First off, for anyone planning to do coastal cruising of any sort, please consider taking a Safety at Sea course. I took my first before a Bermuda Race about 20 years ago and still use lessons from it. The courses are meticulously designed, presented, and updated by experts who really care about keeping people safe at sea. I've sat through plenty of courses on plenty of topics "just to get the badge" but Safety at Sea courses are so worth it. This post is not by any means an attempt to replace a Safety at Sea course, rather hopefully it awakens your interest in the topic and convinces you to register for one.
That said, let's have a look at some of the key topics around water in the boat. Many of these come from Safety at Sea curricula, others come from the unique perspective of being within earshot of Will Keene most days. Will thinks and talks about these issues more than anyone you could imagine (seriously!). Edson sells pumps, and we sell great ones. Edson's first product was the manual diaphragm pump, and its offspring are still some of our most important products. Though the superiority of Edson pumps relative to the other pumps on the market is easily demonstrated, the purpose of this post, and the blog in general, is much more educational than sales. If you are serious about moving water out of your boat, there's one choice.
The biggest lesson I've taken from the best practices mindset of safety at sea is to look at your boat and think like water that REALLY wants to get in there. Not just the annoying drip when it rains - the volume and pressure of a wave that rolls over the hull and potentially rolls the hull over at least momentarily. That ounce of prevention again.
One great excuse to have a clean bilge, painted white, is to clearly mark the waterline inside the boat. When there is water in the boat, this gives a reference for how big the problem is, and gives a reference on whether you are gaining or losing ground against the water. The farther below the waterline a hole is, the faster (by far) water will come in. A 1" hole 2 feet below the waterline can sink a boat in minutes.
If a volume of water unexpectedly appears in the boat, a smart first move assuming you're on salt water is simply to taste the water, assuming it's not obviously risky to do so. If it's fresh, you probably have an "inside the boat" problem. If it's salt, you've got a bigger problem.
The triage protocol when faced with an obviously significant water ingress issue is determining whether the water came from a one-time event like a wave across the deck, or if there's an ongoing water problem. Your choice set will be whether to stop or profoundly slow new water coming in (if possible, this is your A choice), or immediately reduce the amount of water in the boat, or if you are in a situation like Kevin Escoffier in the last Vendee Globe, to abandon.
Above the waterline ingress can be just as catastrophic as below the waterline. Deckhouse windows, hatches, companionways, lazarette doors, dorade vents, mast partners, and any place that water can get in the boat needs to be looked at from the worst case scenario - how much water could get in here, and what effects would that cause?
Below decks, every through-hull fitting needs an appropriately sized plug tied to the fitting and accessible in case of failure. The classic hardwood bungs work well, and there are also innovative solutions like the Forespar Sta-Plug plugs. These offer the chance to significantly reduce water ingress and make the problem smaller.
The Offshore Racing Requirements, while good guidelines to what you might need, are minimums. Some gear that fulfills requirements won't necessarily be the best answer. For example, the permanently installed manual bilge pumps need a 10GPM (gallons per minute) capacity to meet rule requirements. 10GPM is inadequate for a bad situation - we have 18 and 30GPM options in both cockpit- and below-deck operated models.
Any serious passage requires a serious examination of the safety issues you might face, and preparing for them. Water ingress is always the most serious problem, and the value of a great pump should never be underestimated.