Schedule 40 PVC Pipe Sizing Guide
Using this chart will tell you how many gallons to run inside of Schedule 40 pipe. Most people believe schedule 40 pipe is used for sprinklers, but its actually class 200. Class 200 PVC is the most common pipe type for irrigators. Schedule 40 pipe his a higher friction loss than Class 200 pipe. Meaning put more heads on a zone made by Class 200 than Schedule 40. Refer to the Maximum Safe Flow chart or the Friction Loss charts for more info.
Following this chart, if you wanted to run 75 GPM (Gallons Per Minute) through Schedule 40 pipe you’d look on the left and find that there. You’ll see that we must use 1 1/4” pipe for that many gallons.
But say our heads are using 3.0 GPM each. After we use that size pipe to plumb in 10 heads, we’re down to 45 GPM. Now we can reduce down to a 1” pipe size, and so on. This increases velocity as you move to the last head vs keeping the same size all the way down.