Tank valves

[Frog]

Does anyone know if i get a "normal" tank valve on my tank (which i have yet to purchase) can the valve be removed and replaced with a Y valve? Here is the pic of the Y valve in question , just incase anyone needs to know? Thanks a lot.

http://www.h2oadventuregear.com/productinfo/rear.jpg

 

[Rick Murchison]

There are two "standard" threads in the neck of Scuba cylinders - so long as your "Y" valve's threads match your tank's threads, no problem.
Take it to your local shop for the work.
Even easier, take your "Y" valve to the shop and tell 'em you want a cylinder to match - then you won't have to buy a "K" valve you aren't going to use.
You do realize the "Y" valve pictured is a DIN valve, right?
Rick

 

[Frog]

Yes knew it was DIN, thanks very much for the info Rick
Cant you put inserts into DIN tank valves to convert them to A-Clamp, i could have sworn i saw that somewhere.

Thing is im having trouble understanding what tank to buy actually. HP, LP, 10% overfill (whats this all about?), DOT3AA blah blah lol. All i want is a Steel tank that is around 6-8 pounds negatively buoyant when empty. As for HP and LP well apparently some (?) LP tanks can be overfilled greatly , especially in "cave country" or so i have read. What does High Pressure and Low Pressure actually mean? But i havnt really got any idea as to which tank to buy because i dont understand the "standards" that i need to look for. + signs on the neck etc etc, i am very confuzzled.

 

[Rick Murchison]

Yes, you can get inserts for DIN valves - some of 'em. The orifice for a DIN valve needn't be big enough to accommodate the o-ring seat on a yoke first stage in order to work as a DIN valve, so you'll need to ask Beauchat if that "Y" valve has inserts that work.
As for tanks, it sounds like what you want is a PS 95. (it sounds like you want to use yoke first stage connection, so you should stick with LP tanks) As for overfilling, bear in mind that hydrostatic tests are done at 5/3 working pressure - and burst pressures for tanks in good condition are way higher than that - BUT - I do *not* endorse or recommend overfilling tanks (a 10% "overfill" is within the design limits of steel tanks with a "+" rating and is ok). Every time you do you stress the tank beyond its design working pressure and ultimately shorten the life of the tank. Those cavers who overfill routinely put in burst disks rated higher than the tank manufacturer recommends and whenever they move the overfilled tanks they are in violation of a bevy of DOT regs.
An occasional overfill (my original steel '72 that I bought in '72 gets filled to 3,000 psi from time to time because no matter how many times I tell a shoprat "this is steel - 2250 only" every now and then they don't pay attention - and it's still passing hydro fine) isn't going to make much difference, but doing it routinely is akin to overspeeding tires - they'll wear out sooner, and if you keep it up long enough you'll have a nasty surprise.
Rick
Rick

 

[Frog]

Thanks again Rick.

No i will be using DIN on the Y valve either converted from my existing A-clamp or i will be getting 2 new Apeks DS4 first stages.

Beuchat told me they only do a 3/4 thread Y valve ( I imagine that is in inch's?) Do british tanks have 3/4 inch necks ? i havnt got a clue. If not then ill have to start looking for another Y valve manufacurer. Cheers.

 

[Warhammer]

The only tanks that are going to meet your criteria are the Faber HP120 (-7.7lbs when empty), Faber HP100 (-7.5lbs when empty), and the Faber HP80 (-7.3lbs when empty). Some of the others like Pressed Steel have a little negative bouyancy when empty, but no where near 6 to 8 lbs. And no LP tank is going to have more than 1 or 2lbs of negative bouyancy when empty. Now, if you meant 6 to 8lbs of negative bouyancy when full then that's a different story. Have a look at the tank charts at http://www.diverlink.com/gear/tanks.htm and http://www.fifthd.com/gear/tankspecs.html.

These Faber tanks have in excess of 13lbs negative bouyancy when full. That's alot of non-ditchable weight to deal with and you wouldn't want to dive them with anything other than a drysuit. And doubleing them may also be out of the question, depending on your exact setup I suppose. I'd definately do a great deal of research before I dropped the $$ on these high priced anchors.

 

[Frog]

Well i said 6-8Lbs neg when empty because i want to get some weight off my weightbelt. I suppose i might have to settle for around 2-4 pounds instead going by your info. Is a 100 the same as a 15L? Out of my whole set-up how much in percentage would you say of weight shoud be ditchable?

Beuchat and Pressed Steel do not export to the UK so i need to find someone else who makes Y valves

 

[nobends]

Generally speaking, when you buy a tank, you choose the valve type. Don't buy it if it doesn't come with valve you want. Any yes, you can swap the tank valve at any time.

 

[Warhammer]

I assume your going to switch to a backplate/harness/wing setup, correct? You'll drop some weight by using the backplate. How much depends on the backplate and I'm not well versed on them so I'm not the one to ask about those. You'll also drop some more weight by going to a steel tank, how much again depends on the tank. But you can definately go too far with this and get to much non-ditchable weight.

It really depends on your complete system as to which tank is best for you. You'll just have to crunch the numbers to determine that. Don't forget to consider the tanks "real" weight as well as it bouyancy and actual weight. The real weight is the actual weight + bouyancy.

 

[Warhammer]

I didn't mean that you couldn't loose 6 or 8lbs from your belt by switching to a steel tank, you can. But you must also consider other factors. Is this weight being lost from the whole system or is it just being shifted from one location(the belt) to another(tank), or both? Let me give you an example, maybe that will better explain it. Let's say you currently dive a conventional BC, drysuit, 25lb weight belt and AL80. Let's say your drysuit, BC and all other gear weighs 20lbs. An AL80 weighs 32lbs empty and has a +4.1lb bouyancy empty, for a "real" weight of 36lbs. So that's 25lb(belt) + 20lbs(gear) + 32lbs(tank) = 77lbs total system weight.

If you switched to a Pressed Steel HP100. It weighs 31lbs and has a -1.4 bouyancy empty, for a "real" weight of 29.6lbs. You'd drop 5.5lbs from your weight belt because 4.1(AL80's bouyancy) - -1.4(PS HP100's bouyancy) = 5.5lbs. So you'd carry 19.5lbs on your belt. Your total system would weight 70.5lbs, 31lbs(tank) + 19.5lbs(belt) + 20lbs(gear) = 70.5.

If you switched to a Faber HP100. It weighs 38.8lbs and has a -7.5lb empty bouyancy for a "real" weight of 31.3lbs. You'd drop 11.6lbs from your belt (4.1 - -7.5 = 11.6) giving you a 13.4lb belt. But at the same time your total system weight would be 72.2lbs, more than the PS HP100 but less than the AL80. With this tank you just swift more weight to another aera, ie the tank. If you then added a 6lb backplate into the picture, as I think you're about too, your weight belt would now only be 7.4lbs. You'd probably be fine with this setup as long as you was in a drysuit. But if you dove without the drysuit then you'd probably not even need a belt and still be negative, prehaps too negative. Course if you're going DIR then wouldn't even consider diving it in a wetsuit, right? If you eventually doubled these tanks, then that too would put you not even needing a weight belt and right at neutral without a belt. See what I mean?