I just finished a system like you described. The hose I used is SAE
30R7 fuel line hose which is rated to 50 PSI.
I used Western Enterprises fittings from Arc-Zone to couple to the
torch. AW-431 LH female to female, and AW-17 1/4" barbed "B" style to
the SAE 30R7.
I control the pressure going into the system with a pressure regulator
sold by Doitbest hardware stores that is for protecting motor home
systems and keeps the pressure under 50 PSI. Pressure ratings for TIG
torches I've been able to find is 50 PSI max.
I also use a 10 micron water filter made by Culligan to keep the water
entering the torch clean.
Any welding supplier can get you a 5/8" left hand hose barb fitting for
the water fittings and a few connectors.
The most important part is a water filter.
I use a standard under-sink type inline drinking water filter.
It keeps sediment from clogging your torch head over time.
I have a ball valve mounted on the filter to turn the water on and off,
although a solenoid valve would also work.
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