Understanding Pipe Sizes: Nominal vs. Actual Measurements.
Pool and hot tub plumbing uses nominal pipe sizes, meaning the listed size (like 1.5" or 2") refers to the inside standard trade size - not the actual physical measurement. A 1.5-inch PVC pipe actually measures approximately 1.9 inches on the outside, while a 2-inch pipe measures about 2.375 inches. To make sure you order the right fittings for your spa repair, always measure the inside diameter of your existing pipe before buying. Click the button below for detailed sizing guide.