I'd say that valve will not support the flow needed for your power washer. You would need to shut off the water to that line (probably the house) and cut off that valve and sweat another one (ball valve) in its place. You will need to know the supply size, I'm saying 1/2" and go from there. Supply houses will have all the parts you need, just ask someone there. If the water supply won't shut off completely, us the bread trick (white bread kneeded into a ball and shoved into the copper to stop water flow- after sweating the new valve, turn on water and open valve). If you don't know how to use a torch, you might be able to use compression fittings for the new valve. Or...borrow a pro press gun and crimp the fittings on. (Probably will not find one unless you talk with a plumber)
Can't tell from the pic if that valve is threaded on, but it looks like it is soldered. Threaded would be much easier..just replace valve.
Last edited by dirty vert; 01-12-2013 at 10:49 PM.