Plumbing – Water Pressure question and pipe sizing

plumbingwater-pressure

I recently ran some 3/4id poly pipe from my house about 300ft down a slight hill to my shop and garden area. I was not able to tie directly in to the underground pipe in the yard because my pressure regulator is under my house and I do not have a good way to get pipe out of the house underground. my solution was the put an irrigation valve box near a wall spigot and run a short, heavy duty hose from the wall to the valve box to feed the pipe. the inside pvc feeding the spigot I used is 1/2in. My issue with my flow at the garden is my flow, not the pressure. when I let pressure off and timed filling a 5 gallon bucket I calculated my volume to 4.2 gallons per minute, and my drip irrigation system will draw about 5.3 gallons per minute. My main question is trying to locate the bottleneck. its it mostly likely to be the 1/2 pvc pipe in the house? if so I can run a dedicated 3/4 line from closer to the house incoming line to the spigot, or would that cause the spigot to be a bottleneck? any help here would be greatly appreciated.

Best Answer

300 feet of 3/4 poly is, itself, a restriction. That's a very long run for pipe that small.

Adding a section of 1/2 PVC doesn't help, but unless it's quite a long section, the 300 feet of 3/4 dominates the total dynamic head (which is what limits your flow.)

Is your incoming pressure so high that it would burst the pipe? If not, skipping the path through the PRV and house might be the easiest solution, as there would be more pressure head to start with, and you can put a garden hose or irrigation pressure reducer (quite inexpensive) at the end of the line, if needed.

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