The committee in charge of the ANSI/APSP-7 Standard for Suction Entrapment is removing language regarding line velocities from the main text.
The standard addresses how pools and spas should be built to prevent entrapment and has long stipulated that water velocities at the drain should be kept to 6 feet per second or less. The faster water moves, the more vacuum it creates, so the goal is to keep the water at safe speeds.
The standard may still advise velocities of 6 fps or less. However, instead of appearing in the main body, where it would have to be followed, the language may run in the appendices, which contain informative language rather than absolutely requirements.
The organization continues to encourage lower velocities, said Steve Barnes, APSP’s Technical Committee chairman. The 6-feet-per-second rule will remain in other standards, such as the APSP-5 American Standard for Residential Inground Swimming Pools and ANSI/APSP/ICC-15 American National Standard for Residential Swimming Pool and Spa Energy Efficiency.
More importantly, the issue of velocity is being addressed in the rewrite of the drain cover standard APSP-16 Standard Suction Fittings for Use in Swimming Pools, Wading Pools, Spas and Hot Tubs.
The velocity limits were written into ANSI/APSP-7 as a way to make up for certain vulnerabilities seen in drain covers when the standard was last updated, in 2006. Now that all drain covers must undergo certain tests, and flat models are prohibited, the 6-feet-per-second rule is no longer necessary, writers of the standard believe.
“There’s no question that velocities affect safety,” said Paul Pennington, head of the Pool Safety Council, a Washington, D.C.–based group of safety products manufacturers and safety advocates. “But the question is exactly how and where to apply [the velocity stipulations]. Since it is part of the suction outlet system, it probably does belong in the APSP-16 standard.”
While some still worry about higher velocities occurring if a drain cover is removed, APSP committee members think the drain cover standard will address this concern.
The change also is related to enforcement of the standard. While a new system can be engineered to generate certain velocities, it is impossible to verify velocities in existing systems accurately enough to satisfy some government officials, Barnes said. There’s no device to determine velocity, and some officials don’t accept mere calculations.
“If it were easy to enforce, like with a flow meter or by measuring pipe ... then we wouldn’t change it,” Barnes said. “The problem is when they inspect to something that can’t be verified.
“But the only reason we can take it out is because the safety function that it provided ... has been addressed by the new drain covers.”
ANSI/APSP-7 will soon enter the review and comment stage, Barnes said.