The U.S. Consumer Product Safety Commission’s far-reaching drain-cover recall is the largest in industry history.

The action “[affects] hundreds of thousands of pools,” said Scott Wolfson, CPSC’s public affairs director. The agency classified the recall as voluntary because manufacturers are cooperating. But Wolfson sought to clear up any confusion: “Voluntary does not mean optional.”

Misunderstandings regarding which pools are affected apparently led some cities to close all pools over the busy Memorial Day weekend. For example, Jacksonville, Fla., delayed opening pools during the holiday, citing concerns about the recall. Many pools were later opened.

The recall has received nationwide media attention and prompted one state attorney general to issue a warning to consumers.

“I strongly encourage parents to call their local pool operators to ask two very important questions — if the pool contains one of these dangerous drains, and whether the facility complies with safety standards,” said Illinois State Attorney General Lisa Madigan in a public statement.

Replacements or retrofits are mandatory on shallow-water vessels, which include wading pools, kiddie pools and spas. Single-drain pools also must be addressed, unless  they have unblockable drains, gravity feed systems or drain covers installed before Dec. 19, 2008. CPSC is advising that those facilities be closed until retrofits or replacements can be made.

Pools deeper than 24 inches with multiple-drain systems do not need to be addressed.

However, some locations are enforcing the recall farther than its intended scope. An official with the Texas Department of State Health Services announced that all recalled drain covers statewide are to be replaced, even those installed in dual-drain pools.

Texas law mandates that every commercial pool must comply with the Virginia Graeme Baker Act, which requires all drain covers to meet the standard ASME/ANSI A112.19.8. Because the recalled products don’t meet that standard, they aren’t allowed in Texas, said Kathleen O. Moore, an official at the Texas Department of State Health Services, in a note sent out to affected parties.

She is allowing pools to be prioritized based on risk level, so that some pools may be addressed sooner, others later.

Connecticut’s Health Department also sent out a memo directing its municipal pool operators to observe the recall, but not outlining enforcement or deadlines.

While the action involves 1 million drain covers, the recall’s reach is being characterized quite differently, depending on the source. CPSC officials stated that hundreds of thousands of pools are affected, but the Association of Pool & Spa Professionals contended on its Website that the recall will affect “well below 100,000 [pools].”

APSP is acting as a spokesperson for seven of the eight manufacturers involved in the full-scale recall.

The companies working with the organization declined to comment for this story.

The recall includes models by the following: A&A Manufacturing, AquaStar Pool Products, Color Match Pool Fittings, Custom Molded Products, Hayward Pool Products, Pentair Water Pool and Spa, Rising Dragon Plastics, and Waterway Plastics.

Two other manufacturers had affected products, but were not included in CPSC’s public announcement. Lawson Aquatics and Paramount Pool & Spa Systems each had fewer than 100 of their recalled units in circulation and had the capability to make direct contact with customers to arrange for appropriate action.

Depending on the model, recalls could involve replacement — of just the cover or the entire drain assembly — or repair, which could be as simple as snapping a new piece onto an existing drain cover, as with Waterway Plastics’ retrofit.

CPSC said most manufacturers will pay for parts and labor, but each producer has its own process, usually involving several steps.

Additionally, APSP said that all professionals, whether installers performing the repairs or manufacturers providing the product, should keep records of every drain cover replaced, along with the pool or spa type, flow rating and model of the existing drain cover. The CPSC will be monitoring the recall and could ask for records at any time, the group said.

Kendra Kozen contributed reporting for this article.