"Gunner Asch" wrote in message
...
On Mon, 20 Sep 2010 11:17:12 -0500, "Pete C."
wrote:


Gunner Asch wrote:

On Mon, 20 Sep 2010 07:32:29 -0700, "Steve B"
wrote:

Does a power washer have to have pressurized water on the inlet, or
will it
draw from a tank source?

Steve


Most will draw from a tank, many older models do.

The big issue is making sure they get primed. Hence the tank needs to be
a bit higher than the pump.

A tank source higher than the pressure washer pump *is* a pressurized
source.

True but most folks dont consider .5psi to be "pressurized" but your
meaning is true indeed.

Most pressure washer pumps will not give you any reliable suction lift,
and can be damaged if they cavitate / run dry. As a general rule, if you
want to use water from a pond or the like, you will need to use a second
"charge" pump to get the water from the pond to the pressure washer. A
filter is also a good idea.


Very true.

IIRC ...................

Salt water is .445 psi per foot of head.
Fresh water is .443 per foot of head.

1atm of air at sea level is 14.7 psi, not taking into account barometric
pressure variations.

At 33' of diving depth in salt water, it is 14.685 plus the 14.7, making it
very nearly 2 atmospheres, or 29.4 psi.

If you are using a gravity feed, the water source would have to be
57.11060948 feet higher than the power washer to provide 40 psig to the
washer, and that is allowing for the 14.7 psi for normal atmospheric
pressure.

So, it could actually be done with a water source about 60' higher than the
power washer.

I was just unsure if the power washer had any suction capabilities, or
needed a positive pressure feed. At those conversion factors, and allowing
14.7 psi for sea level pressure, it would take another 25.3 psi to just keep
up with it.

Or am I miscalculating, and it would take the full 40 psi?

Steve

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