Buying my first tanks 15l (125) v 12l (100)

[Jerry_]

thanks for the help, i currently have 14 kg (28 lb) of weight with a 12.2 steel and my sac rate on the last dive was around 17. it's slowly improving i think it was around 20 at dive 12 and now i'm up to 18. 64 mins under for about 160 bar max depth was 8 m.

I suggest you to do regular buyoncy checks as you will see your need for weight probably decreasing, which will also impact on your SAC rate.

If you will always stay in a range not lower than 20m/60ft and within NDL, then a 12l would be fine. If you envisage deeper dives, then go for a 15l@232bar or 12l@300bar already now (some day you might even want to go for doubles, but that is some time ahead)

As mentioned in the previous post, do not expect your fill station to (always) provide you with a tank filled to its maximum capacity, so keep some margin, by having a higher-then-used capacity.

 

[mac.calder]

Most of the operators in Victoria are pretty good when it comes to fills... IIRC there is about a $70 difference between 15L and 12.2L when purchasing - I would consider putting the $70 towards purchasing a second 12.2L - check prices against these guys - they buy in bulk and will probably be cheaper than your LDS.

Quick fills are the enemy when it comes to getting a decent end pressure - a hot, fast fill (which if you are diving a fair bit will be what you get in the summer in Melbourne) may only be 180-190 bar (especially if you get the timid brand new instructor who does not know how to fill nicely) - If you have 2 tanks, drop one tank, they fill it & put it aside, you pick up the other, they top it up and away you go - if you are leaving a tank, there is no justification for a fill less than 220bar.

One tank is never enough - 2 MIGHT be enough - unless you do a lot of boat diving, in which case 4 is a better number.

 

[Coldspace]

I was like you. I opted for the 15 ltr as I am 180 cm and 105 kgs so wanted some capacity as well. I use the HLC large bcd which are great for this.

My smaller buddies use 12 lts and wife uses the 10.5 lts and we usually end up similar times down to 40 bar sometimes I am 20 bar higher. Better than always been the hadicapped guy on air over my buddy. This 15 ltr gives me more value out of my boat dives as well as the extra 15 mins comes in handy up here when we go out on 2 dive day and can get the tank filled on the boat for other dives. I probally buy another 15 ltr soon.
i don't find the extra weight any issue been a larger bloke. The 15 ltr is actually slightly shorter than the 12 ltr 232 bar just 1 inch fatter which I find sits better anyway on my oceanic probe straps.
having extra air is also good if in high current and you have to work abit.


Cheers

 

[Rhino1701]

Most of the operators in Victoria are pretty good when it comes to fills... IIRC there is about a $70 difference between 15L and 12.2L when purchasing - I would consider putting the $70 towards purchasing a second 12.2L - check prices against these guys - they buy in bulk and will probably be cheaper than your LDS.

i am going to buy from them as they have the best price i have found so far and i was intending to buy two as most of the time when we go diving it is either two shore or two boat dives. there is a $50 difference between the 15 L and 12.2.

eventually i hope to dive deeper as i am interested in wrecks but i'm in no rush yet, just thinking of future proofing my gear.

 

[fbk]

A bloke your size, I would definitely get the 15's. You can never have too much gas. I started with 12's, then twinned them up, so bought some 15's to replace them and never looked back. They are the same length just bigger diameter. Buoyancy wise there is very little difference, I dive with the same weight with either.

 

[FinnMom]

I already said that if I have to carry the weight one form or another, putting some of the weight into a bigger tank is nice.

But since it came up in later comments, I'd like to also point out that gas needs aren't always just about your needs, nor about your normal SAC rate.
If something goes wrong at the bottom part of a dive (even just 12-15m, let alone 15-18m) your gas needs are pretty darn high because
* both you and your buddy might need "your" gas from that moment on
* both of your SAC rates will jump maybe +100% or even more under sudden stress and might remain that high for the rest of the dive
* you two divers will need a minute, maybe 2 min at max depth (i.e. max gas consumption) to get calmed down and squared away for your air-sharing ascent

Also, because there are hugely more used 12L tanks out there, I also noticed that 15L retains more of its value in a resale.

 

[Pin83]

Rhino, I am a relatively similar size to you, and I only bought tanks when I started my DM training. I went for 15l Faber steels, and have never regretted it. I was conscious that, using smaller tanks, it was possible that I could be on the low side on an ascent, and that could pose a problem if someone else goes low and needs to share. This has since happened a few times, and it's not a problem because I usually have 100bar remaining on ascent with 15s...

The only downsides to larger tanks that spring to mind are cost (which is a minor difference), weight (but 15l steels are barely heavier than 12l alloys, and moving weight to your back is great!) and fitting into boat tank racks (this is a pain sometimes, no way around it...)
The old adage that you can never have too much gas remains true....

 

[Frosty]

Rhino-My STRONG recomendation to you is to rent some tanks and dive em before making any decisions re purchasing.
. In the last 6 weeks Ive been lucky enough to dive Al60 al80,10L steel ,12l steel and 15L steel
Every tank type feels different to dive with.
Im 80kg and 178cm. Diving tropical in a 3mm full suit I have 3.0kg and in a 7mm I use 7.5 kg as a baseline
I found the steel10l the "nicest" to dive with. The 15l feels big and cumbersome by comparison.
The way id describe it is that with the 10l I go where I want when I want -direction changes etc are quick and easy.
The 15 feels slow and ponderous when doing direction changes.It also seems to feel 'top heavy"
Im NOT for a second saying DONT buy a 15 but you might find with your ever decreasing(increasing??) Sac rate you are happy with 12l steels.
-Darn pity you aren't "over the ditch" I'd be happy to do a couple of easy dives with you and you could use one of my 15's and one 12

 

[Rhino1701]

-Darn pity you aren't "over the ditch" I'd be happy to do a couple of easy dives with you and you could use one of my 15's and one 12[/QUOTE]

Thanks so much for the offer, maybe one day I will be able to take you up on that offer.

I found out a friend has a 15 so I might ask to borrow it.

I like the idea of the extra safety the gas provides not only for me but for my buddies and so far diving with the 12's hasn't been too strenuous or presented any weight difficulties.

Thanks so much everyone for your help and advice.
cheers

 

[Frosty]

Rhino-I had to chuckle a little bit at your last post because Your mindset is EXACTLY the same as mine 3 years ago when I was in the same position as you.
I decided I needed the 15 so bought a 15 as my first tank.
Over here its yearly visual and biyearly hydro.
Now I have four 12's and two 15's. I just took my tanks in for their visual and realised one 15 still had its paper hydro cert on it -so it hasn't been dived in 12 months.
The only reason the other 15 had been used is I do a dive with my regular buddy then on our second dive we take one of the kids so not enough 12's .


PS-I agree with a poster above.You are still improving your sac rate and working on your weighting. I'll bet you will be amazed how much less gas you use once everything has settled down.