Lowering pressure with tip

[JFife 14]

I sure hope someone can give me an answer to this question which has been alluding me for years now.

I've heard people say they can lower the pressure at the tip with a bigger orifice. Obvious, right?? You put on a soap nozzle, and you get a light spray. But I'd like to get something around 1000-2000psi, and i've heard people say they can do that with a bigger tip (per envirospecs chart). I use 3000psi, 4gpm coldwater, and i've tried following the chart to lower pressure, to no avail. Is it possible that I am lowering the pressure, and just cant tell the difference??? I don't think that's it. I'd expect to be able to hold a wand straight up above my head pointed out with 1000psi and it not blow my arm back. Am I wrong?? Can anyone think of a solution to this, or something I am not doing correctly???

To reiterate, my point is that I can put on a 40deg. tip which should produce 3000psi, and I cannot tell the difference in a 40deg. tip that is larger and is supposed to produce 1000psi.

jon

[PressurePros 249]

The problem you are experiencing is probably because of the type of unloader you have. I am guessing it is pressure actuated, which means regardless of your final pressure you are going to get that 3000 psi burst. I switched over to a a flow actuated unloader and haven't looked back. The difference is dramatic. No more spikes to gouge wood or loosen siding. The chart is confusing at first. you follow the gpm of your machine to the desired pressure you are looking for and it will tell you which nozzle to use. On your machine a number 8 will get you to the pressure you seek.

[PLD 14]

Yes, I use a pressure unloader and the initial blast is substantial. If you want to see a difference, use a 40040 and a 40100 back to back. You'll be able to tell a difference in force at the surface. I'm using a 3500/4 and when I'm paying attention I can tell the difference in a 40080 and a 40100 just by feel (working feel, not holding feel).

Also, keep in mind mind that the force on your arm is related to pressure and flow. If you open the orifice to half the pressure, and double the flow, the kickback will not decrease by half.

[Russ Johnson 141]

4 gpm:

#4.5 = 3000 psi

#6 = 2000 psi

#8 = 1000 psi

[Beth n Rod 1,279]

Bingo. If it was flow actuated, you would get the nice build up. I like a flow actuated unloader since I don't like the feeling of ripping off my shoulder. But, the pressure actuated ones (big green spring) last longer. (based on expereince and on what others have said here)

Remember that you are getting the same GPM through the tip regardless of the orafice, so it's not like it looks like it is less if you know what I mean, in fact, it may look like more, since more water flows thru....

Beth

p.s. I love the soap tip.

[PLD 14]

Remember that you are getting the same GPM through the tip regardless of the orafice

Are you certain about that? I understand that the pumps are positive displacement which supports your info. My schooling concurs as well.

BUT, HydroTek prints right on their machine's control panel that a 8.0 tip uses 8gpm, a 6.0 used 25% less water, and a 4.0 uses half the water. They even label the 4.0 as a "water saving" nozzle.

If you are correct, forget what I said about volume and kick. If the volume remains the same, reward force varies with exit velocity (i.e. nozzle pressure)

[JFife 14]

So are you guys suggesting that a different unloader will reduce my pressure?? Honestly, i don't really know what "flow actuated" or any of that stuff means. I usually buy cheap machines and only use them about 200-300hrs. each a year. So can you recommend an unloader to me that might solve this problem?? I know there has to be an easy fix, I've worked side-by-side with Guntars (grime member) and he uses a hot machine from Delco, and he can spray with lower pressure, whereas if i put his wand on my machine, no difference. thanks for the help,

jon

[VanDiesel99 14]

The difference in pressure sometimes isn't very apparent due to the fact that the same amount of water is coming out. Its easy to think that since your putting out about a 1/3 of the pressure, then the spray will be noticeable "lighter" for lack of a better term. The only noticeable difference I can tell is that the water comes out at a higher velocity and turns to mist more than at a lower psi. Get a pressure gauge and check your PSI with that. The pressure-actuated unloaded only affects that initial burst that comes as soon as you hit the trigger.

[JFife 14]

aaaahhh, that makes sense now, I have k7 unloaders on my machine, and that is what they do, slowly build. The gauge is a good idea, I'll try that and see, maybe I am using less pressure. thanks again guys,

jon

[Bates 14]

Hydraulics 101

Smller hole in the tip makes more pressure, larger hole makes less pressure if everything else is constant (pump displacment)

Flow sensitive unloaders or pressure sensitive unloaders are both attached to apump, the pump will only move X amount of water (all thing being constant), reduce the size of the tip and the pressure increases, enlarge the tip and the pressure decreases, the flow amount obviously increases with the increase in size of the tip size.

The 'flow charts' are based on the amount of water that will flow throigh a fixed orifice at a given pressure. They do not take in account pressure drop due to hose, temperature etc. Basicly they charts are a guide, they are pretty accurate, but still a guide.

My experience is typical soap injecters (downstream) start flowing soap with a '20 tip size on a 3000 or 3500 psi unloader machine that flows around 5 gpm, which means the soap injecter starts sucking soap around 250 psi, and would also suck soap with a '40 tip but the pressure would be around 70 psi. As the tip size increases the pressure drops if the flow remains the same.

Good Luck

[Beth n Rod 1,279]

BUT, HydroTek prints right on their machine's control panel that a 8.0 tip uses 8gpm, a 6.0 used 25% less water, and a 4.0 uses half the water. They even label the 4.0 as a "water saving" nozzle.

That is for a dual wand system, and you are changing the amount of water going through one gun. If two guns are in use, you split the GPM. If one gun is in use, you get all the GPM's. Hope this helps.

Beth

[Beth n Rod 1,279]

Jon,

It's not the gun, it's the tip. The tip needs to be the right one for your machine. Look in just about any catalog for a tip (nozzle) chart. Find the GPM on the chart, then go to the PSI you want to drop to on the chart, and in the grid it should tell you what tip size you need.

Beth

[JFife 14]

Beth,

thats what I mean, I've done that, and can tell no noticable difference from a #4 tip to a #10 tip (all else equal). I'm going to get a pressure gauge and see what it says, perhaps you just cannot tell the difference due to the additional water output.

[Aplus 525]

Jon,

There should be a noticable difference in the kick from a #4 to #10, regardless of what type unloader is used. Maybe you're just stronger than you thought you were........

[PressurePros 249]

Tony, I respectfully disagree. The pressure builds in the hose. Even without a nozzle a pressure actuated sytem will give a short burst when the trigger is pulled.

[tropical wave 22]

Jon,

There should be a noticable difference in the kick from a #4 to #10, regardless of what type unloader is used. Maybe you're just stronger than you thought you were........

too funny !!! where it is really noticable is if you have a blue or yellow extension wand......put in a #4, extend the wand and pull the trigger (and hang on!) the noodle will bend like a banana, then try it with a #8 or even a #10...VERY noticable difference in the pressure......the wand will pretty much stay put...(and you'll get just as wet underneath it!!)

[Aplus 525]

Tony, I respectfully disagree. The pressure builds in the hose. Even without a nozzle a pressure actuated sytem will give a short burst when the trigger is pulled.

If you're speaking of the initial burst that a pressure unloader provides, as opposed to the gradual ramping up that a flow unloader provides....true.

What I'm saying is that with either style unloader, there should be a noticable difference in the "feel" when the trigger is squeezed and the water is flowing.

With a higher # tip, the flow is the same, but the psi is reduced. It's the psi that gives the big thrust feeling.

I still think Jon may be stronger than he thinks, therefor he can't tell the difference......:)