I just received my first surface cleaner, 21”. I’m having a hard time understanding nozzle sizes. I would like to start offering driveway/sidewalk cleaning this weekend but i’m worried about using too much pressure and washing off the ‘cream’. I have a 4.5gpm 4500psi machine. The nozzles that came with the SC is two 25020 (25 degree and 2.0 orfice) will this be safe for cleaning newer driveways? And any help understanding the nozzle charts would be appreciated. Thanks
I think I am starting to understand this stuff. If you have 2 nozzles, half of your water is going to each. So that is 2.25 GPM. A #2 nozzle will flow 2 GPM at 4000 PSI by definition. Your 2.25 is more than 2, so the pressure is going to be more than 4000 PSI. If you put it in the formula, you actually get 5000 PSI. But your pump isn’t that strong, so you’ll get 4500 PSI and the unloader will recycle the rest of the water.
If you have 4 nozzles, each one is getting 1.125 GPM. That works out to 1265 PSI. Your machine is totally capable of that, so the unloader doesn’t have to do anything until you let go of the trigger.
Thanks, I understand a little better now. My surface cleaner has two nozzles so it sounds like 4500psi is way overkill. I read that 2000 to 2500 is ideal. Any more could ruin the creme on a driveway.
This is 2018, people. I am amazed nobody has made a website that calculates this stuff.
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You probably want 2503 nozzles or 2502.5
I’m understanding this a lot better now. ( I think) this time I did real math, but I messed up when I told you my machine was 4.5gpm. It is actually 4gpm, sorry about that. Instock, that cat pumps video helped a lot, thanks for posting that.
P2 = P1 ( F2/F1)^2
A #4 nozzle means 4gpm at 4000psi
So to find nozzle size required for my machine 4500 = 4000 (4/F1)^2 = 3.77
The manual for my surface cleaner says the minimum orfice size is half that which is being used in your pressure washer, so the minimum ordice size equals to be 1.888. They sent me a set of nozzles that are 2.0 orfice (4.0 orfice together)
Using these nozzles I should get 4000 psi
P2 = 4000 (4/4)^2 = 4000
Now this might be good but I’ve heard this is too much to use on newer driveways with cream still intact. Racer, I did end up getting 2502.5, thanks for your suggestion.
2.5 orfice would actually be 5 orfice together.
4000 (4/5)^2. = 2560 psi. This should be a lot safer, I believe. Using Size 3 orfice nozzles, pressure would be around 1777psi, I might get a set of those too.
So I appreciate all the help, now can you check my math and make sure I havnt done it wrong or left something important out? THANK YOU
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