How Much Would I Lose?

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brawler1588

brawler1588

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Sep 15, 2015
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Mahopac, NY, United States
So I took my scba tank to the dive shop for a fill and they asked me to leave the tank so they can top it off after it cools off. If I just took it after they filled without a top off how much would I really lose the dive shop is 35 minutes away one way and really don't want to have to go back the next day. I did it this time bit im curious. Thank you in advance 
 
I agree with Tom's figures on pressure loss. In the beginning when I would get my 60 minute SCBA tanks filled at my dive shop, I'd see almost a 400psi short if the shop didn't let the tank cool off and then top back up. 2 instances of that at $25 each and I stopped using the dive shop for 4500psi fills and went down the giant rabbit hole of having my own compressor to fill tanks. Now when I fill my own tanks, I'll usually see 250-300psi drop after letting the tanks cool. I "lose" less air when filling with the compressor compared to dive shop fills because the shops are usually filling our tanks from their holding tanks which is faster than if you were to pump it with a compressor. The faster the fill, the hotter it gets, and more susceptible to pressure drop once the bottle cools. 
 
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Tom is right. Anywhere between 200 to 500 PSI. I always have my SCBA tank filled at a dive shop. If they are busy, they might not be willing to take the time to fill it slow. There's only a few times where I've had my SCBA tank filled to 4500 PSI and the pressure stabilized and that's because I would wait for it. 

I've also had them slow fill it to 4700/4800 PSI and my tank would settle at 4500. I want my own compressor but I'm not willing to settle for a cheap Chinese brand. For now, paying $3.00 at the dive shop works out fine for me and it ain't bad because it's only a five minute drive from my house. 
 
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It's a 60 minute scba tank, is it worth the wait you think for the top off?
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I would say it's definitely worth the wait to have them cool the tank and top it off. There's a pretty noticable difference in the number of times you can fill up your rifle from a 4500psi tank compared to like 4100.

AoA has a "Tank Fill Calculator" on their website that you can use to get an idea of what that impact would be on you and whatever particular airgun you're filling.
 
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In my area, the places that provide paintball tank fills won't touch any tanks as large as the 30/45/60 minute SCBAs we use. They only deal with 45-108 cu. in. tanks unfortunately.

At this point, I'm fully committed to filling my own tanks mainly because of how much money I have sunk into my Yong Heng compressor. Your right, and while the compressor is about $250ish, you'll probably end up spending at least $125-150 on a moisture filter, compressor oil and just misc stuff. IMO, some kind of moisture filtration beyond what the compressor ships with is a must, or you're going to have lots of moisture in your tanks. That's one of the benefits of using a shop for fills, their compressed air goes through a dryer. It's disgusting to think about it, but I'm probably close to $800 spent on my Yong Heng compressor setup. It's definitely not typical for YH owners to spend that much on their setup, but I've added/modified/replaced a lot of stuff on my compressor. I have 2 stages of moisture filtration, upgraded hoses/fittings/pressure gauge, and I keep a bunch of spare parts around for most any type of failure a Yong Heng compressor might have. I hate waiting 30 days for parts to arrive from China, especially if it means I can't run the compressor until a part arrives.


 
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So I took my scba tank to the dive shop for a fill and they asked me to leave the tank so they can top it off after it cools off. If I just took it after they filled without a top off how much would I really lose the dive shop is 35 minutes away one way and really don't want to have to go back the next day. I did it this time bit im curious. Thank you in advance
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I have a 3300 psi tank that the shop usually fills up to 3600 psi.

My local Dive Shop usually takes about 20 - 30 mins to fill it up from 2500 psi - 3600 psi as the (usually) fill it up slowly, with breaks in between, to accommodate for the heat-related pressure loss.



But, last time I was in there - it was 15 mins to close - and the chap working (probably didn't want to stay past closing time) did the whole thing in less than 10 mins.

(When I asked him how much he'd charged it to - he said the usual ... Which meant 3600 psi)



When I came home and plugged in my pressure-gauge, to charge my Impact, is when I realized that the tank only had 3100 psi in it.

Now, I can't for certain say the heat-related pressure loss is what caused a 500 psi drop - since it's very possible that the kid was in a hurry and stopped at 3300 psi.



But, since that experience - I always go in the morning - so they don't have any incentives/reason to do a shoddy rush job ! :) 
 
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