The impact of tubing sizes

[gabe]

3/8" ID | 1/2" OD into 1/2" ID push-fittings is ideal

Stew:

I don't have too much time to post right now, so I'll go quick: please investigate minimum pressure specs for push-in fittings. As you know, I have tremendous experience with these, and I didn't give them up commercially without solid reasons..

Negatives in a nutshell:
Safety
- push-in fittings were designed for applications where pressure is <2-7> bars. They were never intended for low pressure environments.
- If you are going to use vinyl tubing and push-ins be aware that over time the tube seriously indents at the o-ring level, resulting in reduced o-ring compression and poor seal -think of the effect of a bend in the tubing at proximity of the fitting opening with an under specs seal! Furthemore tolerances in vinyl tubing OD often exceed those of most push-in fitting brands.
Other considerations:
- great to install, horrible to remove for the inexperienced
- expensive


Final consideration: In an extended use scenario, vinyl tubing is counter-indicated due to its high porosity. Alternative low porosity tubing does not work well with push-ins (in our application) for multiple reasons e.g.: hard tubing like polyethylene has low bend radius, and soft tubing like norprene is too soft for adequate seal.

Final final: the reduced pressure drop benefit offered by push-in fittings is incremental at best. Convenience of utilization for trained users prone to install/uninstall frequently is priceless. But they have lost MY vote of confidence for long term/no maintenance systems at this point.


Other than that, thanks for the thorough survey!