20 seacocks seems extreme. I have one for the sink drain, which I rarely close, and one for the watermaker, which is closed most of the time. I have two seacocks, total.
I suggest you try think of ways to eliminate most of those seacocks.
Standpipes can reduce the need to close some.
I suppose, but see post #47. The 20 count was just the original "off the top of my head" estimate. There are actually 26!.....wow, with about another half dozen thru hulls without seacocks.
I could theoretically combine some, as they are all essentially in 6 distinct locations. There are four separate heads aboard (one is a dedicated shower with no toilet) plus the galley. To those five locations, you add the floorboard next to the engine and those are my 6 stops to open/close. I'm serious when I say, its a 2 minute operation. Each head has a sink drain and floor sump, which could theoretically be combined. I suppose the dishwasher drain could be combined with the galley sink, etc.
However, it wouldn't really make that much of a difference, there will be a ton of holes in the boat, no matter what. Maybe I could realistically get it down to 16 or 18? I can't combine intakes with drains (there are five sinks, three toilets, three airconditioning units, two motors, alone). I would still be visiting each of these locations to close the combined seacock, so why not flip a few levers instead? It takes no additional time. The upside to the current configuration is that I can close off single systems to work on them, without taking others offline.
If I was doing it from scratch, I would seriously consider some combining. I'm the boat's second owner. However, I have a ton of priorities and wish list items in my maintenance log, like AIS, which I would do long before hauling, combining thru hulls and patching over old ones.
I will continue to close most when we leave for more than a day, regardless of how many I have. It's good for the ball valve anyway. It also forces me to check on leaks or valve issues, which I think I would notice before many who never touch them.
Thanks for the discussion. It has been fascinating how many different practices there are.