I prefer 4 nozzle bar, gives a more even clean in 1 pass. I use 25025s on concrete and 2504s on pavers or cooldeck
2502.5 s what I run with 4 nozzle in mine
We ALWAYS REFER to the charts provided by the ENGINEERS at General Pump, Cat Pump, Udor, Comet, Alkota, AaLadin, Pressure-Pro, Delco and countless others. Whisper Wash even uses the same exact charts. Barens provides a very useful nozzle calculator. I’ll provide the link below. You can plug in the 8 gpm at 3500 and see that the 2.5 nozzle is required on a 4 nozzle spray bar!
It’s quite simple. Use nozzles that are too small for your pump and you will force back pressure on your unloader forcing it into bypass over and over.
Why restrict the flow? Talk to an engineeer regarding the required nozzle orifice on a 8 gpm at 3500 pump using 24 gas hp. He or she will explain that the nozzle orifice is somewhere between 8.5 and 9.0 in order to reach the 8 gallons per minute at 3500 pounds per square inch.
Divide that number by the holes in your spray bar.
8.5/2 is 4.25
8.5/4 is 2.125
General Pump and Spraying Systems do not manufacture a nozzle orifice of or 4.25 or 2.125. Pump manufacturer’s recommend that you go up to the next orifice ALWAYS rather than restrict. The next orifice is a 4.5 and 2.5. In this case use two 2504.5 nozzles and four 2502.5 nozzles when using a four nozzle spray bar. You are letting more water flow by using a bigger orifice.
I hope this helps to clarify. Call any of the pump manufacturers and speak with the engineering department. They will fill you in.
It is my understanding that the GX690 is NOT 24HP.
According to HONDA…the GX690 is 22.1hp.
So, it will not generate 3500psi using widely accepted formulas for calculating psi…IF the correct horsepower is entered…the correct psi will be calculated and the correct nozzle size can be arrived at.
Hence, IBS’s statement about it being a lie or ignorance.
Correct Jim, vendors lie about specs to make sales then come on forums to get free advertising. The legitimacy of a vendor goes down by the amount of their posts. Plus, using false specs throws off the nozzle calculations and related issues.
Anyone using General Pump’s nozzle chart is using an incorrect chart, anyway.
See here: http://www.generalpump.com/PDFs/RESOURCE%20INFORMATION/NozzleChart-Equations.pdf
Check the 3.5 and 4 orifice @ 3500 psi and higher.
It’s wrong anyway.
I use a different chart now.
Thanks ALL for participating in this thread. Since there is conflicting info, the more responses, the better!
I think you guys are making this a bigger deal then it really is.
Second thing is why is everyone trying to run their surface cleaners at max pressure anyway? Concrete does not require 3k + psi to clean anyway so why not go up a nozzle size and save your pump, unloader and the concrete.
You won’t have 3k at the surfacer. You might save some concrete but you aren’t saving the pump or unloader. Either way, do what works for you and your situation. I just get annoyed at vendors making uneducated statements and/or lying.
Actually, I’m trying to get the most gallons per minute, not maximum pressure. That’s why I want to use larger hose, quick connects, nozzles, etc but not so large as to reduce the amount of psi my washer can produce at normal operating conditions.
Well I ran four 25025 nozzles on my Wisperwash 19" and stripped the “cream” off the top I guess it’s called. Exposed some aggregate. Cleaned a little too well I suppose. Not only did it take off the dirt, took some concrete off as well. Was hoverring a little. I will need to lower the pressure before doing any more residential concrete. Maybe four 2504 tips? Residential driveway about four years old. Too soft, I guess. Is concrete that is “floated” and broomed softer than concrete that is leveled using those rotating spinners?
I can’t seem to wrap my old brain around these charts for some reason. I keep waiting for that ah ha moment. Let’s say machine is 7.8@3000 going with 4 nozzles but want my pressure reduced to let’s say 2300 psi to protect concrete what size nozzle would that be?
From my understanding you would want 25025 nozzles. Just divide your flow by the amount of nozzles then look for the orfice size that would give you ~2300 psi. If you really want to play it safe get 2503 nozzles but that should put you around 1800 psi which doesn’t seem like enough to me.
So if you are at 7.8 gpm, 4 25025s should put you about at that number, after 200 feet of hose you will be in that ball park.
you want 2502"s. All the talk about lowering pressure or adjusting for concrete is hooey. If the concrete is new. don’t wash it. If it has bad cream, don’t wash it. Lowering pressure by changing nozzles is just going to wear out the bar threads or waste time.
I’m having trouble understanding how to come up with those numbers using the chart above. My 8 th grade education leaves me lacking in some areas.
I have a 8 GPM @ 3500PSI 22 Horsepower machine (so the dealer claims) with a 19" wisper wash classic with four tip bar with 25025 nozzles and it washed the surface off this concrete and I had a milky residue runoff. So, I assume pressure was to high. Is there a way to determine, prior to washing, not to wash it as you state?
I have 225 feet of hose and it still washed off the top layer of concrete.
I wasn’t aware until afterwords, as it seemed to be cleaning well