PSI and GPM???

[Justin]

OK, This might seem like a stupid question but I have asked a few suppliers and keep getting different answers.

Say I buy a 8GPM 5000psi machine. I want to run at 2500psi while washing the house but switch it to 3500psi while washing the driveway then 5000psi while washing the paint off their tin shed. I want to keep the 8GPM flow rate the whole time.

It makes sense to me that I achieve this by changing tips. I have been told that you lower the RPMs adjust the unloader etc. etc.

What is the proper way to do this without damaging my machine?

Thanks,
Justin

[Guy B]

Justin, why do you need a 5000 psi 8 gpm unit? I may be wrong but a unit like that would have to be custom made. You should do fine with a 3500 psi 8 gpm unit. But to answer your question, you can achieve the results you want by changing the tips. Larger tips will decrease the psi but still give you max flow, smaller nozzles will increase psi and decrease gpm. I have an 8 gpm unit and use less than 1000 psi to wash houses, concrete 3000 psi and hot water. Just my .02, good luck!!!

[Justin]

Sorry, I wasn't saying I need or want a 5000psi machine I was just using it as an example. Thanks for the answer.

Do you guys know where I can find a chart on tip sizes pressure and flow rates.

[Guy B]

Do a search here or do a google search on Pressure Washer Nozzle Chart.

[John-Clean County PW]

Do a search here or do a google search on Pressure Washer Nozzle Chart.

Its all in the tips.

[Aspen Contractors]

Justin,
I would never touch the unloader. You will never get it set back to the same setting. I was told the same when I first started. Just change the tips. Its a whole lot easier to do anyhow...

[GMack]

Guys,

I was wondering the same thing months ago and never really figured it out. Somone was telling me that the different tips (red, yellow, greeen, white) gave different psi's. I argued that, technically, the psi would be the same holding the wand point blank to the subtrate, that the difference in psi is acheived becasue the different tips are creating different angles so that from six inches away with the pressure is spread over more or less of an angle. Is this right, wrong, or somewhere in between?

[Tim Fields]

Do you guys know where I can find a chart on tip sizes pressure and flow rates.

http://www.barens.com/cgi-bin/calc Is a tip calculator that may be of some help. I have also seen a table from Sunbrite that was good.

http://lib.store.yahoo.net/lib/sunbrite/Chart Is another one in chart form.

[John Orr]

Guys,

I was wondering the same thing months ago and never really figured it out. Someone was telling me that the different tips (red, yellow, green, white) gave different psi's. I argued that, technically, the psi would be the same holding the wand point blank to the substrate, that the difference in psi is achieved because the different tips are creating different angles so that from six inches away with the pressure is spread over more or less of an angle. Is this right, wrong, or somewhere in between?

The color of the tip only denotes the spray angle. Red = 0 deg, yellow = 15 deg, green = 25 deg, white = 40 deg. The psi is regulated by the orifice size for any given tip. A typical white tip for a 3500 psi/4 gpm pwer would be 40040 or possibly 4040. The first 40 is the angle and the last numbers are the actual size of the tip - in this case 04.0 or 4.0. Tips come in many sizes, in fact, many times I will use a 40120 (40 deg and 12.0 size) to lower the pressure without lowering the gpms. Hope this helps.

[PressurePros]

Every change in pressure is done with your nozzles. There is rarely any reason to adjust your engine's throttle or the unloader.

Nozzle changes affect two things.. pressure and spray pattern.

Spray pattern (the different colors on plastic nozzles): The width of the spray that leaves the nozzle. Its measured in degrees. Its a double digit number and is the first thing to read when eyeballing a nozzle. 4015 (40 degree spray pattern, #15 orifice)

Pressure: This is affected by the size of the orifice. The larger the number, the larger the orifice. 4015 (see above) Note: I am indicating a #15 orifice. One could also read that as a #1.5. The technical designation should be 40150

Here is a chart. Some charts are confusing, This one is easy to read. To make it easy, look at the column that starts 2.0. That column is your gpm. If I wanted 3500 psi, i would need a #2.0