You're actually correct. The gauge is ranged to like 60 psi but really should only range to 30 psi for better accuracy.

At low range it's running under 10 psi, I believe about 6 psi. When the filter is plugged and the pump is reading about 26-28 psi on high speed it doesn't really change low speed pressure as much. Low speed is still under 10 psi, I believe about 6-8 psi but I haven't looked at it real close. Now that I think about it 6 psi is probably about right.

I was just rounding to 10 psi but it is definitely under that.

Thanks for all your help.