How much do larger tips reduce your psi?

I use a Simpson 4200 psi 4.0gpm unit the operating psi is probably 3800-3900 i haven’t checked in awhile. If I put on a 8pm tip would that also cut my psi down to 2000? or let’s say a 10gpm tip where do you think I would be?

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You need to look at a nozzle chart and figure it out.



This is a great website I use.

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I’ll help ya out man. Nozzles aren’t categorized by gpm, they’re categorized by the size of the orifice (hole). The PSI delivered through each nozzle is going to change based on the number of gallons per minute your pump can actually push through that hole.

Use this nozzle calculator in the future, it’s the easiest to understand. I use it on a daily basis:

At 4gpm, a size 5.5 nozzle would create 2115 PSI. If you wanted that in a 25 degree fan so you could really wreck some vinyl, you’re looking for a 25055 tip (you can imagine it like 25–05.5)


bringing the orfice size open just a gallon and a half will cut my psi in almost half?

Don’t look at nozzle size in gallon terms. Look at it in pressure. GPM won’t be effected with different nozzles psi will be which is the purpose of swapping nozzles.

It the example above he’s basically saying that a 4 gpm machine using a 5.5 nozzle will create 2115 psi. A 4 gpm machine is going to put out 4 gpm no matter what size nozzle you put in. Put in a smaller nozzle than a 5.5 and your psi will go up. Put in a larger nozzle and your psi will go down. Either way you’re still getting basically 4 gpm. That could change a little if you used a smaller nozzle than you should. You can also sometimes get a little more than 4 gpm when using very large nozzles. Don’t worry about that though.

There’s plenty of info on the forum if you search for it. You can pretty much find anything you need unless you run into a specific problem. This is from a previous post I made to someone else last year. He had a 5.5 gpm machine and 5000 psi so the reply was based off of that. Whatever your machine is you go off of that gpm.

Take a look at the nozzle chart. Keep in mind that you have a 5.5 gpm machine. Let’s stick with one single nozzle on the end of your gun for now. Let’s say you want to use a nozzle that puts out 1200 psi. Look at the top row and follow it to the right until you see 1200 psi. Now follow it down to find 5.5 gpm. (The closest to 5.5 is 5.48). Now follow it to your left to get your nozzle size. So, a #10 nozzle will get you right around 1200 psi.

Let’s say you want a nozzle for you gun putting out 3000 psi. Find 3000 psi up top, follow it down to get to as close to 5.5 gpm as you can (5.63 gpm), now follow it to the left and you find 6.50 nozzle.

Now take the first example but for a surface cleaner with two nozzles. Let’s say you want that same 1200 psi. The surface cleaner has two nozzles so we want 2.75 gpm per nozzle (half of your pump’s 5.5 gpm). Go to 1200 psi in the yellow. Follow it down to find 2.75 or as close to that as you can get. (There’s a 2.74) Now follow that to the left and we get a #5 nozzle. So, two #5 nozzles put out 5.48 gpm and 1200 psi. I know you’ll likely never use 1200 psi for a sc but it’s just an example.

The main thing to remember is your 5.5 gpm. You always want the nozzle or nozzles putting out at the 5.5 gpm so that’s the main thing you’re looking for on the nozzle chart.

Now let’s say you wanted to get around 3000 psi on your surface cleaner. Follow the psi over to 3000 psi. Go down to find 2.75 gpm (half of 5.5). 2.60 is about the closest to 2.75 gpm. If you look at 3500 psi and follow it down to that same row you’ll see a 2.81 gpm. Remember, you’re looking for 2.75 gpm which falls in between 2.60 and 2.81 gpm. Follow that to the left and you get a #3 nozzle. So, if using a #3 you’ll be getting right around 3250 psi. Probably a little less due to hose length and fittings.

The psi of your machine (5000 psi) doesn’t really mean much when looking at a nozzle chart so just forget about it. The only time it matters is if you want to actually put a nozzle on that reaches a certain psi. If you only have a 2500 psi pump you won’t be able to use a 3000 psi nozzle. With your 5000 psi you won’t ever have a problem of not being able to reach a certain psi.

The first two numbers, 25 in this case, is just the degree of the spray. (25 degrees is what’s used for surface cleaners) I normally use a 40 or even 65 degree nozzle when doing deck boards.


The nozzle number does not have anything to do with gallons per minute. It is just a number assigned to it, like a #5 drill bit, or 5 gauge wire.

A 5 nozzle is .057", or 1.45mm
A 5.5 nozzle is .060", or 1.52mm

Varying pressures will push different amounts of water through the same size holes.

Umm, can we put a pin on this post, so it comes up on top for all the newcomers? Or maybe we can just link this post every time this question comes up.

new pic? got bored of the old one?

Marinegrunt has posted that info many times on this forum. I would think that he has it macro’d by now.


Variety is the spice of life.


Oh, so it isn’t methamphetamines?

So I order a few tips and with the 8.0 I’m getting 1500 psi and with the 10.0 I’m getting 1200 psi. according to the chart its no what it’s suppose to be . do they make 25 and 40 degree tips larger than 10.0 ?

they do -

What pressure are you looking for?

I was doing a roof and it wasn’t too bad but I wanted less. I would like all different pressures depending on what I’m cleaning but I would like a few more sizes to get down to 500 psi , 700ish, 900-1000 ish.

dirtboy all those 25 degrees are for surface cleaners right. I know you can use them on your wand tip but do they have 40 degree with all those options ?

You can get any psi and in 0, 15, 25, 40, and 65 degree. You just use a nozzle chart to figure out which nozzle to use. When ordering nozzles the first two numbers are the degree and last the orifice size. So, a 4509 would be a 45 degree with a #9 orifice. With a 4 gpm machine that would put you at about 800 psi. Use the chart below to choose the orifice size and then just add the degree you want first in the number. You’ll then know which tip to order from any online pressure washing supplier.