Bob, I have a question for you since you are the Sapphire guy. This thing has been eating at me so I need to ask. I have a friend whom just purchased a new 570. I went to visit him on a job yesterday and noticed that the pressure relief valve seemed to be hissing like mad. He was only pulling 5 to 7 hgs. I pointed it out to my friend and he said it was supposed to do that. Really? It is supposed to open at 5hgs?????? I always thought they opened at 13 to 15 hgs and then when they did, it was a bit of a chirp, rather than a constant hiss. I would think he is losing CFM due to the relief valve opening at such low hgs. My firend is convinced it's working properly, but I'm not so sure. Every TM relief valve I have ever seen never opened at low hgs to enable parasitic cfm loss. Bob, does you SS hiss through the hgs range?I have 2 units can probably shed some light in what is happening. You are correct the 570 is not designed to bypass.
The problem you are having is cavitation in the water box. Basically the fresh water box under the blower is not filling up all the way. This is because there is no where the air inside has no place to escape to.
The box should have a brass pressure relief piece on it, right behind the driver seat. If it isn't there call sapphire and talk to Scott and get one.
If you are also not having enough vacuum make sure your filters in the tank are clean. Also make sure you not losing vacuum because some hose clamps are not done properly.
Like I said I have 2 and my first machine had the same issue you described. This is the fix and the problem went away. The second machine came with it from the beginning with no issues. We dual wand all the time with it and have more than enough vacuum. This tells me you have a leak in the vacuum circuit.
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