Is it at all possible for a normal garden hose to develop head pressure? And where would such a head be?
“Head pressure” typically means the energy built up behind an outlet, such as the end of your garden hose. For example, if your water system uses elevated tanks, it’s likely that your hose has a couple hundred feet of static head sitting on top of it.
Is that what you’re talking about?
I don’t know, I just read on another Website that someone asked that sort of question, and I had no idea what they were talking about…so I asked the question here, because I’m sure you all would be able to decipher and answer the query.
In engineering terms, “head” is a measure of pressure. In the U.S., head is measured in feet and is related to the principle that a water tank or other water source 15 feet above the outlet will produce roughly 15 ft of “head” minus the losses due to friction and constriction. Head can take the form of pressure or velocity. That means that 15 ft of “head” can pump water up to a height roughly 15 feet above the source.
Head pressure can also be converted to pounds per square inch.
A column of water 1 foot high exerts 0.433 psi at the bottom.
A water tank 200 feet tall would have 86 psi water pressure at the bottom.
a garden hose will have head pressure in it if you want to get water out of it.
if the hose had water in it (ends could be capped) and you elevated one end of the hose relative to the other then it will create head pressure.
It doesn’t really need to be capped to have head. If water is flowing, there is an energy differential between the water on one end and the other.
Head is always zero at the outlet/nozzle of the hose, where the water pressure is exactly equal to atmospheric pressure. From there, you can work backwards depending on the restriction in the line (due to valves, orifices, elbows, kinks, or just hose length) and the flowrate going through it, until you eventually reach water main pressure or whatever pump or gravity well pressure you have at your source.
There are many units which are in common use to describe the physical observation called “Pressure”. We frequently say there is 14.7 pounds per square inch (psi) of pressure from the weight of the atmosphere at sea level. This pressure will raise a column of fresh water 34 feet in an evacuated tube, so 34 feet of head pressure = 14.7psi = one atmosphere. In a manometer, which is sometimes used to measure pressure, an evacuated tube is immersed in a pool of mercury, which will rise to a level of slightly less than 30 inches (or 760mm).
So, to answer the OP, there is no fundamental difference between any of the expressions for pressure, other than some are more suited to a particular application than others. If your water district supplies 60psi at your meter, allowing for line losses and valves, bends, etc., you may have 50psi at the hose spigot, or about 115 feet of head pressure. If you needed to fill an elevated storage tank 120 feet above the centerline of the hose spigot, you would need a booster pump to get the water up to that level. In this context, Head, in Feet of Water, would be a more logical unit to use for pressure.