I decided to do some testing yesterday with my relatively new foam cannon and my gas powered pressure washer. Here's a little background before the testing I did. When I first received my foam cannon from AutoGeek I was initially very excited as I was expecting the thick snow like foam just like the YouTube videos showcased. I was let down shortly after my first use of the cannon. I used 2-3oz. of shampoo and filled the rest of the 32oz. with warm tap water. As I read on the forums I was thinking this would be enough.. What I experienced was nothing like the videos on YouTube, the soap was barely enough as you could imagine and no where near the 'snow' one would expect from a foam cannon. So I did a little bit of research and it turns out the water in my area is quite hard. According to the boards I must now use anywhere from 6-8oz of shampoo for the 32oz bottle. This is where I decided to test. So I used 1oz of shampoo for every 4oz of water. I tested with about half the bottle filled with water (about 16oz.) and put 4oz worth of shampoo. Then I set my pressure washer at 2000psi and had the knob on the foam cannon set maxed out to the "+" side (counter-clockwise). I experienced soapy water until about 4 turns in (clock-wise). That's when the foam was beginning to come out. Then I decided to turn up the pressure to about 2500psi. I experienced no change from the amount of turns from soapy water to foam (about 4 turns clock-wise). Then I decided to turn down the pressure to 1000psi and also experienced no change from soapy water to foam (with the same amount of turns). Each test was done with the widest fan setting. So as it turns out you do not need massive psi or massive gpm to have snow foam even with hard water.