Thrust Block Req'd for Heat-Fused Connections?

7/15/2026

Have a question on whether or not thrust blocks are required for heat-fused connections.

Per Section 10.6.3 of NFPA 24, additional restraints are not required for heat-fused connections. Under PPI Chapter 7, for pressure piping systems that are joined by heat fusion, flanges are fully restrained and do not require external joint restraints or thrust blocks.

For the above case, is a pressure thrust block required?

We will use a concrete pad underneath the hydrant and PIV, but not a pressure thrust block.

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3 Comments

Glenn Berger

7/15/2026 09:28:55 am

If the system is completely restrained then thrust blocks are not required.

Jack G

7/15/2026 09:55:58 am

All mechanical connections such as hydrants , valves, bases, tees, risers, must be restrained using restraining flanges and or mechanical adapters because the HDPE piping is subject to movement from normal expansion and retraction. Utilize the products cut sheet and following installation instructions along with Nfpa product information is prudent.

Ryan Hinson

7/15/2026 09:56:12 am

Thrust blocks are but one of several given options for restraint of service mains per NFPA 24 (2025) Section 10.6.1. Butt-fusion is another per Section 10.6.2. See Section 10.6.3 where multiple means are addressed as well as .

Keep in mind that a restrained connection such as butt-fusion, rodding, or flanging only restrains the connection between and not any additional connections outside this. One must consider these other connections up- or downstream of the subject connection since internal pressures are trying to push all connection apart. If upstream pipe/fitting connections are not known to be individually restrained, thrust blocking 'bookending' both ends of each straight run of pipe should be considered.

Concrete blocking or flat stones installed beneath hydrants are required regardless of connection restraint as found in NFPA 24 Section 7.3.1*. See Figure A.7.3.1 showing these to be separate items. While they can be combined, they are governed by separate sections.

The intent is that all connections, whether by thrust blocking or other approved means, need to measures to prevent separation of each and every pipe/fitting/valve/pipe connection to achieve 'restraint against movement at changes in direction' where movement includes axial separation. See also Section A.10.6 and subsequent sections for additional indication of the intent.

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Thrust Block Req'd for Heat-Fused Connections?

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