Steel 117 vs 120

[eweingarden]

I'm looking to get another steel tank (I have a steel 100) and am considering a 117 and 120. I see that the 117 has a diameter of 8" whereas the 100 is 7.25". The tank band on my setup is not easy to adjust. Would the 3/4" larger diameter of the 117 require the band to be adjusted each time I switch tanks?

Is there some reason to use a 117 instead of a 120 since the volumes are almost equivalent? Thanks.

 

[guruboy]

Yes

The 117 is shorter and wider than the 120. Might matter depending on your height.

 

[2airishuman]

I'm looking to get another steel tank (I have a steel 100) and am considering a 117 and 120. I see that the 117 has a diameter of 8" whereas the 100 is 7.25". The tank band on my setup is not easy to adjust. Would the 3/4" larger diameter of the 117 require the band to be adjusted each time I switch tanks?

As posted upthread, yes, you would have to adjust the cam bands when switching back and forth.

Also, 8" cylinders frequently do not fit in the cylinder racks on charter boats, so you have to keep them under the benches, which is a nuisance, albeit a minor one.

Is there some reason to use a 117 instead of a 120 since the volumes are almost equivalent? Thanks.

The 120 is too tall for some divers. I'm 6'1 and 120s work great for me.

 

[ScubaSteve85]

Most folks will probably recommend the 120 since it's the same diameter as your HP100s, and for a while I was super gung-ho on buying one...until I actually tried one. I'm 5'10, athletic build, and I found that I trim out much better with the 117 than the 120. It made a surprisingly large difference. My suggestion would be to rent a 120 first to make sure it works for you.

 

[tbone1004]

@ScubaSteve85 you're just too short for a 120, nothing you can really do about that. They're really long. AL80's are probably a hair on the too long side for you as well. They really aren't ideal for anyone less than about 6' tall. HP100's or LP72's are much better tanks

My quite firm opinion on scuba tanks is that they should always be bought in pairs with the exception being deco bottles
Reason for that is if you have a 2 dive day planned, which most people do, everything is going to be the same equipment wise between those two dives. Buoyancy does change between most tanks, so it's quite difficult to have a tank that won't cause changes when you switch.
With this, you also remove the option of potentially putting those tanks into doubles or sidemount when you have them mismatched which is why I am adamant about not buying individual tanks for myself. The only single tanks I have are an AL30 and an AL40 both of which were given to me and are used for deco, everything else has a mate.

With the 117 you add the extra inconvenience of adjusting the cam bands each time you switch tanks unless you are in a BP/W with an STA and then have an extra STA for that tank. I dive with several guys that swap their wing and plate over to different tanks and the tanks have semi-permanently mounted STA's on them.

 

[eweingarden]

Thanks for the feedback.

 

[DoubleAA]

I have a pair of 117's and have had 120's as well (and 133 and a myriad of other tanks). Adjusting the cam bands takes a couple seconds for me, I travel with the same setup and haven't really noticed the 30 seconds it takes me to adjust a couple cam bands causing me any grief. I've also never had trouble on a charter in NC/SC/FL with my tanks. Usually my 8" bottles stay put in the rack much better than some of the taller skinnier 120's.

Get the tanks that fit you and trim out the best.

 

[Trailboss123]

Agree with @tbone1004 - If it were me, I'd get another Steel 100 to pair with the one you already have.

 

[guruboy]

Agree with @tbone1004 - If it were me, I'd get another Steel 100 to pair with the one you already have.

That is actually NOT what @tbone1004 is advocating, as that would be buying two tanks at two different times.

 

[eweingarden]

Although I have no plans of doing doubles, I think I'll go with another 100.