OMSvs Faber

Since OMS tanks are made by Faber why do lp Faber tanks have positive buoyancy when empty while lp OMS tanks in the same 80-100 range claim to have neutral buoyancy. Some vendors claim there is no difference. This issue is important because I would like to drop some weight from belt.

Check the statistics for both low and high pressure tanks. The high pressure tanks will remain negatively bouyant when empty and the low pressure will reach neutral or even slightly positive depending of the size of the tank when empty.

Like wise the high pressure tanks will be lighter than the low pressure tanks. However the trade off is that getting fills may be harder, and it is harder on your first stage, shortening its service life and requireing rebuilds more often.

As an interesting note, the low pressure Faber tanks are plus rated to 2640 psi. But the service life is rated at 10000 fills at 4000 psi. Personaly after 10000 dives I could not care less if it fails a hydro, so I fill my LP Fabers to 3000 psi always. It adds over 20 percent to the volume from 2400 psi, and as we all know, bottom time is king!

90 cf @ 2400

99.9 cf @ 2640 ( a gain of 11 percent for plus rated tanks)

108 cf @ 3000 ( a gain of 20 percent from 2400)

take an OMS 98 and a faber 95... same size (exactly same specs) same pressure, same manufacturer, one is 98 cuft the other is 95 cuft... huh?

You need to be careful when making comparisons. As the previous poster noted, same tank ... different volume rating. That's because Faber and OMS use different algorithms for calculating the volume ("voodoo math" for marketing purposes). In reality, at the same pressure, you've got the same amount of air in both tanks, regardless of what's stamped on the crown.

As to the buoyancy, some distributors (e.g. OMS or ScubaPro) rate the buoyancy with a valve, while others (e.g. Faber & PST) don't. Not that anyone would ever dive a tank without a valve, mind you. The reason the former does this is because although the tanks may be the same, they use their own valves on the tanks they sell.

So making direct comparisons can be misleading.

BTW - I'm not aware of any steel tanks that are positively buoyant when empty. My Faber LP95s, with valve, are approximately 2.3 lbs negative when empty. My MP72's, when empty, are about 5.5 lbs negative.

... Bob (Grateful Diver)