Changing to Miflex hoses on a ScubaPro rig

[sirket]

I decided to swap out the hoses on my rig with some new Miflex hoses (existing ones were all the wrong lengths and were too stiff for me).

I had a few questions on the subject:

1. I replaced the HP hose on my SPG already. I inspected all the O-rings and tightened down the nuts to hand tight plus an eighth or so (no tighter than it came from the factory). Do I need to go back and change the O-rings as well (the SPG is only a year old). Is that likely too tight, too loose, or probably close enough?

2. I accidentally loosened the aluminum star nut on my S600 second stage (the one closest to the reg body) when removing the hose. I re-tightened it but I don't know if that nut has any effect on any of the internal seats or settings. Is anyone familiar with the S600 and can comment?

3. How often do you change out the O-rings on hoses and the like?

Thanks,
-Don

 

[DA Aquamaster]

The inlet fitting nut should be snug but not overly tight - too tight and it can crack the case.

Mostly it just helps the air barrel in the case, but it has to move a ways before it would leak.

The small 03 sized o-rings on the high pressure spindle will go several years without being replaced, but it's cheap insurance to replace them annually.

I replace all the static hose fitting o-rings annually. Thats arguably over kill, but again it's cheap insurance.

The most critical o-ring is the small 010 sized swivel o-ring that lives in the second stage end of the low pressure hose. It is a dynamic o-ring that can be exposed to sand, silt, etc and can wear fairly quickly so annaul replacement of it is a must. Also, if the hose is not secured snugly to the inlet fitting, it can unscrew and if it unscrews more than a couple turns the o-ring will no longer be supported and will extrude.

When tightening the hoses onto the first stage, you want to just snug it up the tiniest bit past hand tight, as excessive tightening will stretch the end fitting on the hose and can lead to failure.

 

[DreamSurfer]

I agree w/ DA... I moved from the beach area to the desert in LA county, CA for a year & found I was having to replace O-Rings every 6 months, instead of every year... Granted I was diving every week-end (teaching) AND the smog. heat & dry air seemed to make O rings (& ever diaphragms) go VERY quickly! O rings are VERY inexpensive "insurance". When I'd rebuild out there, I'd replace any "soft parts" & it became a habit, and a good one at that. I never had any O rings, or other soft parts fail & expect to keep it that way, yet when living in a smoggy area, parts can & do break down faster than if you live in a cleaner air, cooler area.

It never hurts (& is prudent) to replace all your soft parts, clean hard parts in an ultrasonic tank & calibrating them w/ a bench-test every time on an annual inspection/rebuild.

As for other O Rings, yes, they can last a VERY long time, and I have kept a new tank O ring connected through my 1st stage cover keeper line for roughly 20+ years (I'd have to look at my old dive logs to be sure of the date), and once in a while I'd test it just to see if it still sealed OK, it has sealed just fine, yet there is oxidation & I certainly wouldn't trust it on a dive now, as it has clearly hardened & started visibly oxidizing the 1st few years. I originally put it there to have easy access to a tank O ring if one failed, then over time kept one elsewhere, out of the water, sun, heat, etc. & left this one there.

It is now FAR harder & I doubt it would seal, so time to toss it. I could easily break it with my fingers. No telling if it would actually stay put & not fail under depth, just was an interesting experiment in how long these little things could last in the environment, and yes, you could feel & see the difference in the 1st couple of years & more so over time.

Even still, with the changes I saw in just the 1st couple of years, it was clear why it was a good idea to change these every year - ALL of them. No point in trying to stretch out the use of an O ring, only to have a possible failure - especially at depth. If you already have your regulator apart, best to change out everything, clean everything & calibrate everything every year.

 

[Doubler]

Unless they have vastly improved the Miflex HP hose, I'd have a spare HP hose in my save-a-dive kit. Cheap trip insurance.

 

[Jim Lapenta]

One of the reasons many service kits come with o-rings to replace the ones on the hoses as well. I also replace all of them when doing my annuals. I may also swap them if I change hose configurations as I was having to do before I got enough regs to make doing that unnecessary. Now with nearly a dozen in various configurations it's pretty rare that I have to do that. From stages to rigs for singles and doubles, Din or yoke I'm covered.

 

[sirket]

I have a spare HP hose in my bag so no worries there

 

[sirket]

I just got back from a week of diving with the new Miflex hoses and I have to say that so far I am very happy with them. Reduced weight, more flexible (meaning more comfortable and easier to pack), nice quality.

The reg hoses didn't push or pull my regulator for a change. The hoses just sort of disappeared which is what I was hoping would happen.

The small HP hose was very nice- I don't have a full console, just an SPG, so the small hose is nice. Keeps it out of the way and is very flexible.

The inflator hose made no difference, it doesn't get in the way normally so having a Miflex hose there was not important.