Hydrostatic Pressure (Fluid Mechanics - Lesson 3)

A description of hydrostatic pressure, along with the equation to calculate it, and an example.

[kingsleyukaulor]

This is very clever. Absolutely brilliant. Thanks for your help.

[StrongMed]

In most communities, the local water company has placed a large water tank either in a high tower or on top of a hill, and gravity provides the pressure to the individual homes (much like the example in the video). To change your home's water pressure, my first recommendation is to consult a professional plumber. If you're a do-it-yourself kind of person, then check out the YouTube video "Test and Adjust Your Home's Water Pressure" or search for "increase water pressure" on Wikihow.

[irdeena]

oh yes . i remember i learnt this last year . ugh . too bad i didnt pay any attention to my physic teacher when he explained it . btw, great video !!

[lh]

Very helpful, thank you for doing this video.

[StrongMed]

...also, to increase the water pressure in your home, if other steps don't solve the problem, you can install something called a "pressure booster". However, these are expensive, should only be installed by someone experienced with them, and local laws may require it to be inspected after instillation. Good luck!

[osteogenesiscongenita]

I've seen some of your videos and you have really good taste in music.

[StrongMed]

...The question as to whether one could power a home using just water pressure through your water main is an interesting one that I've never considered before. If you ran every faucet in your home 24/7, and using turbines, had the water continuously charge high capacity batteries that could provide transient increases in power when using something like a computer or TV, I suspect it's possible. But the water waste would be enormous, and it would not be remotely cost effective.

[StrongMed]

It probably uses gravity only - sort of. The water company may still require other means to get the water up into the high tank to begin with, unless the community's water source happens to naturally be at a high elevation (like you might see in the foothills of the Sierra Nevada. Every local water company is a little different based on geography, water source, number of customers, types of residences, etc...

[StrongMed]

In other words, using water to power your home would be like setting up a personal hydroelectric plant. However, the huge difference in scale, and use of clean potable water (which costs money), would make this not economical. (Although it would be an awesome science project...)

[dianaivanova]

Hi, could you explain to me why we took 54 meters into consideration and not only 4 meters? Because you're counting in your formula the hydrostatic pressure at the house to be the same as if the container with water was 54 meters high and directly vertically connected to the house.

I'm not sure if I'm clear enough but imagine this - you have 54 meters high container full of water, and then for sure the hydrostatic pressure at the bottom would be the whole distance from bottom to the top (atmosphere). In this case we could put 54 meters in the formula and it would be correct. If the house was connected by direct horizontal pipe to the bottom of the container, it's hydrostatic water pressure would equal the '54 meter high' weight of water.

But in this case where the house is connected by a thin pipe
(let's ignore it's inside volume of water since pipe would be very thin for better imagination, so also the weight of water solely in the pipe would be so small it can be ignored in the calculation of hydrostatic pressure)
to the bottom of a 4 meter high container of water, why the hydrostatic pressure in the pipe is not equal to the weight of the 4 meters of water? Why do you count also the distance of air (not density of water) between the container and the house, the 50 meters?

Because then the 54 meter high container full of water would cause exact same pressure on the house pipe than the 4 meter container which surely is not correct since there are many many more molecules and the mass of water and weight is much higher.

And second reason also is that if you count air distance from the bottom of container to the house just because this tiny tube connects them, it would mean that 4 meter high container of water would create 100x bigger difference in pressure on the house pipe when being on the house level versus when being on level 100 meters above the house. Which is non sense to my understanding. But I may be wrong so please explain. I cant get my brain through this.

[elrojoJazz]

Great lesson! Question on water pressure. Where does the water pressure come from in a common house or neighborhood. And is there a way to make my house have more or less water pressure? Does the water company supply the pressure?

[andrewty]

final answer for the question is 628, 937 Pa if anyone was wondering. ( 1 atm = 101, 325 Pa)

[elrojoJazz]

Actually I was thinking more on the lines of mini tesla turbines hooked right to your home water pipes, both hot and cold. Every time you take a shower. run the dishwasher, laundry or toilets. the mini turbines would generate power back to the electric grid. So no extra water would be wasted. How ever..you probably could not generate enough power to run your house on it. But still you would get paid to shower, clean laundry and go to the bathroom. haha :)

[nataliamatos]

I don't understand though, why is only the height relevant, when P=F/A??

[stxnw]

Why did you minus the water pressure of the house with the atmospheric pressure.

[elrojoJazz]

Hmm... So you are saying that every home in my area code.uses water pressure that is powered by gravity only?

Thats amazing! I thought the water company would need a pressure booster? or power waterturbine? If the pressure is all gravity. Thats free energy right?... could you power are home on water pressure?

[yashwanthsrk]

can you please explain, why you took 1000kg^3*9.8 at the house's pressure problem?

[michaelkingssa]

Hi what's the song in the intro??

[SuperKuku]

Great video but I have a question wouldnt the change in height be 54 - 50 =4 please

[mr_sher]

at 7mins in your video when you have your equation to calculate Phouse. I think you are wrong there, you have your minuses wrong...if you are saying Phouse - Patm (P2-P1) = pgdh...(dh = -54m ; Z2-Z1) so you either do it as Phouse = Patm - pg(54m) OR Phouse = Patm + pg(-54m).