Nozzling the Power Washer: explain to me why & how it works

Nozzling the Power Washer:
explaining why & how it works


I have been a bit under the weather here lately so to keep busy I thought I would put in a bonus entry.  The busier the week the less time I have to write here. I have written about nozzles if you need to review please refer to the entry: http://cleanedbypete.blogspot.com/2012/12/nozzles.html

I was asked to try to explain nozzling a power wash again. Had a question that need to be clarified. Since they did not follow what I was trying to convey on a few points. I'll try it again hopefully this time I can explain it better. Sometimes you can say something that makes all the scene in the world to you but others may not follow the point because of the writing.

We know that a pressure pump is employed to do two functions in the standard power washer. The first is to pump water the second is to put that water under pressure. We then get our ratings of psi and gpm. If for the sake of argument we are pushing out 4 gpm @ 4000 psi we can change one thing here that would be the pressure. If we have a constant water supply we will be putting out the 4 gallons a minute no matter what we do. We can take out the nozzle it will put out 4 gpm, we can put in a zero degree nozzle the same 4 gpm. This remains the same what ever the pump is capable of, it will remain the same as far as output, as long as the water supply that feeds it is up to the output level or greater. We can try to put in 8 gallons of water into the pump but it will still only pump out the rated gallons.

I would like to mention you can and are able to change this output on a pump by over-driving or under-driving it. This is achieved by changing the pulleys on the motor and or pump. Over-driving it we will turn the pump faster thus moving more water through the pump, under-driving the pump it will produce less speed thus less water will move through it. If this seems to interest anyone let me know I'll try to put together an entry on it.

Now that we have the constant water volume or the gallons per minute is static. By changing the nozzle we can change our pressure. Someone out there right now is saying I can change the pressure by screwing out the unloader that is all it takes. While this is true to a certain point once your unloader is set for maxim output it should not be touched!!!!! Let me repeat this once your undoader is set to the maxim output it should not be touched. I have most of my unloaders  set to the maxim output and then I will lock them down, inside the knob with a nilock locking nut, being able to turn the knob at maybe a half turn to free up the unloader if it sticks. This way it is non-tamperable if someone walking by turns the knob. 

This leaves us only one way to now change the pressure that is being developed in the pump is "nozzling". Our pump should be using a certain size of nozzle let just say for this case we are using a #5 nozzle this is the size of the hole in the nozzle. If we use this #5 nozzle we will be putting out our recommended pressure. No matter if we use a 0 degree tip or a 40 degree tip we will be changing the fan pattern but the pressure will remain the same if we use that #5 tip size. Use your nozzle chart and find what size tip you need to use and you will have your maxim pressure.

Now for us "house washers" we would like to have less pressure sometimes like when we wash vinyl or soft woods as well as paint. How? you are asking well we use an over sized tip we can use say a #40 or #50 we can have the advantage of changing the fan pattern to. Getting the cleaning power of a larger stream of water moving that dirt off. We are always cleaning with friction water moving over the dirt partials the force of the moving water is what really cleans. The fan pattern will not change your pressure but it makes you able to contain the stream for a further reach or to widen it for a larger rinse area. Let us look at it this way on your garden hose if we block off part of the end of the hose you can make the water squirt out further the smaller we make end of the hose the more pressure it has. A fire nozzle has a relative small hole in comparison to the size of the hose. If we use just the end of the hose the water comes gushing out but with out alot behind it. Any time we move up in the nozzle size by enlarging the hole will allows us to still have the cleaning power of the volume of water at a lower pressure.

When I first started there were not all the shops and supply houses out there and it was more of trial and error to find out what worked to lower the pressure. I  would used worn out nozzles or would go in and buy a fist full of correct size nozzles and start to drill them a bit larger with a numbered set of drills. Drill it out try it see if it was what we needed. On a side note, you notice these nozzles wear out sometimes you think you're loosing pressure in you machine but it could be the water has bored out the hole in the nozzle larger. The higher the flow the more the pressure the quicker the wear on the nozzle. Now as we drilled and tested we would find the hole size "oversized nozzle" that worked for what we were doing. You know when big is too big because it will have reduce the pressure enough to draw soap or cleaner. Now this is nozzling in it simplest form. Simply letting more water flow out the nozzle by making it bigger in diameter and in the process we also soften up its' cleaning effect on the surface we need to be more careful with. Surfaces as vinyl, wood, plastic, soft rock or any other substrate that cannot take high pressure. We here at Cleaned by Pete  smaller washers for certain jobs that will require less pressure. In using less pressure and gallon flow we also we not be able to reach and clean higher areas as two and three story houses. Nozzling the large units is what works for us.

Play around with larger sized nozzles and find what works for your washer and how you wash. Always go bigger the bigger you go the less pressure your washer will develop. You will want the greatest flow with out drawing soap. You are fine tuning your machine what works for another may not be optimal for you. Never go smaller than your recommended size unless you have a gauge and a special gun with pressure pop-offs to check things out. If you do not you may need to see your power washing repair shop to set the unloader and find the  approbate size nozzle. Please let me know if I need to try again of it this now make more sense. The power washer creates the pressure the nozzle just controls it.

Just a tip if you would like to try to see what may work for you to help to quickly get a range of what size tip you would like and what works, pick up a #30, #40 and a #50 all in a 0 degree and give them a try. If you draw soap or cleaner "downstreaming" you can use that tip shoot soap but you know what range your in for rinsing. Once you find the best size you then can get in to the fan pattern from 5 degrees to 25 degrees again what works for you.

Cleaned by Pete @ 417-459-7869 in Springfield MO, wants to thank you for reading and supporting our blog if you have a free moment please share it with your friends or other people feel free to post a link to the blog. As always thank you for your support.