I built a 2 step gun based on the other thread floating around, but Im having some problems with it pulling soap. Itll pull through both lines with a soap nozzle but not with my high pressure nozzle. When I pull soap with a true soap nozzle, itll surge back and forth between a fan pattern and somewhat high pressure 0° soap.
@TaderzNgravy, have you done your maths on injector size vs. nozzle size? You need something like a 30% pressure differential to draw soap. Due to that issue, I think the high pressure 2-step guns max out at 1800 psi or so, that would be a size 8.5 nozzle on your machine.
Btw, nice job on building the gun. Do you have a link for that 3-way valve? And did you happen to piece the check valve and injector together with an adapter you found, or just bought it prebuilt?
First thing you’ll want to do is find your maximum pressure injector. That is, the smallest size injector that will still allow 5.5 gpm of flow. That will likely be an injector with a size 7 orifice, .067” or 1.70mm. You might have to go one size smaller and drill it out with a 1.7mm bit.
5.5 gpm with a size 7 orifice generates 2500 psi. Multiply by .7 (subtracting 30%; taking a quick math shortcut here) = 1750 psi.
Use the chart to find the proper high pressure tip: 8.5.
That should theoretically pull soap at maximum pressure. You could even experiment and see if it will still pull with an 8.0 tip.
Ain’t that the truth. These calculators are based off of perfect world scenarios, not accounting hose length, diameter, plumbing restrictions, wear and tear etc, in other words everything matters to get a result.