Saturday, 17 March 2012


I took a couple of diver's scuba tanks - which  I use for filling my precharged pneumatic air rifles - into the dive centre this morning... and found out something that I never knew. 

One needed to be sent away for a full hydrostatic test; the other was still 'in date' and could be filled there and then. As many PCP owners will know, if you fill up from an air bottle, for that scuba tank to be itself filled with breathing air by a diving centre, it must be 'in test'. 

But this is where things get complicated. Surface-use-only valves only need to be tested every five years (a full, hydrostatic test). Those bottle with valves which could be used underwater for diving - regardless of whether they are or not - need to be tested every two-and-a-half years. The tests alternate between a visual and a hydrostatic test.

How to tell which type of valve you have? Well, if your tank has a gauge pre-fitted to the valve - like this slow-flow 'Jubilee' valve from MDE (below) - it's 'surface-use-only and requires a full hydrostatic test every five years. 
Surface-use-only valve (it's got an integral gauge)

However, if it has not got an integral gauge fitted, like the one below, then even if you tell the diving centre that you've never taken it underwater, they will still treat it as a below-surface valve and, as such, the bottle to which it's attached will need to be tested every two-and-a-half years - visual, hydro, visual, hydro... and so on.
Below-surface valve (no integral gauge)
But here's the thing I learned from my dive centre this morning. If you have a bottle with a below-surface valve, make sure you get it into the dive centre pretty close to its test date when it's due for the visual test - because if you leave it too long after, the dive centre will probably want to give it a full hydrostatic test. This, of course, costs around twice as much!

I learned the hard way. Although my bottle was technically due a two-and-a-half year visual, because I'd left it almost a year - as it was full at 'clockover' date, and because it's only my 3-litre 'emergency' bottle which I rarely use, I'd had no cause to take it in to the dive centre - I got thumped with a £42 bill instead of a £25 bill!

So... I just thought I'd pass this info on. Check your scuba bottle's test expiry date - either etched in the bottle, or on  a sticker - and don't leave it too long afterwards before you decide to take it to your dive centre for its scheduled test! 


  1. So, just to confuse matters further Nigel, where would someone stand if they had a cylinder that has been used below water in the past BUT, they had retro fitted a 'surface only' valve?

  2. That's a good one! I suspect that it will be down to the individual diving centre. What I think would happen is that they'd look for the date at which the surface valve was fitted; if there was evidence of the date, then they would go follow a 'surface only' format. If there was no evidence of the date, for a belt-and-braces approach, they'd apply a 'below surface' policy.

  3. Hi all, I have very recently started shooting again after 40 years. I went to my local gun shop this week to buy a cylinder, I asked if it would have the full 5 year test,he informed me that it is now 10 years, he said that he had been informed only this week by the powers that be that this was the new rules. I haven't been able to confirm it yet. Rab

  4. Rab - not heard this, but would be most interested to find out more. Could you give me the details of your filling centre, I'd like to contact them to enquire more? Thx, Nige

  5. Hi nigel, it was neath gunshop 01639 632768 .Rab

  6. It's a bit of a can of worms, Rab - and I've clarified the situation with Neath Gun Shop. And, also, nearby Keen's Shooting Super Store... it's as a result of them refusing to fill someone's bottle that Trading Standards got involved. Unfortunately, TS's reply has rather confused the issue. Basically, it's 2.5 and/or 5 years for bottles that are rated for diving use, where the period is dependent on the valve type as discussed above. BUT... if the bottle is rated for industrial use (i.e. it's marked up with the BS/EN figure accordingly), then it's every 10 years (unless it had been inadvertently fitted with a diver's valve!). In the majority of cases, airgunners' bottles are of the diving tank (aqualung) variety so - according to their valve type - the must be tested much more frequently than 10 years. HTH. Nige

  7. Hi Nige, thanks for that.The cylinder I bought was a 3 ltr one with the valve and guage attached as in most of the ones Ive seen for sale,this is the one I was told it was a 10 year test on so if this is the case I guess more shooters will be buying this type in future.. atb... Rab

    1. Rab you have the 5yr test , as explained . the industrial tanks wont be used by airgun fillers or divers unless fitted with a dive or airgun valve then its back to use and tests of a 5yr test .

  8. Thanks for posting this. I truly had no idea about this stuff. I don't shoot regularly (occasionally with a friend), but am super interested in it all. Again, thanks for posting.

  9. Hi Nigel,
    Does the same apply to carbon bottles? I have just purchased a carbon bottle with an expiry date of 2032. It states next test is due in Jan 2017 and all this information is clearly marked on the bottle. However, my bottle is fitted with the "below surface valve" so where does this leave me?

  10. hi, i live in sheerness kent does any one know were i can get my 15ltr bottle , tested and , thanks ray