Sometimes, Stuff just happens
One take-away is the combined effect of "Murphy" and "entropy".
Our club now has a spiffy new dredge, which in simpler parlance is a large steel box/barge with a huge 6" pump and diesel engine in it and an inlet for outside water to be brought in for pressurizing the packing seals on the main shafting where all the sand is being pulled through. (the slurry pipes are not as vulnerable.)
Couple of years ago when we were operating the prior machine, after a several days of shut down in operations, I and my one person crew showed up and found almost two feet of water inside. Bit of a surprise it was. Yes Indeedy. :0
We engaged the small 12 volt centrifugal pump we use for incidental water while operating normally, and then tried to figure out what failed with our two (2 !!!) AC powered "sump pumps" in the dredge, each with its own float switch. We found that one float switch had stopped working and the other was mounted wrong and initially failed.
The de-watering was done quickly and no harm done to the diesel (water level just lower than the dip stick and barely starting to cover the 8D battery box.) We were pretty motivated, as well.
The cause was a bad ball valve on the sea chest that would not quite seat, and one of the crew had loosetened the hose from that part due to several days of freezing temps and the need to preserve the high-pressure pump mounted low on the bottom. A small seap took time to add up, but add up it did!
After the crisis was averted, I replaced and reconfigured the mounting for both float switches and they tested out perfectly... and last year we sold that old dredge... and instructed the new owenrs about its many quirks.
My point, and I thought that I had one, is that total 100.00% assurance that all water will always be kept out is not realistic. But we do the best that we can! And that's good enough most.... of the time.
Regards,
Loren