pressure washer PSI

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  #1  
Old 10-19-02, 05:41 PM
jozly
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Unhappy pressure washer PSI

Hi,
I am looking to invest in a commercial quality pressure washer for
cleaning my pool deck and extensive driveway. I am uncertain as
to how many PSI I should be looking for. Is there a big difference
between a 3600 and a 4000 PSI ?

Thanks
 
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  #2  
Old 10-19-02, 08:24 PM
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jozly:
The pressure rating of the washer you are looking for is only half the story. Possibly more important than the pressure rating is the flow rate at the nozzle in GPM (gallons per minute).
The pressure you are proposing to buy will do a good job of cleaning but at those pressures there is the possiblity of damaging surfaces if not carefull. Also it should be kept in mind that washers in that category of pressure rating require a great deal of care due to the possibility of skin penetration which can cause an air embolism.
My larger washer is 2500 psi at 2.5 GPM. This is powered by a 5 hp Honda gas engine.
This size is effective at cleaning with less risk of damage than using a larger unit.
A pressure rating of 4000 psi at 3.5 GPM would take a 10 hp gas engine to drive.
If you were to purchase a washer that big, you could re-nozzle it to give you 2500 psi at 5 or 6 GPM.
Using a higher flow rate and lower pressure would probably do a better job of cleaning .
 
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Old 10-20-02, 04:17 AM
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Something you might look at that is a disappointment on the washer I bought: The instructions on mine say not to let the engine run for more than a couple minutes without running water thru the pump (and hose). Evidently the pump can overheat and seize up. Someone told me that's typical of the cheaper washers (I paid about $375 at Home Depot). I would appreciate hearing if this is really true. I don't remember having to do that with rental units years ago.

Bruce
 
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Old 10-20-02, 06:26 AM
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Bruce H:
When the trigger is released the pressure increases and opens a bypass valve. This allows water to flow back into the supply side of the pump. The water then goes round and round until you open the nozzle again. This water will then start to heat up from the friction of constantly being recirculated.
This holds true of all pressure washers except electric ones that shut off when pressure builds.
The instructions that came with my 5 hp washer say to "minimize" running the unit under bypass. I've felt the pump after about ten minutes of running bypassed and only noticed a slight warming. I think you would have to get to know your machine.
Another thing that people often overlook is the fact that a lot of washers cannot use hot water. The instructions should state what temperature water their unit will operate with.
A client was commenting on how a local supplier was selling junk washers and that he was on his third unit supplied under warranty.
Hot water was killing his washers.
 
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Old 10-20-02, 06:51 AM
NutAndBoltKing
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Jozly, Greg H hits the nail on the head about the possibilties of doing bad damage to surfaces that you need to clean with the pressure that is generated by the machines, and the water flow necessary to compensate for it, and to do the best job possible.

We have 3 pressure washers for cleaning in my volunteer firehouse. One we bought, two were donated; one by a person who moved away, the other by a local construction company.

The 4000 psi gas powered one will remove paint. It also weighs about 500 pounds! We ruined the sealer on our driveway with it. No kidding.

The other one, about 3000 psi, is 220 volt, and packs a whallop; but in my opinion, the best one, the one that also sees the most action, is the 1500 (approx) psi 110 volt. It has a easily coiled 50 foot hose, (the other two have awfully stiff hoses with minds of their own) and it shuts itself off if the pump isn't being used and begins to heat up. We loan it to anyone who asks and it does a really good job for us.

Good luck!
 
  #6  
Old 10-29-02, 05:28 AM
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jozly,

You have received some very good information here.
You can do the job you desire with the cheaper electric unit mentioned.
There are other considerations when going 'commercial'. You won't find a true commercial unit at Lowes/HD. They don't sell belt driven pump washers with double steel reinforced hoses.

fred
Deck-Kleen Powerwashing
 
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