Garden Hose Sizes

[Bandit Bill]

I just bought a pressure washer and I'm having a difficult time understanding if buying a larger diameter garden hose will actually make any difference. It seems to work just fine with the 1/2" hose that I have.
I tested the hose and I'm getting around 3.5 GPM. The pressure washer requires 2.8 GPM. The manufacture however recommends a 5/8" hose as a minimum.

Anyhow, I'm having a difficult time wrapping my head around the fact that a bigger hose is going to deliver more water. How does this work when the outlet from my hose tap is smaller than 1/2".

Has anyone actually used a larger diameter garden hose and seen a big difference in day to day use?

[fuentecigar]

It follows Bernoulli's principle which describes the flow of an incompressible,
non-viscous fluid during non-turbulent flow.

p + dv^2/2 + dgy is constant.
p is the pressure (higher pressure means higher energy per unit volume)
d is the density (kg/m^3), v is the speed of the fluid, y is the height of the fluid (water tower).
g is the acceleration due to gravity (9.8 m/s^2 = 32 ft/s^2)
dv^2/2 is the kinetic energy per unit volume
dgy is the gravitational potential energy per unit volume.

Assuming you are using a municipal water supply, the water pressure is determined by the height of the water tower with the greatest amount of pressure being at the tip of the garden hose (no matter what the size). Notice that if the nozzle is of smaller diameter, the velocity of the fluid must increase, since the fluid is incompressible. Then, since the kinetic energy term increases and assuming the height of the tower does not change, the pressure must decrease. The pressure of the water will decrease as it flows through the hose due to friction of the inner walls on the passing water. The larger diameter hose will flow a greater volume of water but it will be at relatively the same pressure. The reason the manufacturer is asking you to use a larger diameter hose is to satisfy the volume demand. The pump on your washer is going to satisfy the pressure aspect by multiplication. The greatest enemy of any pump is cavitation (asking for a greater amount of fluid than can be supplied). They are probably erring on the side of caution.
I hope I haven't muddied the "water" too much.
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[philiparcario]

if it is fine don't replace the hose. a larger 5/8 will deliver more gals per min then a smaller hose. if your pressure washer sputters change hoses.
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[Bandit Bill]

Thanks for the replies.

The thing seized up on me the other day. It was only it's third use. I'm glad I bought it from Costco. It was $400 and it had a Honda engine. I'm not sure if the pump seized up or the engine. I can't pull the start cord any longer.

I sure hope it was getting enough water

[Smithcraft]

Sounds like oil might have been more of a critical component in that equation.

SC
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Make sure it has pins!

[Bandit Bill]

[fuentecigar]

It would be my guess that the pump did, in fact, cavitate and seize. If you have any trouble on the warranty, the pumps are not that hard to take apart and repair. Probably less than 10 parts in the pump section, altogether.
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[Bandit Bill]

[fuentecigar]

Electrics can be pretty steep. Karcher's and Bosch come to mind. I'm not sure if the Bosch is currently still in production, though. Models producing heated water run up usually over $1000.00 USD. If there is a Canadian version of Home Depot; it might not hurt to check there. Most of the ones that are commonly seen, down here, are the version that you have. A Honda engine hooked to whatever brand of pump. For $500.00 you should be able to get a very serviceable unit. Finding it will be the issue. Best of luck.
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[graceangela9]

[billb]

A few years ago (before Sears went bankrupt)
I had bought a Sears brand pressure washer.
It was the second cheapest model that came
with a free kit. Bought seperatly it would have
run something like $200 USD but together on
sale it was something like $129. The kit contained
a cart with wheels, various sprayer attachments
as well as the hose that you attach to your faucet.
The hose BTW was very thin. Something like
half an inch O.D.

It could take the paint off of your car if you
weren't careful. It was 110 volts. Sorry, don't
remember the model number. My neighbor
borrowed it to spray his sidewalk clean.
Worked great.


I guess what I'm saying is don't get fixated
on the hose diameter.
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