LP vs HP decision

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Rob9000

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Scuba Instructor
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San Francisco Bay Area - East Bay
I rent tanks and am looking to own....partly for convenience and partly to ensure I can get larger capacity without having to call around and go out of my way. My first stage is not set up for DIN. I am able to get HP fills around where I live and would be diving. The diving would be single tank in a shell dry suit with a bp/w. Some questions:
- HP w/o DIN.....will I be blowing o-rings left and right, or is it not that big a deal?

- HP, LP and fills - I understand HP tanks have to be filled at a slower rate - is this enough of an inconvenience to drive people to LP? With a LP with a + rating, does this mean you are more likely to get a fill that will settle to the "full" pressure as compared to HP if you are trying to get a mid-day fill at a shop near a dive site to do another dive? So...if you have just one tank, does that change the game in terms of what kind of tank to buy as compared to if you have enough tanks for a day of diving w/o refills ?

- Tank dimensions and trim - I assume a longer tank will have different trim characteristics than a shorter one...as in a longer tank means a longer lever pulling on the fulcrum point of where the tank is strapped to the backplate or BC. I am tall - does that automatically mean look for a longer tank? How much should diameter and length be a factor for me, and if it is a factor then what are some things I should be paying attention to in upcoming dives to help me decide? I guess an alternative questions is: since I am tall, then does that mean that a longer tank will not impart as much trim characteristics of its own?

Other things I should be considering?
 
Man,,, it has been covered so many many times on the board..


Search is your good friend...:wink:
 
:search: Then ask specific questions. Usually works best.
 
Ok, I'll tell you my experience (without searching). I have a HP 120, and 2 LP85s. Unless I let the HP cool for at least 30 minutes then have it topped off, I get a light fill. Usually in the 3200 range. But with my 85's, I get them somewhat overfilled, so I always end up with at least a full tank. Usually a little more.

I have the convertable valves that have an insert to convert them from din to yoke. When I've used a yoke regulator, I haven't had any O-rings blow. But to be fair, I rarely use my 120 with a yoke reg.
 
I did search, but the questions and answers are not as specific as what I am asking...like people make recommendations for a specific person or situation w/o telling why. Many of the other posts are asking about preference between two different sizes of HP tanks. It would be nice if some people could get together and write the definitive guide and sticky it. That is why I like the idea of Wikis rather than forums for organizing this kind of info, but that is another topic. I did just find this link on DiveRiteExpress's web site about choosing a tank...this helps narrow it down for me: http://www.diveriteexpress.com/library/tanks.shtml
 
Rob9000:
I did search, but the questions and answers are not as specific as what I am asking...like people make recommendations for a specific person or situation w/o telling why. Many of the other posts are asking about preference between two different sizes of HP tanks. It would be nice if some people could get together and write the definitive guide and sticky it. That is why I like the idea of Wikis rather than forums for organizing this kind of info, but that is another topic. I did just find this link on DiveRiteExpress's web site about choosing a tank...this helps narrow it down for me: http://www.diveriteexpress.com/library/tanks.shtml


Ok... I will bite...

You have already answered your own question. There is no one right answer on that debate.


Depending on your air fill environment,
your type of diving, and
your body characteristic, such as weight, height, and so on.

The answer will be different and there are so many different opinions that have been addressed so many times.

HP w/o DIN.....will I be blowing o-rings left and right, or is it not that big a deal?

Yes/No. If you put the air more than 3442 psi, O-ring for Yoke doesn't last long. Check out my photo gallery. You can see some O-ring rupture after filling up to 4000psi.


- HP, LP and fills - I understand HP tanks have to be filled at a slower rate - is this enough of an inconvenience to drive people to LP? With a LP with a + rating, does this mean you are more likely to get a fill that will settle to the "full" pressure as compared to HP if you are trying to get a mid-day fill at a shop near a dive site to do another dive? So...if you have just one tank, does that change the game in terms of what kind of tank to buy as compared to if you have enough tanks for a day of diving w/o refills ?

Depending on your air fill environment. They don't mind overfill? If then, any tanks will be fine. What you want is a right fill. The heat issue applies to any tanks (HP/LP) because most tanks are filled from the bank.


- Tank dimensions and trim - I assume a longer tank will have different trim characteristics than a shorter one...as in a longer tank means a longer lever pulling on the fulcrum point of where the tank is strapped to the backplate or BC. I am tall - does that automatically mean look for a longer tank? How much should diameter and length be a factor for me, and if it is a factor then what are some things I should be paying attention to in upcoming dives to help me decide? I guess an alternative questions is: since I am tall, then does that mean that a longer tank will not impart as much trim characteristics of its own?

If you are tall, a longer tank will be a good option. However, you have to dive it first to figure out exactly what fits to you. This question applies to your LP/HP selection as well.


What kind of an exposure suit do you plan to use? How many weight do you need at this moment?


Other things I should be considering?

Search... Search..... Search.....


I hope it helps.
 
Rob9000:
Other things I should be considering?

If you are diving wet or dry. LP tanks are generally much more negatively bouyant than HPs.
 
Rob9000:
The diving would be single tank in a shell dry suit with a bp/w.

He said he'll be diving a dry suit...

Answer to ALL your problems: HP Steel 130 CF!!! :D
 
https://www.shearwater.com/products/teric/

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