Back when I was an equipment supplier guy, we always used 3/8” stainless steel tubing for self-serve installations. The installers used simple hand-held tubing benders to custom install each facility. The tubing terminated near the pumping station and above each bay’s roof/ceiling penetration.
Inside the poly-iso insulated plumbing trough, the tubing was secured with CushNClamps (sp?) and UniStrut on about 6-foot spacing. The same materials were used to secure the tubing to the engine room walls.
Each tube was coupled and terminated with SS compression fittings…that’s the expensive part of the package! The ends were fitted with 3/8” compression x 3/8” MPT fittings. This allowed for the use of less expensive connections to the pump and boom hoses…and for installation of 3/8” check valves, tees, etc.
My 8-bay was equipped in this manner shortly after taking ownership in 1993. The stainless tubing was never an issue. The tubing inside the insulated trough, has withstood several -20F assaults.
At the time, the tubing/fittings/labor expense was approximately 10% higher than 100-R1 and crimped fittings. Additionally, my “hook-up” hoses…one length for trough to boom and one length for pump station to ss tubing…2 relatively short spares!
A well thought out and careful SS tubing installation will last the life of the wash…and it’s maintenance and worry free…well, except for the hook-up hoses. Plus, you’ll eliminate slow
soap-to-rinse changeover time due to saturated hoses.