LP or HP tank?

[Raiderswim]

I am looking to extend my air supply for deeper rec limit dives.  Looking for a steel 130.

Question is LP or HP?  What are the pros and cons of each besides physical size?  What do you tech guys use?  Again just looking for that little bit of extra air for the deeper dives.

Thanks

[Vtach]

If you are strictly looking for a single steel cylinder, you probably won't find a whole lot that have 130 cu ft at low pressure (2400).  The largest LP cylinder that is readily available are the 120's.  That leaves you only HP if you are dead set on 130 cu ft.  I prefer doubles and would recommend that you also have redundant regulators (1st and 2nd stages) if you are looking to extend your range and time safely for either doubles or a single.  Small size doubles like 72's or 80's are great for a start.  They are also reasonably priced and you might just find a used set of small doubles cheaper than a single new LP 120 or HP 130.

I guess the biggest things you may want to consider is exactly what depths you are planning, what your gas consumption rate is.  Once you have those things calculated you can run some mock dives and see what your gas needs are to safely complete the dive.  Based on that information, you may only need a stage or you might need double 130's AND a stage ;D.

Here's a link to help anyone out with calc's.

[Vtach]

LP are usually bigger and heavier (for the same comparable volume as HP) but if you have your own fill station or find a willing dive shop, you can overfill them and get a good amount of extra gas.  The larger size LP cylinders do not work well in jacket style BC's, they are tall, heavy and cumbersome.

HP you rarely will get a fill that will maximize the full potential of what the cylinder is rated for.  Most cases you will find they will cool down to below the rated pressure.  I don't see too many downsides other than that.