It's a trick question, you can never get 4 bar of pressure with only a 20 m head.

The pressure due to a vertical column of liquid is equal to the density x height of the column x the acceleration due to gravity (little g = 9.8 m/s2).

Your height is 20m

Density of water is 1000 kg/m3

g = 9.8

So, pressure is 196,000 Pascals 

100,000 Pascal per bar, so you have 1.96 bar as the max pressure you could get, independent of flow rate or pipe size.  

Water Supply pressure
I recently read that it's a Segulah (others put it as a minhag) for a pregnant woman to bite off the Pitum of the esrog on Hoshana Rabbah for an easy labor.

(please correct me if I misunderstood it)

What is the connection between biting off the pitum and childbirth?



I read in the Halacha For Today email for Wednesday, 21 Tishrei 5772 (October 19, 2011). The original email read:


  It is a Segulah for pregnant women to bite off the Pitum of the Esrog on Hoshana Rabbah, and to give Tzedakah and daven for an easy labor. (See Likutei Maharich Sukkos page 106a. See also Elef Hamagen Siman 660:6 and Sefer Moed L'Kol Chai Siman 24:25 where a special Tefilah text is printed for the woman to say)

