I live in a 5th floor of a building that doesn't have strong water pressure. I remember that many years ago a cleaning group was going to pressure-wash the exterior of the building, but couldn't because, supposedly, the water pressure wasn't strong enough. I wasn't there at the moment; a neighbor told me this.

So yesterday I saw a 1,450 PSI electric pressure washer for around $80, and I was considering buying one to clean the rooftop. But now I'm reconsidering.

So, my question is, does low water pressure actually affect the functionality of a pressure washer?

What my neighbor told never made sense to me. From my understanding, the purpose of a pressure washer is to work with low water pressure.



You need at least the same flow rate out of the hose that the pressure washer uses. look at the GPM (Gallons per minute). With the hose on the roof, run the hose wide open for a minute or 2 so you will have the true flow rate. Then fill a bucket and time how long it takes divide by the size of the bucket if your unit uses 2.5 gallons per minute, a 1 gallon bucket would need to fill in 24 seconds, 12 seconds for a 5 GPM. You don't want to starve the pump or it will damage it. Many contractors use 5 GPM @ 5000 PSI and larger units. 1450 is probably 1.8-2.5 GPM from the units I have seen. If you have slightly higher than the flow the machine needs you should be good. There are also inline booster pumps with standard hose fittings that could be used at ground level to increase the pressure (Running on 120V) these can be expensive for a good one.

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  • So when the group said that they couldn't use the pressure washer in the building, they actually meant that the GPM from our hose was lower than the GPM from their pressure washer? – rbhat May 6 '16 at 19:27
  • That may have been the case my 6500 PSI unit shuts down if the pressure is not enough to supply the pump. – Ed Beal May 6 '16 at 19:52

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