Nozzle orifces

Waterboy

Waterboy

New member
Need help from someone that can explain in baby talk how the the various nozzle sizes (orifices) relate to the output of the psi and the gpm of a Pressure Washer.

I am looking at a 4gpm w/ 4000psi output.

I have looked at the chart at Delco's and I am close to clueless on how to read it.

The only thing I can figure out is that to stay at 4000psi I would need a size 4 nozzle.

I have done a search on this site to locate a better explaination but am coming up empty(could be user error)

What I am ultimatly looking for would be what size to use to obtain 1000 / 2000 / 3000 psi. No I take it back, that would be the basics. I would really like to either understand Delco's chart or get someone to help me understand it.

If you think your up to the task then please help as I am a new in this line of work and am eager to learn what you already know.

Thanks in advance for any and all replys

Robert
Precision Power Cleaning
 
You are correct that a 4gpm/4000 psi machine needs a size 4 orifice to sustain that output. I always adjust pressure with orifice size and not unloader. This will keep gpms up. As the orifice size number gets larger, the opening is larger. I don't have the chart in front of me, but if you use that 4gpm machine with a size 7 orifice, you will get about 1500 psi. As you increase the orifice size, your pressure will continue to drop. Just think about using your garden hose without a nozzle on it. Same amount of gpms, but pretty much no pressure. Now close off part of the hose with your thumb. Your orifice size is reduced greatly, and your pressure increases. You just have to play with them to get what you need. If you went to the far end of the chart with a size 30 orifice, you would prob have less than 500 psi.

Just remember...the larger the orifice number=larger orifice=lower pressure...

Clear as mud?
 
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Chris - Thanks for answer !

What seems like a confusing (muddy) fog is all clear now.

Going to Delco's Chart I can see that what I need to do is locate in middle of the chart the GPM of the machine I am using and goto top and for the PSI i want and follow it over to left for the correct nozzle orfice.

Light shines on Marble head :eek:

Brings up another question...Is the unloader nessesary?

Are there times when I would want to back down the GPM? If there are then what would those be for?

Thanks for the knowledge

Robert
Precision Power Cleaning
 
Hi Robert,

You shouldn't really have an application where you would want to reduce your flow. The flow is in reality your cleaning power. You basically understand the chart correctly.

Following the chart below you pic the pressure you want and follow it down to your GPM in the far left column. Where the 2 intersect is the number which represents the orifice to create that psi at that gpm. Pretty simple once you understand it.

Greg Rentschler
www.deckguide.com
 

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Greg - Thanks for including the chart.

I should have included the link at least.

I am guessing then that the unloader is something not be messed with then.

Friend of mine that has a PW business backed his down when he was new and never been able to get it to the right setting again.

He is probably using a 4GPM output machine at around 3GPM. O well.

Only other reason I can think for not using it is the fact of having to get down from roof to change it has oppose to just changing at the tip.

Well thanks for the Clarity

Robert
Pecision Power Cleaning
 
Here are the Formulas for Nozzles
 

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There have been a few times that i had to change to a smaller tip so that i did not run out of water on a job. but i am using a lager machine than you
 
Chris Francis said:
Question about nozzle sizes also will larger one harm the engine I was told that if you run the your engine with larger size tips puts more back flow more weare on the engine.
Click to expand...
No, if your water is backflowing something has broken, pw pumps are positive displacement pumps. Just listen to your engine when you pull the trigger but dont have a nozzle in the wand, doesnt sound like its working near as hard when a tip is in it.
 
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