low pressure steel 125

[D1v1n]

What are differences I should be aware of between aluminum 80 or 100 vs low pressure steel 125? I have an opportunity to buy two of the low pressure tanks and they have never been used, but will need to be hydroed. I am trying to figure out all of the pros and cons, and I figured I could get some great insight. Thanks I look forward to reading the posts!

 

[mech]

Well you will probably end up getting several different tanks before you're done.
I personally don't care for aluminum...but that's just my choice because of the extra weight required on your belt and some might not be safe if they fall under certain numbers and dates.
The 125 might as well be considered a water heater but if the price was right I'd consider it...heck even jump at the chance if priced right.
I am very partial to steel tanks myself.

edited to add; could you swim up the 125 if you had a BC failure?
I won't dive double steels wet just for that reason.

Andy

 

[rushrhees]

You get less boyancy swings with steel tanks and again less weight on the belt. If you are an airguzzler the 125 CF will most likely allow you to stay under until your deco limit. Another thing to consider besides BC failure is how good your back is. when you have to walk with that tank on you it will put you lower back to the test.

 

[mweitz]

Ski,

To be more specific look at the buoyancy characteristics of all the tanks you are considering, as well as their actual weight and dimensions. Some tanks will be too long. If you are 5’4 an AL100 or Steel 125 will most likely be uncomfortably long and may cause you to have trim issues.

Here is a buoyancy example. A Luxfer 80 is 1.4 pounds negative full and 4.4 pounds positive when it is empty. You would have to wear an extra 6 pounds of lead to compensate for the swing from negative to positive. Steel tanks tend to start negative and stay negative through the dive. My 120's are 10.5 pounds negative full and 1.5 negative empty. What you should do is get the specs on all the tanks you are considering, then compare them in a spreadsheet or such.

Other things to consider would be the diameter of the tank. 7 ¼” diameter tanks are going to be a little easier to swim since they will have a bit less drag than 8” tanks. I wouldn’t use this as a deciding factor though…

Mark

 

[msandler]

they're a ***** on land but dive well. you can jam 160 cuft into them (spare me the flames...). If it gets too cumbersome, you can banish it to O2 service, get a transfill whip and pp blend your own trox (providing you can find a shop that will top-off)
if the price is right....
ps. get an H-valve

 

[Robert Phillips]

You get less boyancy swings with steel tanks and again less weight on the belt. If you are an airguzzler the 125 CF will most likely allow you to stay under until your deco limit. Another thing to consider besides BC failure is how good your back is. when you have to walk with that tank on you it will put you lower back to the test.

How do you figure you get less bouyancy swings? Air still wieghs the same regardless of its container. What you get is a tank that is closer to neutral or slightly negative when emtpy. My PST LP95 goes from -10.75lbs when full to -1.75lbs when empty. Thats a pretty large bouyancy swing. An aluminum goes from being negative when full to being positive when empty so you need more lead to counteract that. But 77.6 or so cubic feet of air still 6lbs or so of weight.
The reason you need less weight with steel is due to their bouyancy characteristics, not because of bouyancy swings.

 

[Soggy]

My back is hurting just thinking about LP125s....and I dive Double E8-130s!

 

[Don Burke]

What are differences I should be aware of between aluminum 80 or 100 vs low pressure steel 125? I have an opportunity to buy two of the low pressure tanks and they have never been used, but will need to be hydroed. I am trying to figure out all of the pros and cons, and I figured I could get some great insight. Thanks I look forward to reading the posts!

It has been a while since I used a 125, but as I recall, you will be wearing about four pounds less weight than with an AL80. Most divers can give up that much ditchable weight safely.

The full to empty change is going to be a bit larger, about nine pounds for the 125 as opposed to five point something for the 80. Your BC can probably deal with this just fine.

I got a pair of 112s, figuring I would double them at some point. Since I only use them as singles, a couple of 125s would have been a better choice.

 

[Tom Winters]

I love my 125's when I'm in the water, but damn they are heavy! Each one is 58 pounds when it's really jacked up full. They are a real pain to change out between dives on a pitching boat.
When you're figuring out the weight belt stuff, look at the empty tank buoyancy. My 125's weigh are exactly 1 billion pounds negative at the start of the dive, but neutral at the end. AL 80's are +4.4.
The 125's are real *******s to carry. They require a pretty bend of the elbow while you're lugging them, and loading them onto a boat requires some diligence. I've seen tank boots with wheels on them that could work, if they're not total junk.
My new favorite tanks though are the LP 85's I just snarfed up. They're lighter than an aluminum 80 but hold 129 cubic feet when they're fully loaded.
They're neutral too when they're empty.
With either steel tank and my steel backplate, I no longer need a weightbelt, and in the winter down here in Florida, I wear a 3/2 full over a 1mil full.

 

[D1v1n]

I am familiar with the regular k valves, my al 80's that I have came with them. I will have to buy valves for these tanks, what do you suggest for valves and why? A lot of people I know and msandler on scubaboard have said to get an h valve. The other question even if the tanks are hydroed and pass, should I be concerned about the age of the tanks, or because they are steel tanks, they are more durable, etc. The tanks themselves have never been used and still have packing in them. Thanks for all the input.