I was servicing my regulators yesterday and noticed something that I'm not sure about. I had them under pressure in a tank of water and was checking seals, pop off pressures, inhalation pressures, etc and noticed very tiny little bubbles on my high pressure hose...the one going to my gauges. There were only a few and they were not bubbling or leaking. They looked like sweat. I wiped them off while it was all still underwater. They came back right away. They never did get big enough to bubble off but did come right back when I wiped them off. Anybody ever see anything like that before? Is the hose actually starting to seep and go bad? Thanks for any info.
This is normal and will happen even with new hoses. The bubbles are most noticeable on a hose that is new or that has not been used in some time.
Here's why. Rubber hoses are built in multiple layers. At a minimum, there's an inner rubber tube, a braid over that, and an outer jacket to protect the braid. Sometimes there's more than one layer of braid. Sometimes there's more than one layer of tubing, either between braids or over the inside tube depending on the design of the hose.
The braid has gaps in it and these form trapped spaces because of the outside tube and the inside tube. To allow these spaces to equalize, most SCUBA hoses have a perforated outer jacket with pin-prick sized holes roughly every inch in a line along the length. When you pressurize an HP hose, the inside tubing stretches partially into the gaps in the braid. Whatever is in the gaps in the braid will be partially forced out of the jacket through these pin holes -- either air (bubbles) or water (weeping), or a combination where they kind of spit. Look at the source of the weeping or the bubbles, and if it's every inch in a line, you can be sure that it's from the perforations. The weeping or bubbling will eventually subside even if the air is left on.
If you want to be sure it's not a leak, leave the air on with the hose submerged. If there are still bubbles coming out after a reasonable period of time -- I don't know, 10, 15 minutes, an hour -- you have a leak.
How else can you tell if a rubber hose is shot? Absent a leak, if the integrity of the outer jacket is compromised (tears, holes), the hose should be replaced because the jacket can no longer protect the braid. Loss of flexibility is a warning sign. Corrosion of the fittings is a warning sign. You can look at the date code stamped in the crimp and see how old it is, since the rubber will degrade chemically whether it's in use or not. The maximum age is debatable but it is one piece of the puzzle.
All this is true of HP and LP hoses alike but the bubbling/weeping effect is more pronounced and more noticeable with HP hoses.
