Question about water pressure concepts

Old 10-04-19, 07:34 AM
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Question about water pressure concepts

I know on an adjustable garden hose nozzle, when you make the spray into a beam / narrow, it get's 'stronger'.

I recently bought an adjustable nozzle and it came with a free all brass nozzle that just has a small hole in it. something like this:

it cleans things really well, at the expense of the size of the area it covers (smaller than a pencil).

I have something like 125PSI house pressure at the outside spigots. And 3/4" lines? so something like 10 GPM?

The pressure of the water coming out of that nozzle - is that 125 PSI? and lower flow than the 10GPM? It doesn't amplify the PSI, right?

a pressure washer increases the pressure of the water coming out and is also much less than the 10GPM coming into the pressure washer, right?

These nozzles don't compare to a pressure washer in strength I would assume?
Old 10-04-19, 08:54 AM
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Bernoulli's principle says that when a fluid flows through a constriction in a pipe (i.e., the orifice in a nozzle), the fluid gains velocity but loses static pressure (venturi effect). Water emerges from the nozzle with less pressure than it had in the garden hose, not more.
Old 10-04-19, 09:20 AM
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Fred is right. A nozzle cannot create pressure and forcing water through the tiny orifice creates resistance which further reduces pressure in addition to Bernoulli's affect.

Yes, a pressure washer increases the pressure of the water with a separate pump. The gallon per minute thing has more to do with your water supply and the pressure washer. There are pressure washers capable of pumping much more than 10gpm while most residential units only move 2-5gpm.

No, a spray nozzle on the end of garden hose doesn't compare to a pressure washer. After all, a pressure washer has an additional 5 hp behind it or whatever power your pressure washer is.

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