Not to hijack your thread, but I'd like to put my pressure washer in a nook, and plumb it to a few spots around the place. Has anyone ever done hard plumbing for high pressure water, and with what pipe?
1/2" schedule 80 pipe has a working pressure rating of 3000 psi after derating for the threads at fittings. The important thing is to use only forged steel fittings for all the ells, tees, and couplings. Forged fittings also have a rating of 3000 psi working pressure. Burst pressure on both pipe and fittings is several times working pressure rating, so even though the system may be operating at max working pressure it is nowhere near its burst pressure.
If I was piping anything for high pressure, I'd check with local pipe, valve, and fitting suppliers and find out which of them carries US made pipe and fittings. Wheatland Tube, for example is a top quality US manufacturer. For high pressure use I wouldn't trust any imported pipe or fittings. I've run thousands of feet of imported pipe on welded installations working at 200 psi or less with no problems, but on any screwed pipe I have always used domestic pipe because I've never seen a piece of Chinese or Indian pipe that would thread worth a damn.
An alternate would be hydraulic tubing, but the cost of fittings would be a killer and the tubing itself would likely cost as much as, if not more than, the 1/2" sch 80 pipe.