the bilge should never have filled up, so if it was dead, and the bilge filled up, how did the water then get out?" I've got to be missing something here....