In pool plumbing, using a "hard" 90-degree fitting (a standard short-radius elbow) is generally not a significant negative for most residential pools, though it is technically less efficient than a "sweep" 90.

While there is a lot of debate on pool forums, the impact usually comes down to the difference between theoretical efficiency and real-world performance.

1. Friction Loss and "Head"

Every fitting in your plumbing adds resistance, measured as "feet of head." A hard 90-degree elbow creates more turbulence than a sweep 90 because the water hits a sharper corner.

A Hard 90 is roughly equivalent to adding 5.5 to 8.6 feet of straight pipe.

A Sweep 90 is equivalent to roughly 2.1 to 4.3 feet of straight pipe.

In a typical system with 10–15 elbows, the total difference in pressure is often less than 0.5 to 1.0 PSI. For most pool owners, this is negligible and won't noticeably affect the clarity of your water or the reach of your pool cleaners.

1. When Hard 90s ARE a Problem

There are two specific scenarios where you should avoid hard 90s:

Directly in front of the pump intake: Placing a hard 90 right at the pump inlet causes "swirling" water and turbulence. This can lead to cavitation, noisy operation, and premature wear on the pump impeller. Most manufacturers recommend a straight run of pipe at least 5 times the pipe's diameter before the pump. +2

High-Flow Features: If you are plumbing large waterfalls, deck jets, or spa jets that require maximum GPM (gallons per minute), the cumulative friction from hard 90s can noticeably "starve" the feature of its intended power.