NSF 61: What It Certifies and What It Does Not

Wally Bates

Sep 26

2 min read

Every potable water tank specification says the interior lining must be "NSF 61 certified." Most people read that as "safe for drinking water." That is correct, but it is only part of the picture.

What NSF 61 tests

NSF/ANSI/CAN 61 is a health-effects standard. The certified coating is applied and cured according to the manufacturer's instructions, exposed to water under controlled conditions, and the water is analyzed for anything that leaches out: solvents, metals, unreacted resin.

The listing is specific. It names the product, the maximum thickness, and the cure schedule, and sometimes a minimum tank size. A thick lining in a small tank means more coating per gallon of water, so size matters.

What it does not test

NSF 61 says nothing about whether the coating will perform. It does not test adhesion, abrasion resistance or service life. Performance is covered by AWWA D102 and by the manufacturer's track record.

A recent change worth knowing

In 2023, limits for xylene, ethylbenzene and toluene were lowered substantially, and the health criteria now sit in NSF/ANSI/CAN 600. That change ended certification for most solvent-based potable coatings. Tnemec Technical Bulletin 20-113 R1 covers the details.

Where projects go wrong

The cure schedule. A lining certified with a 7-day cure at 75°F that is filled after 3 days in a cold tank may not meet its listing, and the water may taste like it. Utilities test for taste and odor, and a failed test means draining the tank.

What to check in your spec

Require the current NSF/ANSI/CAN 61 listing for the exact product, not the product family.
Confirm the listed maximum thickness and any minimum tank size.
Write the listed cure time and temperature into the return-to-service requirements.
Plan for heat or dehumidification if the work falls in cold weather.

Further reading: Tnemec Regulatory Matters 97-03 R2 and Technical Bulletin 20-113 R1. Standards: NSF/ANSI/CAN 61, NSF/ANSI/CAN 600, AWWA D102.

Talk to a consultant. Atlantic Coating Consultants helps owners, engineers and contractors in PA, NJ, DE, MD, DC, WV and OH with specification writing, on-site condition assessment, training, product recommendations and field support. Call 484-644-5303 or email atlantic@tnemec.com.