Buried high-temperature steam and hot water piping systems with operating temperatures in the 250˚F to 450˚F range are often in service today with insulations that have significantly deteriorated or disappeared over time. Most systems operators are not aware of the level of degradation since the piping remains buried underground and is always out-of-sight out-of-mind.  Annular gaps between the conduit/outer casings and the carrier pipes and their residual insulation will often create major thermal deficiencies, as well as convective and vaporous conditions exhausting into the environment.  ConduFill® is a proven restorative technology and its unique performance as a high-temperature insulation can correct and serve the need to seal, reinsulate and enhance these thermally-inefficient piping systems without costly and infeasible excavations.

ConduFill® is injected while the system remains in service and is designed to withstand operating temperatures up to 400˚F (204˚C) on a continuous basis. As shown below, our 5-step restoration process prolongs the life of aged piping systems by injecting a rigid, high-temperature polyisocyanurate insulation into the annular space between the carrier pipe and the outer casing of the system:

1. Evaluate Piping System

Examine drawings and physically inspect the distribution system to determine its construction and if a void exists. If so, develop technical and field parameters by which the piping system will be accessed and restored.

2. Access Piping System

Small 18”-24” diameter vac digs at intermediate points above the line may be required to gain access the piping system. Small access points are opened up in the steel, concrete, terra cotta or HDPE outer casing to gain access to the void that is to be insulated. Manholes and vaults are also instrumental in providing additional access points.

3. Strategize Application

Teflon® tubing is inserted into the void space either at vac dig access points or manhole access points. Planning, strategies and measurements of tubing within the system ensure complete coverage when ConduFill® is pumped into the target void.

4. Inject ConduFill®

The rigid insulation is injected into the target void in between the carrier pipe and the outer casing, expanding 30 times its own volume. A Mobile Pumping Unit (MPU) equipped with pumps, metering equipment, generators, heaters, chillers and holding tanks will establish critical temperatures and pressures before dispensing the polyisocyanurate formulation into the piping system.

5. Restore Surfaces 

Any necessary vac digs will be backfilled and street, sidewalk, grass and other surfaces will be restored to specification.


Technical Data

service_temp_condufill_tst – Copy
  • Service Temperature
  • 400°F
  • K-factor
  • .18 btu-in/hr-ft2-°f
  • Closed-cell Content
  • 95%+
  • Compressive Strength
  • 16 – 17.5 psi
  • Density
  • 3.0 pcf
  • Water Absorption
  • Less than 2%


The minute ConduFill® is injected into a buried piping system, energy savings and reduced fuel costs begin. Restoration usually results in a 40-90% heat loss reduction and an ROI of 2-5 years depending upon on energy costs.

Nearby utilities such as fiber optic, electrical and water lines can become damaged by the heat of nearby distribution lines. ConduFill® will eliminate this conflict and protect from further damage.

Accessing the piping system through small vacuum digs and manholes minimizes disruption of vehicular and pedestrian traffic.

ConduFill® will upgrade and repair the insulation thereby extending the life of the distribution system.

The formulation expands 30 times its own volume to effectively fill the target void and to seal off breaches, cracks and holes that have developed in the outer casing over time.

Unsightly vapor is usually a sign of poorly insulated distribution piping. The vapor is eliminated as water can no longer get into the system due to the presence of ConduFill®.

There is no need for shutdowns or outages. The piping system can remain in service throughout the entire restoration process.

The cost of excavating and replacing buried distribution piping ranges from $400 to $2000 per LF. ConduFill® is usually 20-40% of the cost of complete replacement.

Common Types of Buried Piping Systems

  • Box-pour Concrete
Trenchconduit – Copy
  • Trench
  • Drainable-Dryable (Class A)
  • Round Top Concrete
dualpipeconduit – Copy
  • HT Hot Water

HTHW Pipe Insulation Upgrades at Rutgers University

TST successfully completed a thermal restoration project at Rutgers University, Camden Campus with its innovative ConduFill® technology.  A section of buried 12″ dual HTHW piping was thermally restored after 294 LF of ConduFill® was injected into the void space within a 20-inch diameter outer steel casing. The presence of ConduFill® allows the university to restore thermal efficiency, prolong the life of the piping system and avoid immediate and costly replacement.  TST has successfully completed dozens of repairs on multiple campuses at Rutgers University since 2002.

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