Quote:
Originally Posted by heirloomtomaguy
Just so you know by drilling a hole through a quarter you are not changing the pressure at all. By drilling the hole in a quarter you are regulating the flow of the water and once the water ceases flowing you will be right back at the pressure you started with. The drip tape i use requires no higher than 10-15 psi no matter whether it is delivered through a 1/8th inch hole or a 20 inch hole or pipe in my instance.
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Sure it does. Certainly you would agree that a valve decreases the pressure downstream? All the hole does is act like a valve which is 1. Not adjustable 2. Has an extremely low flow coefficient. A hole in a quarter is a miniature version of a submerged orifice plate which has applications all thru industry.
I am not claiming it is actually a regulator, its just that the pressure drop thru it goes up with the square of the velocity thru the hole, so if you make the hole small enough, (thereby increasing the velocity), the pressure drop increases by the square. So even if the upstream pressure were greater, not much more water will fit thru the hole, and the downstream pressure wont change much. This is approximately what you want for a dripper, and only a high end regulator will be able to do much better.