The SCUBA unit


  • First, take the cylinder and stand it upright.
  • Fit the cam-band on the Bouyancy Compensator (BC) over the cylinder, and slide it about halfway down. The top of the backplate should be about level with the bottom of the shoulder of the cylinder. The outlet from the cylinder should point towards the back of the BC.
  • Ensure that the cam-band is threaded properly, and tighten the cam-band - if you can't tighten it enough get someone to check it, or give you a hand.
  • Check that there is an O-ring and that it isn't damaged or perished.
  • Turn the cylinder on and off quickly to generate a short blast which will remove any debris from the orifice. Check that you haven't blown out the O-ring.
  • Take hold of the DV and hold it in front of you, with the 3 or 4 low pressure hoses at the top of the DV and the A-clamp towards you.
  • Check that the sintered metal filter in the DV is clean. If not, your DV probably is overdue for a service.
  • Check the pressure gauge is on the left, as is the longer of the two DV hoses (the octopus regulator). The other DV hose (the main regulator) should be on the right. All other hoses can go either side.
  • Unscrew the clamp and remove the dust cap.
  • Place the DV on the tank so that the round filter fits onto the O-ring. Tighten the clamp so that the DV is not going to move but DO NOT OVER-TIGHTEN. It only needs to be finger tight - the air pressure will seal the A-clamp onto the O-ring.
  • Connect the direct-feed hose by pulling the connector at the end of the hose back, and placing it onto the nipple, then releasing the connector.
  • Place the front of the pressure gauge against the side of the cylinder and turn the air on. Remember that you should not need to force the cylinder open.
  • Check and note the cylinder pressure, then turn the air off. Wait a minute or so and check the cylinder pressure again. Because the hoses will expand slightly, the pressure will have reduced, but probably by no more than 5 to 10 bar.
  • Place the front of the pressure gauge against the side of the cylinder and turn the pressure on again, and check the cylinder contents again.
  • Take two deep breaths off the main DV, watching the cylinder contents gauge, and checking that the airflow does not fluctuate and that the air does not taste of anything. Keep breathing from the main DV until the contents gauge reads zero. Gently try and breath further - you shouldn't be able to, and if you can, then you have a leaking DV exhaust valve, or a hole in the mouthpiece.
  • Repeat the exercise with your octopus DV.
  • Place the front of the pressure gauge against the side of the cylinder and turn the air back on.


  • Turn the cylinder off, but DO NOT OVER-TIGHTEN.
  • Purge or breathe all the air out of one of the DVs.
  • Disconnect the direct feed hose, by sliding the connection backward at the inlet to the BC.
  • Remove the first stage from the cylinder, and blow the dust cap dry. Dry the dust-cap with your own breath - don't use the cylinder's air to do it. Fit the dust cap in place and tighten the screw on the A-clamp until it is firm.
  • Loosen, but do not undo, the cam-band on the BC. If you undo it you may have problems fitting it next time you come to dive.
  • Remove the BC from the cylinder.
  • Lie the cylinder down.
  • Drain the STAB of water, by holding it upside down and pressing the dump button on the direct feed.
  • Wash the DV and BC in fresh, clean water.

This page was last updated on : 09 Sep 2018