1/2 inch pressure hose

Pat Norman

New member
Well recently when I installed a new K7 unloader, I also installed a permanent pressure gauge between the pump and unloader. In the past I've always used a temporary quick connect gauge at the reel and at the end of the hose to occasionally check my pressure. So now I am really starting to understand the back pressure caused by 200 feet of 3/8 hose. When using a #60 orifice with my 8gpm x 3500 psi machine creates 2900 psi at the pump and 1000 psi at the gun (when using a 2.1 injector). Without the injector the #60 creates about 1800 at the pump and 1000 at the gun. With an #8.5 orifice and no injector I am getting 3500 psi at the pump and about 3200 at the gun.
So here is my question, if I change to say 170 feet of 1/2" hose and put a 30 foot "tail" of 3/8" hose so that the end won't be so darn heavy will I gain any performance in psi, gpm, better soap draw (I draw pretty darn good right now using the 2.1 injector), less lag-time in the K7 unloader giving me pressure ? Seems like the combo of 1/2" with a 3/8 tail might be best of both worlds.
 
I think pressure loss is the word you are looking for using a 3/8 inch hose running high volume will cause pressure loss but i dont think back pressure is an issue.Use all or none when you put that tail of 3/8 you will bottle neck what you have and force it through an you will be back at square one with pressure loss.
 
Hose pressure loss is figured by length of hose. The tiny little opening at the end really creates backpressure so I think 'necking down' at the end will not affect pressure loss as much. How long a leader hose you can get away with, I don't know. The single wire 1/2" (3000 psi) is not too heavy.
 
With 8gpm you are looking at about 45psi pressure loss per 100' of 1/2" hose vs. 300psi pressure loss per 100' of 3/8" pressure hose.

A 30' whip hose or extension will not get you far in each direction and you will still have to tug that heavy 1/2" hose to an extent.

I use the 1/2" pressure hose when surface cleaning but for house washing (soft washing) I use the 3/8" pressure hose as I am lowering the pressure anyway for downstreaming and have had no issues washing houses, 2nd story houses and 3rd story apartments/hotels.

What are you washing mostly? There are solutions to what you are wanting to do, let us know so we can help you.
 
You would gain flow/volume. I believe the back pressure is more from the weight of the water over the distance of hose travel. Which leads me to believe moving more water over that distance would create more back pressure (depends on whether it is traveling up or down hill). You could increase the chemical induction by pumping into the injector though.

Someone correct me if I am wrong here...
 
Hose pressure loss is friction loss from the water rubbing on the hose I guess.
 
I think Chris said it best if you are cleaning at full on no holds bar remove the injector and put the 1/2 inch hose on and wash away.
 
My other concern is that an equipment dealer many of us know says that an 8gpm pump needs 1/2" hose in long lengths. He keeps saying premature wrist pin failure, need it with a K7 yada yada yada.
 
If you're running 200 - 300 feet of hose, using 1/2" for the first 150 - 200 feet and then 50 - 100 feet of 3/8" at the gun will help the flow.
 
Well recently when I installed a new K7 unloader, I also installed a permanent pressure gauge between the pump and unloader. In the past I've always used a temporary quick connect gauge at the reel and at the end of the hose to occasionally check my pressure. So now I am really starting to understand the back pressure caused by 200 feet of 3/8 hose. When using a #60 orifice with my 8gpm x 3500 psi machine creates 2900 psi at the pump and 1000 psi at the gun (when using a 2.1 injector). Without the injector the #60 creates about 1800 at the pump and 1000 at the gun. With an #8.5 orifice and no injector I am getting 3500 psi at the pump and about 3200 at the gun.
So here is my question, if I change to say 170 feet of 1/2" hose and put a 30 foot "tail" of 3/8" hose so that the end won't be so darn heavy will I gain any performance in psi, gpm, better soap draw (I draw pretty darn good right now using the 2.1 injector), less lag-time in the K7 unloader giving me pressure ? Seems like the combo of 1/2" with a 3/8 tail might be best of both worlds.

contemplating 1/2" huh?

I agree with what Chris C wrote , it depends on what you are washing, if you dont need the full pressure at the tip (example for cutting action) or at the surface cleaner to get better arm rpms, or dont run long lengths (150ft or more), or your pump can hit at or over 4000psi, no need for 1/2.

This is why I am now of the opinion (since my 3500psi machine) that 4000psi pumps are better choices for concrete cleaning, in the event that you ever have to run extra long lengths of hose you can still have a respectable impact/flow. (I run 1/2" hose with 3/8" ends)


The other thing that I have not seen measured is the pressure loss in trigger guns and 1/4" lance, I am thinking this would be a moderate suprise.



I am currently in a similar hose dilemma, but with a different type of hose, if to use the industry standard 2" vac hose or bigger, wondering whats the suction loss running 300 to 400 cfm in long lengths of 2" hose.


Anyone find a chart with suction loss in air vacuum hose?
 
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