Newbie, installing "custom" system

[Mogman]

No chance of any sub-standard, out-of-spec fittings to which Tim alluded earlier? Not trying to give you a hard time, just attempting to get to the bottom of this.

To review: For a standard 5/16" (7.9375 mm) ID barrier hose, the fittings should measure—according to my Mitutoyo digital caliper—3/8" (9.525 mm) OD—that is, 1/16" (0.0625 mm) larger than the ID of the hose to ensure a tight fit before crimping.

That is what I am trying to figure out, it does look like the fittings, some of them measure as small as 7.6mm, I did purchase a couple ATCO fittings and they came in yesterday, they measure 7.95mm which seems much better, I have a couple more coming in from ACKITS tomorrow but I feel pretty confident the issue is the fittings.

[JohnHere]

The ATCO fittings at 7.95 mm OD seem about right. The ones that measure as small as 7.6 mm appear to be out of spec to me.

[Mogman]

The ATCO fittings at 7.95 mm OD seem about right. The ones that measure as small as 7.6 mm appear to be out of spec to me.

The order came in from ACKITS, their fittings measure 7.95mm (correction my calipers were not zeroed), they evidently did not read the notes as I asked for a sample of their #6 hose.
Considering they have a 15 foot min. it did not seem like an unreasonable request

[Tim]

The ATCO fittings at 7.95 mm OD seem about right. The ones that measure as small as 7.6 mm appear to be out of spec to me.

The order came in from ACKITS, their fittings measure 7.85mm, they evidently did not read the notes as I asked for a sample of their #6 hose.
Considering they have a 15 foot min. it did not seem like an unreasonable request

I did read the notes for a free sample of the hose. We ship from major suppliers and they don't cut foot sections off a 500ft reel. That's why there is a min, plus overhead of an employee packing up and processing the order. Not my call, just as I have a 15ft min! I have to play by the supplier's rules as well.