Scuba tank=compressed air

[viperx1_1000]

Ok, I have a gun that only runs on nitrogen or compressed air. I live 200 miles away from the nearest pro-shop. I do have a diving store. I was thinking about renting a tank and buying a fill station, there is just one question i had that no one has seemed to answer. If you refill your hpa bottle multiple times from the same tank the overall pressure is going to go down right? That would mean you could get about one true fill out of it before it dropped down in pressure. Is this true? Please, someone correct me if i'm wrong.

[vf-xx]

Ok, I have a gun that only runs on nitrogen or compressed air. I live 200 miles away from the nearest pro-shop. I do have a diving store. I was thinking about renting a tank and buying a fill station, there is just one question i had that no one has seemed to answer. If you refill your hpa bottle multiple times from the same tank the overall pressure is going to go down right? That would mean you could get about one true fill out of it before it dropped down in pressure. Is this true? Please, someone correct me if i'm wrong.

I get fills from the local scuba station and I've generally foudn that I NEVER get full fills. It works for me because usually I only need a little bit to do some testing or sumsuch. It really depends on what your scuba store fills to. Mine typically fills to 2200~2500 psi. This means that I can usually get two or three fills above 2000psi, but I also have a large tank.

To directly answer your question, yes after you fill the first time the overall pressure in the scuba tank drops some. However due to differences in volume, the pressure in the scuba tank will drop much slower than your HPA tank fills.

Hope that helps.

[Flossabe]

We just switched to using scuba tanks for our air, we got tired of paying 4.50 for a 68/3000 fill. We get ours filled to 3000 from the scuba shop and off of one 80 cft tank we can get approx 6-10 fills above 2000 psi, but after that we fill our tanks up from 0 to whatever the low scuba tank is and then fill the high pressure off of a fresh tank, this works with the pressure volume formula to make more efficent use of pressure, but look to spend any where from 130 to 200 for a tank setup with a fill station if you dont have a tank alredy.

[JimmyBeam]

what does the scuba shop charge to refill a tank? im thinking bout getting a pony tank myself

[Mister Sinister]

For whats its worth the setup I use is a 120 c.f. Pressed Steel scuba tank. Its much larger than the stardard 80 c.f. aluminum tanks that are sold. The Pst tanks are also rated at 3500 psi instead of 3000. With this set up most of the time I get about 3100 to 3200 psi in my tank when I get it filled. I've never kept track so I dont know exactly what the drop off rate in the pressure is per fill. I would venture to guess that I get at least 16 or so before the tank hits 2000 psi. I know its enough for my brother and I to play all day on. The only draw back to these tanks is that they are much more expensive hitting in the 300 dollar range.

[Flossabe]

It costs me between $4.00 and $5.00 for an 80cft tank, im not sure if the larger or smaller tanks are more or less just depends on the shop but not bad prices at all.

[deadeye9]

The exact pressure decrease is calculated at:

http://www.automags.org/forums/showthread.php?t=132980

go to the last post by athomas. An 80 cf scuba tank should be enough to get you through the whole day.

[Major Jam]

I use two 3000psi 80c.f. aluminum scuba tanks. One to fill and the second to top off.

I can usually get my local shop to cold fill them to 3100psi. It costs me $8 to fill two tanks.

At the field, the first fill is about 3000psi, the second fill is about 2900, third is about 2800 fourth is about 2700, etc.

It's more of a pain though because I only have one fill station right now to move between tanks. Plus it is was a little more expensive buying two scuba tanks. But, I think I get more, higher pressure fills that way.

[PzYcO]

Personally ive got a 120cuf 3500psi scuba tank which i fill to 3500psi on my 4500psi compressor, which i use to top 4500 tanks off.. Tank @ 300$/Compressor (w/ new motor) @ 2000$/Fittings @100$