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My overhead tank is at 12m height. From there a 50mm diameter pipe is running down and up to 50m horizontally and then raising from there to 6m to 3 bathrooms (no shower) and 3 wash basins. Is this height sufficient to supply water and how would I calculate the water pressure?

  • Hello, and welcome to Stack Exchange. What's the height difference from the tank to the wash basins? – Daniel Griscom Jun 9 '16 at 9:45
  • pipe diameter and pipe path have essentially no effect on pressure. Check out any intro to the physics of gravity. – Carl Witthoft Jun 9 '16 at 12:29
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    On the contrary - Pipe diameter (and length) has a significant influence with flow (not on static pressure) but 50mm pipe is likely large enough for it not to matter much. I have a gravity water system for a garden set up with 12.5mm pipe and that has a VERY large difference between static and flowing pressure as a result. Consult any reference on total dynamic head, or pipe friction. – Ecnerwal Jun 9 '16 at 14:36
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There are many online calculators for this, such as:

http://m.convert-me.com/en/convert/pressure/mwater.html

A meter of water is about 1.5 PSI so 12 meters is only 18 PSI and would be pretty disappointing for water pressure. You will have to run around in the shower to get wet.

When no water is flowing, the size of the pipe and the horizontal run are immaterial to this law of physics. It is the height of the water column that creates static pressure. When water is flowing, the pipe size and length may reduce the pressure, but in this case (assuming 50mm is an inside diameter) you shouldn't see any reduction in pressure.

Good luck!

  • Greater pipe size and lessened run won't increase the water pressure, but lessened pipe size and increased run may decrease the water pressure while a wash basin is in use. – Daniel Griscom Jun 9 '16 at 12:13
  • @DanielGriscom That is only true if there's a flow restriction somewhere. For all practical purposes (assuming the OP's 50 mm is ID) that won't happen here. – Carl Witthoft Jun 9 '16 at 12:30
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    Given it's going down 12m and up 6m, there is only half the amount of head - so slightly less than 9 PSI, or 0.589 Bar static pressure. No shower, so no running around in the shower needed. – Ecnerwal Jun 9 '16 at 14:31
  • Yeah I missed the "raising 6 m" hardly a trickle from this setup. – ArchonOSX Jun 9 '16 at 15:41
  • @Abdulaashiq KN And you need at least 30 psi (for a weak shower). Most houses have 40 - 80 psi. – Ben Welborn Jun 9 '16 at 17:34
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you have to just look the net height difference between the water level in the overhead tank and exit point of pipe. as per your data net height differnce is 7 mtrs( involving 1 mtr water level in overhead tank). you can calculate pressure using formula P= density of water* acceleration due to gravity g* net height difference h (we have not considered the atmospheric pressure as it is balanced at water level and exit) when you open the tap the calculated pressure is converted into velocity v=square root of(2*g*h). it means water comes out with calculated velocity accompanied with atmospheric pressure. velocity will not depends upon the number of openings but the net height difference.

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