I have a window cleaning company and I have recently been doing pressure washing. I bought a 4000 psi machine with 4GPM a while back. However, when I read some other posts on this network some said they never go above 2000 psi. I know that the GPM rating has an effect on cleaning but wouldn't the higher psi be good, especially for concrete or brick? I don't quite understand this. Plus, where do you buy a low psi machine with a really high GPM?
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How much Pressure?
- Thread starter bgodley
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Larry L.
PWN TEAM - Moderator Emeritus
WE use different size gpm tips to lower the psi,some things you cann't clean at a high psi.Like different trades use different psi,wood cann't handle a 4000 psi cleaning unless you really know what your doing as to the reason most of use a lower psi.Concrete on the other hand can handle a deep clean at a high psi in most cases.Like your truck it may say it'll do 120 mph but your only allowed to go so fast,more damage at a higher mph if your driving on the wrong road or cleaning the wrong trade at a higher psi.
oguard
New Member
OK here we go... here are the numbers using a standard hydraulic formula.
Flow x Square root of Pressure / 18.92
4 @ 4000 = 4 X 63.25 / 18.92 = 13.37# impact force
2 @ 8000 = 2 X 89.44 / 18.92 = 9.45# impact force
8 @ 2000 = 8 X 44.72 / 18.92 = 18.91# impact force
As you can see each of these units are identical in their number of 'Cleaning Units' but VERY different in their ability to impact the surface being cleaned.
However, 8 GPM is at the upper end of the readily available source of supply.
Now if we use your 4 @ 4000 unit and lower the pressure to 3000 PSI your impact force drops to 11.58#, at 2000 PSI it is only down to 9.45# or the same as a 2 @ 8000 unit.
Flow rules most every application, flow is directly related to horsepower, more of one needs more of the other.
Pressure is the most potentially dangerous as over 3500 PSI you need special fittings, hoses, guns etcetera that cost more. You should be wearing armour as well at 4000 PSI or above. 4000 PSI will strip paint from concrete or metal, break glass or cut off your toes.
The appropriate application of chemical, temperature and technique are more valuable than pressure. More flow gives you more opportunity to apply soap so you get longer dwell time, rinses faster and poses minimal physical danger.
As Larry L stated only use larger orifices to lower pressure, never use a smaller orifice than supplied by the manufacturer. Do not adjust the unloader as it is a primary safety device and will wear prematurely causing failure and needless expense.
Hope this helps? Cheers.
Flow x Square root of Pressure / 18.92
4 @ 4000 = 4 X 63.25 / 18.92 = 13.37# impact force
2 @ 8000 = 2 X 89.44 / 18.92 = 9.45# impact force
8 @ 2000 = 8 X 44.72 / 18.92 = 18.91# impact force
As you can see each of these units are identical in their number of 'Cleaning Units' but VERY different in their ability to impact the surface being cleaned.
However, 8 GPM is at the upper end of the readily available source of supply.
Now if we use your 4 @ 4000 unit and lower the pressure to 3000 PSI your impact force drops to 11.58#, at 2000 PSI it is only down to 9.45# or the same as a 2 @ 8000 unit.
Flow rules most every application, flow is directly related to horsepower, more of one needs more of the other.
Pressure is the most potentially dangerous as over 3500 PSI you need special fittings, hoses, guns etcetera that cost more. You should be wearing armour as well at 4000 PSI or above. 4000 PSI will strip paint from concrete or metal, break glass or cut off your toes.
The appropriate application of chemical, temperature and technique are more valuable than pressure. More flow gives you more opportunity to apply soap so you get longer dwell time, rinses faster and poses minimal physical danger.
As Larry L stated only use larger orifices to lower pressure, never use a smaller orifice than supplied by the manufacturer. Do not adjust the unloader as it is a primary safety device and will wear prematurely causing failure and needless expense.
Hope this helps? Cheers.
Mikespowrwash
New Member
I have a 3000 psi 5gpm machine hot water. I rarely ever clean anything above 2000 psi even concrete and brick. I use a duel lance set up so all I have to do to lower pressure is twist the handle slightly. Like Larry said, higher psi higher damages poissible. I use duel lance and hot water 25 degre tip on almost all my cleaning except wood where cleaning is done with cold water.
Mark
Moderator / Sponsor
Welcome To PWN
Brian,
Welcome to www.Powerwashnetwork.com
it was nice chatting with you today.
Don't hesitate to ask questions.
Brian,
Welcome to www.Powerwashnetwork.com
it was nice chatting with you today.
Don't hesitate to ask questions.
