Pipe & Gasket Design: Separate Components or a System?

The new ASTM C1628 standard enhances how projects specify pipe and gasket design.

By Mike Miller

Precasters that make joints with rubber gaskets are familiar with ASTM C443, “Standard Specification for Joints for Concrete Pipe and Manholes, Using Rubber.” Companies brought their equipment and manufacturing processes into conformance with this standard, making sure the proper joint design, gasket design and source, inspection protocols and test data fully supported the products.

However, a recent addition to ASTM standards for pipe and gasket design means precasters who use pipe gaskets in their products need to be aware of coming changes. The new ASTM C1628, “Standard Specification for Joints for Concrete Gravity Flow Sewer Pipe, Using Rubber Gaskets,” shows a mix of ASTM C443 and ASTM C361, with a little industry certification added. While the standard has been around for several years, it is now reaching the point where it may appear as a project specification requirement, and precasters need to be ready.

ASTM C1628 varies from ASTM C443, which may require additional design analysis and modifications to equipment, staff and processes for many precasters. The new standard introduces a different way of thinking about joint and gasket design.

The old understanding is pipe and gaskets are related but separate components. Joint designs have been a compromise between ease of manufacturing and product precision. The new thinking is the pipe joint and gasket form a system and minimize variation by providing sufficient inspection efforts at the proper process points to reduce or eliminate problems. As a result, a higher level of overall quality is achieved and everyone benefits. Overall, costs could be reduced for both the precaster and the customer.

ASTM C1628 introduces new thinking about joint and gasket design. (Photo courtesy of Press Seal Gasket Corp.)

A table available here compares the significant differences between the two standards, revealing there are changes to requirements in almost every area. Some precasters will discover many products and processes are compliant or can easily be made compliant, while others will discover compliance challenges. Legacy equipment may need to be replaced, inspection gauges and processes may need improvements, gaskets may need to be changed or a new supplier may need to be found. Additionally, staff may require extra training.

While the changes are numerous, some of the key differences for precasters and suppliers to know include:

• Scope. This is what defines which products are included within the standard. ASTM C1628 provides further pipe application guidance to projects “where measurable or defined infiltration is a factor of the design.” ASTM C1628 is not intended to supplant ASTM C443 as an appropriate gasketed joint system for vertically placed manhole structures.
• Gasket physical properties. Both standards require gaskets as specified under ASTM C1619. However, the classes are different and the requirements for ASTM C1628 are considerably more stringent. The requirement in ASTM C1619 that all tests be conducted on actual product samples will catch suppliers who avoided the transition when ASTM C443 was changed.
• Gasket dimensional tolerances. Design tolerances for gaskets in ASTM C1628 are about half what they are in ASTM C443, meaning supplier changes will have to be made.
• Joint design. An important change in ASTM C1628 is it limits joint tapers to no more than 2 degrees, 3 degrees if testing proves adequate. ASTM C443 allowed taper angles up to 3.5 degrees, 5 degrees if tested. Precasters with equipment having a taper in excess of 3 degrees will need to re-equip to meet the new standard. Additionally, ASTM C1628 includes detailed requirements for joint design.
• Test methods (gaskets). ASTM C1628 requires the precaster to sample gaskets and perform several quality checks.
• Performance requirements. ASTM C443 and ASTM C1628 both require hydrostatic tests in the straight homed position and in the deflected position. However, ASTM C1628 specifies both tests to have an off-centering shear load applied. ASTM C1628 also requires a structural shear test. As a convenience to the testing producer, there is an option to conduct all the C1628 hydrostatic and structural testing as a single test to the worst case condition.
• ASTM C1628 requires that the bell and spigot of every pipe be measured. Whether this means every size, every type or every individual stick of pipe is open to interpretation.
• Appendix. ASTM C1628 provides a suggested checklist to assist owners and designers responsible for reviewing joint design and geometry submittals.This checklist shows a Joint Data Form that includes important details needed for a complete joint submittal analysis.

Like any standard, the road to acceptance and implementation of ASTM C1628 may take years. These changes represent a push for improvement in the performance of products that comply and will likely face some setbacks. If implemented, companies that are compliant with ASTM C1628, will also be compliant with ASTM C443. This is crucial if ASTM C443 is important in your market area.

Mike Miller is owner of Large Caliber Design, LLC, and remains active in sealing product design and development, as well as standards work with ASTM.