How often do you actually get a full tank fill?

[rhwestfall]

[P(1)*V(1)]/T(1) = [P(2)*V(2)]/T(2)

The shops after tens of thousands of fills, should have it modestly figured out....

 

[TravisD]

In my experience, fill quality is related to how much of a rush you're in. Showing up 10 minutes before closing top and expecting to take your cylinders home on the same trip is more likely to result in a short fill than if you are able to drop them off and pick them up when the operator says they'll have them ready.

Heck - this applies even when I'm doing my own fills. When I plan ahead and start filling a few days before the dive I can do the initial fill, let them cool off, then top off. When I realize that I forgot to fill the cylinders that I want to take with me, the fill is going to be faster and maybe a little hotter.

On my last Florida trip, the fills I got there were great! Notably the shop not only had me analyze and record my Nitrox F02, but also the pressure as well, which to me speaks that they don't want anyone to come back (or post online) complaining about a short fill.

One situation where I've seen the most short fills has been when someone rents a cylinder, and the shop just grabs one out of the "full" rack without checking. Cause could be a leaky valve (maybe slow enough that it's not noticed when in regular use but apparent after sitting a while), or perhaps someone borrowed one "just to test someting" and put it back in the full section, or maybe it was just short filled. In any case, checking before leaving the shop would have caught it.

 

[chthonicly]

As the proud new owner of a beautiful 100 HP steel tank I'm looking back on my rental days, and just about never was it filled to spec. Of course, once in the cold water the psi would droop ever lower.

For more experienced tank owners, how often does your tank actually get filled to spec? With adiabatic heating during the fill process the internal PSI will only drop as it reaches ambient temperature.

Is the rule of thumb to buy a 100 when you need 90 cubic feet, and a 120 when you need 100?

"full" is very regional/situation specific.

In SoCal you should have access to shops who will give you a HP fill. Not all of them do, as some of them only have compressors which go to 3k -- on the SoCal boats you will only get 3k if they even have a compressor. Also, if you need nitrox and their banks are low, they might give you a lower pressure fill. To avoid this, try to get fills during the week or earlier in the day. This is one of the reasons why a lot of folks have many tanks.

I usually get a ~3.5k fill on hp100s in NorCal. in 50 degree water, this usually ends up with 3.3k actual on the gauge in the cold water. YMMV a lot.

When I got fills in Florida it was not uncommon to leave the shop at ~3.8k and be in the water with 3.6k.

 

[TMurrr]

All depends on the shop. I had a 100 card fill card at the first "LDS" - terrible for HP fills. I don't think I EVER got to 3442 psi without explicitly complaining. Yet the store owner was very confused when I told him I was taking my business up the street...

Now I go to a high volume, very reputable shop and have 0 issues getting a full HP fill of banked EANx.

 

[Jcp2]

I go to a shop with water bath and always get a good fill on my HP100, usually 3500-3600. They are even kind enough to fill my non plus LP72 to 2400-2500. Since a lot of my regular dive group members use AL80, I use a transfill whip to make 80’s out of the 100 and 72.

 

[landphil]

I get about half of my HP steel fills around 3400 at a place that does nonstop HP water bath fills all day. Weekend peak traffic fills usually and up closer to 3200. Slow weekday fills occasionally get towards 3600. And my closest shop will land your tank somewhere between 2900 and 4000 PSI, filled with something between EAN 28 and EAN 40 if you’re going nitrox. But I only go there when I really need a quick fill.

 

[Divin'Papaw]

I get about half of my HP steel fills around 3400 at a place that does nonstop HP water bath fills all day. Weekend peak traffic fills usually and up closer to 3200. Slow weekday fills occasionally get towards 3600. And my closest shop will land your tank somewhere between 2900 and 4000 PSI, filled with something between EAN 28 and EAN 40 if you’re going nitrox. But I only go there when I really need a quick fill.

Dang!!! I better start really appreciating my 3600-3800 fills in 15-20 minutes typically with EAN at +- 1% of requested mix. Didn’t realize how good we have it in South Florida.

 

[Pi_grim]

Here in the N Texas area the dive shops act like they’re doing me a favor by taking my $$ and giving short fills.
Florida shops are great and yeah, ya’ll don’t know how good you’ve got it over there!

 

[Jollymon32]

I have a regular staff member that I visit at a LDS. I tip him religiously. I leave with 4K most of the time 3.8K at peak fill times. Cheaper than getting my own compressor to top off.

 

[Eric Sedletzky]

Getting a cave fill here is very difficult to obtain.
My shop is pretty good though, I get 2500 in my LP72's and a full 3500-3600 (when cold) in 3442's so I can't bitch too much.
I got four grand once in my 120 and danced all the way to the dive site.
It helps to pick them up later and request that they get "topped up".
Other than finding a shop that gets it, the other alternative is to buy your own compressor.