Isolation manifolds, where the solution to fix one leaking o-ring is to add 5 more (or 4 and a crush washer).
People go on and on about not adding failure points, but the weakest link in any valve is the handle and the serviable guts. So how does it make sense to add a third weak link to just-in-case solve an incredibly rare in-water problem (blown burst disk or massive leak of a tank neck o-ring)? Oh, and let's put it where its hard to get to, and set at a different orientation to every other valve.
I'm actually surprised that with the wide acceptance of sidemount (and the absolute aversion of the UDT sidemount isolator) that independent doubles haven't been widely adopted.
People go on and on about not adding failure points, but the weakest link in any valve is the handle and the serviable guts. So how does it make sense to add a third weak link to just-in-case solve an incredibly rare in-water problem (blown burst disk or massive leak of a tank neck o-ring)? Oh, and let's put it where its hard to get to, and set at a different orientation to every other valve.
I'm actually surprised that with the wide acceptance of sidemount (and the absolute aversion of the UDT sidemount isolator) that independent doubles haven't been widely adopted.