MEP001
Well-known member
The things you have circled are unrelated. The booster pump runs presoak at low pressure to the gantry. It goes out on a single hose to the mess of T's and check valves on the wall.
The f**k that does is control the air to foam the presoak.
None of those will cause your pump to lose pressure from lack of flow. The high pressure pump sounds like it's not getting water. This unit uses an air-operated valve on the pump input to control the source of water. That's the valve on the plumbing with the two yellow tubes going t it. Either it's bad (I am not familiar with this one so I don't know if it can even go bad and stop all water flow) or the giant PVC check valve above it is stuck closed (Highly unlikely but I have seen it happen).
They definitely can go bad. They are check valves. You will know pretty quickly if any of them go bad because the air from the presoak will probably push its way back through and bubble up inside the presoak tank. If you suspect one is bad but you aren't seeing air in the tank, get a long pair of needle nose pliers and with the machine running high pressure (not undercarriage) gently pinch the hose closed. You will see and feel the pressure coming back through.
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