When to buy tanks?
- Thread starter openhelix
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Clammy
Contributor
Mine certainly does. x_X
I know mine already does
... and Heaven help me if the LDS has a sale on HP130's :shocked2:
rstofer
Contributor
Just work it out roughly based on what you get out of an Al 80
Absolutely! You need 4# of weight to sink the Al 80 tank that's 4# positive at the end of the dive. That's just what you are wearing. So, basically, other than the tank, you are neutral. An HP 100 is 2.5# negative at the end of the dive and 10.5# negative at the start of the dive. So, if you don't wear any weight at all, you will still be around 2.5# negative at the end of the dive. Worse, you won't be wearing any ditchable weight so rescue will be more complicated.
NDLs are what they are. If you dive deep, you can't stay long. One answer to staying a little longer is to use Nitrox. It can dramatically increase your allowable bottom time.
Richard
rollerboi
Contributor
I need a new credit card that the wife doesn't know about. 
OP
I need a new credit card that the wife doesn't know about.
Agreed! I did the math today and figuring the difference between renting tanks and just a fill (of your own tanks) is around $7/tank/day. That means at roughly $700 for two HP100s/120s. Figuring 2 dives per day locally, 2 days diving per "trip" that's 4 "fills" per trip saving $28/trip. $700/$28 means tanks pay for themselves in roughly 25 trips... Given I'm <90min from Monterey that's not unreasonable in a year or less.
So, the financials make a lot more sense than I thought... Now to convince my LDS to give me free fills for buying tanks from them and cut that ROI number!
TaoH
Contributor
I bought a pair of Worthington HP100s about 2 years ago from Any Water Sports in San Jose and they gave me a free air fill card per tank (that means 2 air fill cards). I'm not sure if they would have given me a Nitrox card as I wasn't certified for it at the time and didn't want to play with Nitrox when I didn't know everything about it. Each fill card comes with 10 fills.
I bought them on a whim because I was actually going to rent a pair of HP100s for a weekend. Having rented tanks so many times in the preceding months of buying them, I was able to try Steel 72, 80, 95; HP 80, 100. After going through that many tanks, I found that I liked the HP80s for being compact and lightweight and for leisure paced dives, it was enough air to finish a dive with several hundred PSI left on a proper fill. The HP100 gives me extended bottom time and it doesn't bother me so much to use a slightly larger tank; I'm often left with 1200~1400PSI of air at the end of a leisure dive unless I take a faster pace, dive solo, or dive with someone that has similar SAC rates. On a short fill or when filling from a station that doesn't support HP pressures, I should still have at least 79+ cu-ft of air; close enough to the 80 for the typical dive whereas the HP80 would have about ~65 cu-ft on the LP fill (I've forgotten what my calculations concluded).
I also liked not having to rush to the shop to pickup and return tanks around a weekend. It's not very convenient as I have to wait for the shop to open before the beginning of the weekend and then rush to the shop after work on Mondays before they close to make it before being overdue.
I bought them on a whim because I was actually going to rent a pair of HP100s for a weekend. Having rented tanks so many times in the preceding months of buying them, I was able to try Steel 72, 80, 95; HP 80, 100. After going through that many tanks, I found that I liked the HP80s for being compact and lightweight and for leisure paced dives, it was enough air to finish a dive with several hundred PSI left on a proper fill. The HP100 gives me extended bottom time and it doesn't bother me so much to use a slightly larger tank; I'm often left with 1200~1400PSI of air at the end of a leisure dive unless I take a faster pace, dive solo, or dive with someone that has similar SAC rates. On a short fill or when filling from a station that doesn't support HP pressures, I should still have at least 79+ cu-ft of air; close enough to the 80 for the typical dive whereas the HP80 would have about ~65 cu-ft on the LP fill (I've forgotten what my calculations concluded).
I also liked not having to rush to the shop to pickup and return tanks around a weekend. It's not very convenient as I have to wait for the shop to open before the beginning of the weekend and then rush to the shop after work on Mondays before they close to make it before being overdue.
halocline
Contributor
This is an absolutely false statement. First, you have no way of determining what would or would not "complicate" any particular rescue scenario. Second, typical rescue procedures (well, PADI) for an unconscious diver at depth are to not ditch weights unless the victim is so overweighted that you can't get him/her off the bottom. This would not apply to properly weighted divers. Ditching weights is for the surface.
The statement is also misleading in that it implies that not diving with ditchable weights is unsafe. This is simply not true. Accidental weight loss at depth is common, and that's an increased risk of ditchable weight. You have to balance that with whatever risk of not being able to easily get positive at the surface is increased by not having ditchable weights.
It's a far more complex issue that to just say "no ditchable weights complicates rescue."
rstofer
Contributor
Any way you cut it, the first step upon surfacing is to get the victim positively buoyant. There are a number of possibilities but ditching their weight is preferred because it is fast. If the victim doesn't have ditchable weight, some other method is required. One might be to ditch the rig. But that means the victim, if still breathing, won't be breathing from their regulator. Maybe air sharing works but ditching the rig eliminates the tank tow. Maybe their BC/wing still works - who knows? I consider this complicating the rescue.
I don't think I mentioned ditching weights at depth although that could be required. That isn't usually done but there is the possibility that a single wing won't lift two divers off the bottom. My 30# wing is just such a device. I wear 20# of weight, 6# backplate and my tank is 10# negative at the start of the dive I must have 6# of lift in my compressed wetsuit or I have to swim it up. However, should a victim have a similar configuration and a blown wing, there is no way I can lift them off the bottom. Unless there is a way to ditch something, one of us isn't coming up. A self-rescue without a lift bag or SMB might be out of the question. Even ditching 20# of weight would still leave me 10# negative on the bottom - if I have 6# of lift from my wetsuit.
All in, I am a fan of ditchable weight even to the extent of adding foam flotation to the rig to force the requirement. I was taught that ditchable weight is a good thing and I still believe it. I suggest that every diver look at their tank buoyancy and weighting and then think in terms of getting positive at the surface without a bladder. This will be difficult for warm water divers with steel tanks and trivial for cold water wetsuit divers using a single tank. Doubles present another issue...
Richard
I don't think I mentioned ditching weights at depth although that could be required. That isn't usually done but there is the possibility that a single wing won't lift two divers off the bottom. My 30# wing is just such a device. I wear 20# of weight, 6# backplate and my tank is 10# negative at the start of the dive I must have 6# of lift in my compressed wetsuit or I have to swim it up. However, should a victim have a similar configuration and a blown wing, there is no way I can lift them off the bottom. Unless there is a way to ditch something, one of us isn't coming up. A self-rescue without a lift bag or SMB might be out of the question. Even ditching 20# of weight would still leave me 10# negative on the bottom - if I have 6# of lift from my wetsuit.
All in, I am a fan of ditchable weight even to the extent of adding foam flotation to the rig to force the requirement. I was taught that ditchable weight is a good thing and I still believe it. I suggest that every diver look at their tank buoyancy and weighting and then think in terms of getting positive at the surface without a bladder. This will be difficult for warm water divers with steel tanks and trivial for cold water wetsuit divers using a single tank. Doubles present another issue...
Richard
jlw
Registered
I bought my tanks because they suited my style of diving and gave me a consistency in weighting and equipment that I didn't get with rental tanks. I bought a Steel 78 over 10 years ago. Its great and let me take some weight out of my pockets. I didn't have the issue of different AL80s coming at me with each rental. Fills were free on the boats, for the most part, and I'd take 1 tank of air with me. I did a lot more shore diving and the 78 was a good size.
Now I do a lot more boat diving and a BP + HP100 get a lot more weight out of my pockets and into a better place on my back. I've as much to more air and while that doesn't mean I stay down longer, it means i come back with a huge 1100-1400psi margin for error.
Now I do a lot more boat diving and a BP + HP100 get a lot more weight out of my pockets and into a better place on my back. I've as much to more air and while that doesn't mean I stay down longer, it means i come back with a huge 1100-1400psi margin for error.
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