When I open a plumbed tap (faucet)slightly, water comes out and then pressure drops.
I don't mind this but cannot think why it is the case as water is (relatively) incompressible.
I think I noticed it too in the past, but only in one or two faucets.
I'm not sure why it happens (or why it doesn't happen in some faucets only) but I think it could be a result of pressure from the sides of the faucet. When the water is stationary the pressure from the sides of the facuet on the water is high, and when the water start flowing the pressure decreases. When the water get to their maximnum speed, the pressure stablizes.
I could be totally wrong, though.
Thanks for the reply.
I thought about that. That would assume the sides of the tap were elastic as opposed to rigid. I don't think it's that.
I think it's something to do with gas compressed in a closed system driving fluid thorough when pressure is released but I don't know quite why the gas does not just escape instead.
The waterpressure builds up in the pipe before you open the faucet, when the water is released to flow to a point of less pressure the pressure drops to a lower point and is sustained at that point consistent to the pressure applied to the water from the pumping source(well or munincipal pump).
This would imply that the water pressure in the system is sufficient to compress the water, hence build up pressure via the exertion of a force related to elastic properties of the water - which I'm incredulous as water is almost incompressible at low pressures. I agree with your analysis but I still do not know how that pressure is built up - the only explanation I can think of is dissolved gasses giving the elasticity - what do you think?
The pressure applied to the water comes from a pump, you can place water in a pipe but unless you have some sort of pressure applied the water only flows to a lower point of gravity. It is the same with a balloon, as long as you blow into the balloon the balloon expands to accomodate the air pressure until the rubber reaches the breaking point then it bursts. You can also burst a water pipe if the pumping force is greater than the materials tensile strength, it happened in my washing machine hose the water pressure at my home is greater than the other homes going uphill so now I have to turn those hoses off until I use them. There has been several homes in my neighborhood on the downhill side that have had the bottom of their water meter explode because of the materials failure to hold all that pressure(from the waterpump and gravity applied to that because of downhill grade). Maybe this would be a good experiment for mythbusters to try at least it would be tamer than some others I have seen them do.
Got an answer for JGerroll? Would you like to comment on the posted answers, or vote for the one which you think is the best?
Sign up for a free account, or sign in (if you're already a member).
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them
