On Saturday, Dec 20, 2003, at 13:47 US/Pacific, Peter L. Peres wrote:

> I have heard of, and have recommended to others, using a scuba
> air tank for this, with a very small window.
    :
>  It is also easy to test if you have a boat

Why do you say that?  most scuba tanks are very close to
neutrally boyant; they sink SLIGHTLY when full, and float
SLIGHTLY when empty.  That's actually pretty ideal for your
RV, but not so easy to dump off the side of a boat for
testing.

Used, old-technology, out-of-certification tanks are quite
cheap if you know some divers who are into keeping up with
the latest stuff.  I bought a mid-sized tank for less than
$20 from a local guy...

Used CO2 tanks (ie for soda machines) are likely to be more
common and cheaper.  Technically, CO2 only gets to about 800psi,
but the tanks tend to be standardized types anyway, and even
800psi is fine for 500feet.

BillW

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