“Bitumastic” gets used on job sites the way “Sawzall” gets used for any reciprocating saw. People say it to mean any thick black coating: coal tar, asphalt, bituminous mastic. You’ll also see it spelled “bitomastic.” The product name belongs to Carboline, and the two Bitumastic products most people have in mind — Bitumastic 50 and Bitumastic 300M — are both coal tar based.
That matters the moment someone asks to coat the inside of a water line with it. The short answer: coal tar Bitumastic does not go on the interior of drinking water pipe. Here’s why, and what goes there instead.
Why Coal Tar Is Out of Potable Water Service
Coal tar coatings protected buried and submerged steel for more than a hundred years. They were cheap, thick, and water didn’t get through them. For a long stretch they were also used inside water pipe. The first edition of the American Water Works Association standard for steel water pipe linings, AWWA C210-78, was titled Coal-Tar Epoxy Coating Systems for the Interior and Exterior of Steel Water Pipelines.
That changed. Coal tar and coal tar pitch are classified as known human carcinogens, linked to skin, lung, bladder, and other cancers. Later editions of AWWA C210 dropped coal tar entirely. The current standard, AWWA C210-24, is Liquid-Epoxy Coatings and Linings for Steel Water Pipe and Fittings — two-part, chemically cured epoxies with no coal tar in them.
If a spec, a drawing, or an old habit calls for coal tar epoxy on the interior of a potable line, that spec is decades out of date.
What NSF/ANSI/CAN 61 Actually Requires
NSF/ANSI/CAN 61 is the standard that governs every material that touches drinking water: pipe, fittings, valves, gaskets, tank linings, and the coatings on all of them. Most state drinking water programs require it for public water systems.
A product certified to NSF 61 has been tested to show it doesn’t leach contaminants into the water above health-based limits. The health effects criteria themselves now live in a companion standard, NSF/ANSI/CAN 600. When you see “NSF 61 / NSF 600 compliant” on a product data sheet, that’s the certification you need.
A few things contractors and owners get wrong about NSF 61:
- Certification is product-specific. A manufacturer having one NSF 61 product doesn’t make their whole line approved. Check the exact product on the NSF certified products listing.
- Certification has conditions. Listings specify a maximum film thickness, minimum pipe diameter or tank size, number of coats, and cure schedule. Apply it outside those limits and it’s not an NSF 61 installation anymore.
- Cure is part of compliance. An NSF 61 epoxy that hasn’t fully cured before the line is flushed and put in service can leach solvents and uncured resin. The cure time and temperature on the listing are requirements, not suggestions.
What Goes on the Inside of Potable Water Pipe
For steel water pipe, the common NSF 61 interior options are:
Liquid epoxy linings (AWWA C210). Two-part epoxies applied by spray at the plant or in the field. This is what replaced coal tar epoxy. Coatings manufacturers like Carboline, Tnemec, and PPG all publish NSF 61 lining systems.
Fusion-bonded epoxy (AWWA C213). A powder epoxy baked onto the pipe at the factory. Tough and consistent, but it has to be done in a shop.
Cement mortar lining (AWWA C205). Still widely used on large-diameter steel and ductile iron water main.
NSF 61 asphalt coatings. Not every bituminous coating is coal tar. Some asphalt-based pipe coatings carry NSF 61 and NSF 372 certification, like the asphalt pipe coatings from Eaton Chemical. These are asphalt, not coal tar. Don’t assume a black coating is either one — read the data sheet.
Where Bitumastic Is Still the Right Call
None of this makes coal tar Bitumastic useless. It’s still one of the most forgiving, cost-effective barrier coatings for steel and concrete that’s buried or underwater and never touches drinking water:
- The exterior of buried steel pipe (Bitumastic 300M’s data sheet references AWWA C210 for exterior use)
- Sanitary sewer and storm pipe, manholes, and wet wells
- Non-potable process water and wastewater lines
- Steel piling, foundations, and below-grade structural steel
- Submerged steel on seawalls and water control structures
What these all have in common: no drinking water contact and no sunlight. Coal tar breaks down under UV, so Bitumastic is a below-grade and immersion product only. We cover those uses in detail in Bitumastic on New Non-Potable and Buried Pipe.
The Surface Prep Doesn’t Change
Whether it’s an NSF 61 epoxy on the inside of a water line or coal tar epoxy on the outside of a sewer force main, the coating is only as good as the steel under it. Both call for abrasive blasting — typically SSPC-SP 10 near-white or SSPC-SP 5 white metal for immersion service, with a sharp angular profile in the range the product data sheet specifies.
For potable water work there’s one more concern: what’s left behind. Spent abrasive, dust, and salts left on the surface get trapped under the lining. Inside a water pipe, that means a coating failure and a contamination problem. Blasting for potable service has to finish with a thorough blow-down and vacuum, and soluble salt testing if the pipe has been sitting in storage or near road salt.
What to Tell Your Engineer or Coating Supplier
If you’re specifying or bidding a new pipe job with both potable and non-potable lines, get these answers in writing before anybody orders material:
- Which lines carry drinking water, and which don’t?
- What NSF 61 certified product is specified for potable interiors, and what are its listing limits (DFT, diameter, cure)?
- Is coal tar epoxy or Bitumastic being used anywhere, and is every one of those locations non-potable and below grade or submerged?
- What SSPC surface prep grade and anchor profile does each product call for?
- Who is doing holiday testing on immersion linings before the pipe goes into service?
Getting the product wrong on a potable line isn’t a touch-up. It’s a tear-out.
Blasting Jack provides abrasive blasting and surface preparation for new and existing pipe, tanks, and water infrastructure throughout Michigan, blasting to the SSPC grade and profile your coating spec calls for. Contact us to talk through the prep on your next pipe coating project.