Many consumer grade pressure washers specify a minimum pressure for the supplied water, which is sometimes well above the low end of household water pressure. Our water pressure is often low and I'm looking for a way to verify without a pressure meter that it is adequate for this purpose.
Data from the utility company isn't useful. The pressure is very affected by the usage of other houses in the area, plus there are endless effects on the pressure between the water meter and the hose bib. However, I can use the water at off-peak times and test it at the hose at the time I want to use it.
The formulas I've found online tend to deal with what happens inside the pipe or between one point and another. They require all kinds of parameters that aren't really relevant to this problem. I'm only interested in what comes out the end of the hose.
I know that for pressure washer nozzles, the area of the hole relates the flow rate to the pressure, and one factor can be calculated from the other two. A garden hose is at a very different scale; characteristics that influence flow at high pressure on a tiny scale aren't likely to extrapolate well. Nevertheless, the same physical laws should apply.
The end of the hose is a 3/4" hole and I can measure the GPM coming out. Can the PSI of the system driving the water out of the hose be calculated from just those two factors?
I've looked at the standard model of a water tank with a hole in it, which would seem to represent this. However, the results were nowhere near the same ballpark as household water pressure.