Pipe sizing is one of the factors in calculating your gallons per minute. I recommend 1" class 200 PVC pipe in most circumstances. You may need 1¼" for your main line on larger jobs and when pressure is an issue. I don’t recommend ¾" pipe for do-it-yourself jobs because the cons outweigh the pros. Cons: It adds the complication of another size of fittings and pipe you need on hand. Pros: A negligible cost savings. Note: ¾" pipe offers no advantage in regards to water pressure.
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