Power/pressure washers: GPM & PSI - are they accurate, what is more important

[Ed Pawlowski]

So when the water hits the surface, there is no pressure against it? You can hold your hand against it and feel nothing? Velocity is the rate of change of position, pressure is what you feel.

[Pete C.]

There is force from the mass of the water impacting the surface at a high velocity, but this is not the same as the fluid pressure inside the hose.

[Ed Pawlowski]

True, but that force, or pressure is what counts, not the pressure inside the hose. As you move the nozzle closer and farther from the target, the force is going to change. Even though the figure is given in psi, the hole in the nozzle is very small too, not an inch. Just as light falls off as you move to increase the distance between the light source and target.

[sligoNoSPAMjoe]

...

I hope you are not planning to use the same tools for both.

Not very. They both likely will have inflated their numbers. This kind of misrepresentation is most common on consumer grade tools than professional or industrial.

It depends on what you want to use it on. I would go a little further and suggest that not only what you want to use it on but also what make and model tool, not just the GPM and PSI.

Sort of like asking what the Towing capacity and the fuel tank capacity is needed for for a car and not telling us what you want to do with that car. We might guess you want to tow a boat, but that could be a 40 foot power boat or a 10 foot row boat.

Would you tell you doctor you have a pain, and you want to know what to do about it and refuse to tell him where the pain is, or when you feel it?

>

[Some Guy]

Can you cite any authoritative source that has done any sort of analysis of several models of home, farm or light-commercial grade power washers and has come to that conclusion or made that observation?

It's highly likely that what you say is true - just like the HP numbers quoted for small gasoline engines have been in recent years. But I would like to see something in print stating their observations or measurements of these power washers.

Do you own or use any power washers?

Would you buy a washer rated at 500 psi and 1 gpm? If not, why not?

Even if I were to tell you, do you have the personal experience to know how many GPM/PSI is needed to do task 1, task 2, task 3 and task 4? Are you asking because if I tell you what task 1 is, you can tell me authoritatively, specifically, how many gpm and PSI I need?

Are you the doctor in this situation?

If I describe exactly what I want to clean, can YOU tell me the minimum PSI and GPM I need?

Or do you just like answering a question with another question?

[tnom]

Another way of looking at these two washers is to make a more common electrical comparison. This comparison difference will hold true in pressure washers also.

2gpm @2000 psi would be represented by 2amps @2000 volts 4gpm @4000 psi would be represented by 4 amps @4000 volts

Power = Voltage x Amperage So........ The 2gpm washer equals 4000 units of cleaning power The 4gpm washer equals 16000 units of cleaning power

• units of cleaning power undefined

• units of cleaning power are for reference/comparison only

[sligoNoSPAMjoe]

I have seen some test results, but nothing conclusive. I would expect that the numbers are real and under the specific text conditions, they are valid. The problem is each manufacturer, or even different models may be measured using different methods.

Yes

No. I would need to have more detailed information about the equipment on the market, which I have never seen, and there would be the difference in what I would consider minimum and what you would consider minimum.

If time is no issue, then why use a power washer at all. a standard hose will do the job. It may take weeks, but that 30 psi will do it in time.

I love answering questions with a question when the initial question needs clarification.

[Hustlin' Hank]

I just aquired a 1800psi 2 gpm with a B&S 4.5HP. It will peal paint. I was using a 1300 PSI electric that I thought was pretty good. For the typical non-professional consumer (like me), the 1800/2GPM will do most of what you want to do. If it is too powerful, hold the tip farther fromt he surface to be cleaned. Also, there are an array of tips that can be bought that will fit most jobs. Or, get an adjustable one.

Hank