Water Pressure on a Outdoor Hose / Length vs. ID

[Chefwong]

What effects the hose pressure in a outdoor hose (aside from the physical fittings).

For example, great pressure with the 3/4 hose.
Needed some more length. Added another 25 foot 3/4 hose - definately noticed a slight pressure drop.
I don't know if the ID of it' was the same but one would presume yes.

 

[Gary Swart]

You had no pressure loss, you had a slight loss of flow due to friction created by the added length of hose. This is why folks who have a long distance from their water source require a larger pipe.

 

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[Chefwong]

Thx Gary.
There is a 1/2" Tee to the garden spigot.

If I either upsize the entire hose to 1" or the latter, meaning, leave the 3/4 GH alone but from the T, upside that run to 3/4 to the bibb, will I see a difference in WP ?

 

[Gary Swart]

Chef, pressure is not the same as flow. Pressure is determined by the source, usually the city water main. It can be lowered with a pressure regulator is it is too high, but it can not be raised. The 1/2" tee would lower the flow somewhat, but will not change the pressure. Going back to your original question, if you put a pressure gauge on the end of the first section of hose, it would indicate the pressure. If you then add the additional length of hose and measure the pressure at the end of that hose, guess what. It will be exactly the same. What will change is the amount of water in a given period of time that will come out. That is flow. The added length of hose will affect the flow because of friction.

 

[Jadnashua]

There are two measures on pressure...static (no flow) and dynamic, with flow. Static pressure will stay the same whether you have a fire hose or a soda straw. Dynamic pressure will vary based on the desired flow rate, the diameter, and the length. The longer the run and the smaller the diameter, the greater the dynamic pressure drop will be from the friction (and that also results in lower flow). A restriction will affect the friction and thus the dynamic pressure drop, but a short length has less effect than a longer one. The Bernoulli principle comes into effect...the fluid will speed up through a restriction, and slow back down when it opens up. Depending on the shape and length, and the resulting turbulence, you may not see much difference. There are various calculators that will tell you the pressure drop from friction on a pipe, and the effect of fittings and changes of direction. The math can be messy, so a well-done calculator is the best way to come to a decent estimate unless your math skills are current and somewhat advanced..

 

[Chefwong]

Interesting read on flow. Regardless of pipe size behind the bibb, if I upsize the entire hose run, I would see a better ~flow~

 

[Reach4]

Interesting read on flow. Regardless of pipe size behind the bibb, if I upsize the entire hose run, I would see a better ~flow~

Yes. You would also see better *pressure* at the business end while using water.

 

[hj]

You can affect "residual pressure" at the end of the hose. With on open hose it will be minimal but maximum volume. Put a restrictor on the hose, such as my son's pedal fire truck hose, and you will be able to shoot the water over the neighbor's house but with little actual volume.