Isolating Taps?

Aug 21, 2019
156
Catalina 315 18 Grosse Pointe Park, MI
On my new 315, just forward of the engine, under the cabin sole are these, each labeled "isolating tap." Does anyone know what these are, how they are used and whether I need to do anything to them when I Winterize the boat?
 

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Oct 22, 2014
20,995
CAL 35 Cruiser #21 moored EVERETT WA
Scuttle valves? I wouldn't open them if that the case.
I think Submarines had scuttle valves to keep the boats secret incase of invasion. Just think. You get a grand prize and jump aboard to enjoy and the sucker sinks beneath your feet. Very demoralizing.
 
Aug 21, 2019
156
Catalina 315 18 Grosse Pointe Park, MI
I would imagine that these are connected to the potable water system. But, there were nothing like these on my old boat and I am thinking they must have some specific purpose. I am hoping someone might know what that is.
 
Jul 23, 2009
857
Beneteau 31 Oceanis Grand Lake, Oklahoma
Low point drains are used to drain the fresh hot/cold lines for winterizing or maintenance proposes. Lots of RVs have them.