Thanks to each of you for your advice. I knew it was a stupid idea but just needed someone to hit me upside the head to drive it in. I will indeed install them at floor level. Thanks for spending your time to help a newbie avoid a serious mistake.
Welcome. Since it is your own home, you may want to install a drain at the bottom of the space your source manifold is in. Here's what I did to get the size of the drain needed for the worst case of a pex tubing popping off a fitting:
- Got an empty 3 qt. grape juice plastic container.
- Cut a small hole in the bottom of the container.
- Put a garden hose in the top of the container & turned the water on full force.
- Observed the drainage from the hole.
- Enlarged the hole until the drainage was able to keep up with the maximum flow from the garden hose.
- Then doubled the size for my drain.
In my case the box housing my manifold is outside of our house (it never freezes here). So I just cut a rectangular hole at the bottom of the box, (which is a few inches above our carport floor level), and stapled a screen to cover the hole to keep insects out. My drain hole actually ended being about 3 times the size obtained from the test procedure above.
But frankly, after seeing how well the Wirsbo/Uponor expansion method shrinks the tubing and expansion ring around the fittings, I'm 100% confident that the tubing will never pop off the fittings. I also supported every tubing near all fittings so there's no sidewards tension on any fitting to prevent the fittings from breaking.
Be sure to allow for a LOT of expansion and contraction in your hot water lines. One inch per 100 feet for every 10 degrees Fahrenheit of temperature change. Assuming your lowest ambient temperature that your hot water lines will be exposed to is 50 degrees and your hot water temperature is set to 120 degrees, that's a 70 degree temp change. That's 7" of tubing length change for a 100' run, or 3.5" length change for a 50 foot run.
Best of luck on your diy pex plumbing project,