Transfilling Tank To Tank

[aw]

I'm wondering about something. In what situations would you every want to have a transfill whip with you in the field to transfill gasses from one tank (or set of doubles) to another? I'm confused about the applicability of this and why you'd do it. I know you could do a top off, but wouldn't that assume the supply tank(s) were large enough to manage a top off without requiring your fill tank(s) to be drained?

[FW]

I'm wondering about something. In what situations would you every want to have a transfill whip with you in the field to transfill gasses from one tank (or set of doubles) to another? I'm confused about the applicability of this and why you'd do it. I know you could do a top off, but wouldn't that assume the supply tank(s) were large enough to manage a top off without requiring your fill tank(s) to be drained?

I have a transfill whip, but hardly ever use it in the field. It might be useful to match your tanks to your buddies, though.

[Alan Owens]

When I did cavern and intro with "Y" valve 80's my instructor brought along a set of pumped up 104's to top our tanks between dives. We would remove the 1st stage without the SPG and he would fill the student's tanks to about the same pressure as each other. It did save us from having to bring along a bunch of singles.
Have a good time and a safe dive,
Alan

[crazyduck]

As an ex-instructor we used them most often between staff members towards the end of the day. Sounds silly but you get sick of paying $5.00 a fill from a site and having to wait in line for a single dive. You could top off a tank or level out two tanks between dives, never students. Students do not have a good grasp of how much gas they consume. Divemaster’s- well we’ll just say I have started too many dives (as a Divemaster) below 750 PSI. I used to dive with a training group that had 32 tanks. Divemasters were responsible for taking student empty tanks and marking the tank with the pressure. Newer Divemaster received tanks with more air (12-1500psi), experience divemasters grew gills (1000Psi and less.) (Please note this was OW instruction.)

I have found the most effective way is to have two or three tanks and you have a portable gas station. You use the tanks in order of pressure and step up the tank. You need the combination of size and enough pressure difference to work in your favor. So, if using Low Pressure steels you can use Aluminum tanks, or High Pressure Steel. That way you are maximizing the pressure difference.

All the usual rules apply for filling tanks. Careful around high O2 concentrations and mixes that are below 21% o2. If anything other than air is being used –test, test, test!

Recently, booster pumps have become more popular for moving pressure gradients between tanks. The problem is the cost – averaging $1500.00. However, for rebreather divers it can be worth while with the cost of pure oxygen and Helium.

Were they useful? When we are diving in the TransPasco Mountains and either you bring a portable compressor and O2 tanks (to make Nitrox) or you figure out something.
Another method is to get some high pressure K-tanks. Only down side is the weight- !

Andrew

[OneBrightGator]

It can be helpful to fill O2 or 50% bottles if you have an O2 "storage" bottle (72, AL80, whatever). I got my O2 topped off this past weekend that way, thanks John!

[curtschu]

But momma always said only studip question is one not asked.

How else do you fill your Deco O2 bottles off the big one.

Or are you not getting big O2 cylinders from the Gas Guys anymore.

[Kelly Jessop]

Comes in handy when you have different pressures in your sidemount tanks,and you can equalize before filling-this will keep your % close.

[Moonfuzzy]

I was once outside of cave country, somewhere that they only filled air, I used an extra deco bottle to fill my doubles for a nitrox mix.

[Kirk]

ok, this has nothing to do with cave diving, but when I do recreational dives, I use a transfill whip. I have two sets of doubles, a pair of PST 104s for cave and tech stuff and a pair of Faber steel 50s for recreational stuff. If I'm just doing shallow recreational diving, I fill up both sets of doubles, dive the steel 50s, and transfill off the 104s. I close the isolation manifold on the 104s, and thus have created a little cascade type system, draining off of one tank, then the other. I can get about 4 recreational dives off the 50s, and if I still want to dive some more, can get another one or two recreational dives off the very low preasure 104s. That's a lot of time in the water, for one trip to the dive shop.

[IowaCaveDiver]

we keep one on the boat we run off shore NC.... we'll usually grab a couple of nitrox 100's and then transfill our doubles between dives.... of course you won't have a full fill, but it is usually plenty of gas to do our second dive.... this provides a quick on the water fill with the same nitrox mix as we normally dive. I have also used the whip to transfill from a full bottle that I want to drain so as not to "waste" the gas.... my bosses get pissed when we have a full tank and then need to drain it for some reason, so even if I can dump a few hundred PSI into another tank, it makes them that much happier.

-Matt