Not being a twin set diver this question comes from ignorance of the configuration. Why is the manifold necessary? Couldn’t you have two independent tanks just like sidemount but mounted on the back? I’ve seen videos of valve shutdown drills and it seems like an unnecessary step to close the isolator valve prior to closing the affected tank. Is it because you can’t see the valves to determine which is compromised? I would think one could just reg switch just like sidemount but in backmount configuration.
Hi Tony, if you are diving independent cylinders then better, they are not on the back and in sidemount most agree with this. So if they are on the back, then yes the isolator manifold makes sense. How it used, we do talk about this in some of our videos give this one a watch in the backmount course https://www.sidemounting.com/lesson/valve-shutdown-exercise-twinset-5-min/. In any gas failure with a twinset, you cannot see the valves and you do not rely on your teammate to fix the initial problem, the divers always breathes the long hose which is on the right-side post behind your head and on the left side post you have the only SPG. So, in event of problem, you want to close the isolator as fast as possible this way it saves the gas in one of the twinset cylinders, the gas in the other might be lost for good depending on the actual failure. Once isolator is closed you check the SPG if needle is moving or empty you know failure is on the left cylinder (behind you) if your long hose regulator is having a problem, you know it is the right cylinder (behind you) with the problem then you switch onto the other regulator which is on a short hose coming off the left cylinder, you continue with this. If problem was with either 1st stage connection (burst disk or manifold leak) then you have isolated it and saved half your gas, if problem is with something after the 1st stage (free flowing regulator, that cannot be stopped), then you can close that cylinder off and re-open the isolator and able to gain the remaining gas from both cylinders. Hope that helps you understand a bit more, sidemount and independent cylinders do give you additional redundancy, but it is important to note manifold failures are extremely rare. Regards, Steve
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Steve/Vas,
Not being a twin set diver this question comes from ignorance of the configuration. Why is the manifold necessary? Couldn’t you have two independent tanks just like sidemount but mounted on the back? I’ve seen videos of valve shutdown drills and it seems like an unnecessary step to close the isolator valve prior to closing the affected tank. Is it because you can’t see the valves to determine which is compromised? I would think one could just reg switch just like sidemount but in backmount configuration.
Hi Tony, if you are diving independent cylinders then better, they are not on the back and in sidemount most agree with this. So if they are on the back, then yes the isolator manifold makes sense. How it used, we do talk about this in some of our videos give this one a watch in the backmount course https://www.sidemounting.com/lesson/valve-shutdown-exercise-twinset-5-min/. In any gas failure with a twinset, you cannot see the valves and you do not rely on your teammate to fix the initial problem, the divers always breathes the long hose which is on the right-side post behind your head and on the left side post you have the only SPG. So, in event of problem, you want to close the isolator as fast as possible this way it saves the gas in one of the twinset cylinders, the gas in the other might be lost for good depending on the actual failure. Once isolator is closed you check the SPG if needle is moving or empty you know failure is on the left cylinder (behind you) if your long hose regulator is having a problem, you know it is the right cylinder (behind you) with the problem then you switch onto the other regulator which is on a short hose coming off the left cylinder, you continue with this. If problem was with either 1st stage connection (burst disk or manifold leak) then you have isolated it and saved half your gas, if problem is with something after the 1st stage (free flowing regulator, that cannot be stopped), then you can close that cylinder off and re-open the isolator and able to gain the remaining gas from both cylinders. Hope that helps you understand a bit more, sidemount and independent cylinders do give you additional redundancy, but it is important to note manifold failures are extremely rare. Regards, Steve