# RCP Stormwater Joints: Evidence Needed for Internal Sealing

Canonical: https://reliancetrenchless.com/en-GB/blog/rcp-stormwater-joint-sealing-review

Published: 2026-10-25 · Updated: 2026-10-25 · By Reliance Trenchless

What to document before an internal seal review for an RCP stormwater joint: joint type, leakage path, geometry, service conditions and seal configuration.

An RCP stormwater joint that keeps leaking is rarely solved by a single photograph of water entering the pipe. Before an internal seal can be reviewed, the project needs a small evidence package: the joint type, the path the water takes, the measured geometry on both sides of the joint, the stormwater and groundwater conditions, and the proposed seal configuration in writing.

The [Reliance internal pipe joint seal](https://reliancetrenchless.com/en-GB/products/internal-pipe-seal) is a mechanical assembly that spans a joint from inside the pipe. It is not a crack injection, a structural lining or a replacement for missing concrete. Its review depends on facts that only the project can supply, which is why the first step is to separate what is known from what is still an assumption.

## What evidence does an RCP stormwater joint review need?

The American Concrete Pipe Association's design manual describes pipe joints as components selected for several jobs at once: resisting infiltration and exfiltration, controlling leakage under internal or external head, accommodating movement, resisting shear and maintaining hydraulic continuity. The same chapter notes that field performance depends on the joint itself, the severity of service and the care taken during installation ([ACPA design manual, 2014](https://resources.concretepipe.org/hubfs/Resources/ACPA/Design/ACPA-Design-Manual-2014-Version.pdf), Chapter 5, pp. 93–96).

That is the right frame for a stormwater review. An RCP joint is not automatically a rubber-gasketed joint, and a rubber-gasketed joint is not automatically the same detail from one project to the next. The evidence package has to identify the actual joint, not just the pipe material.

## 1. Identify the joint type before assuming a seal will fit

ACPA describes several concrete pipe joint families. Mortar- or mastic-packed bell-and-spigot and tongue-and-groove joints have no inherent watertightness and depend on workmanship; movement after installation can crack the packing. Compression rubber gaskets, O-ring gaskets and steel end-ring joints are different starting points, and the manual links the rubber-gasket family to [ASTM C443](https://doi.org/10.1520/C0443-21), the specification for joints for concrete pipe and manholes using rubber gaskets (ACPA, pp. 93–95).

For the review, send the construction specification, the as-built or record drawing, the pipe class and the joint detail. If the record only says "RCP" or "rubber gasket", say that. Do not infer the joint profile from the pipe diameter. Where the drawing and the field observation disagree, send both and identify which one is being treated as the current condition.

## 2. Separate joint leakage from adjacent pipe damage

Water appearing near a joint can come from the joint opening, a crack in the barrel, a failed previous repair, a service connection or a defect at a manhole. These are different review paths. An internal joint seal is intended to address leakage across the joint; it does not restore a cracked or displaced concrete barrel.

Use the inspection record to locate the observation in the line: chainage or manhole-to-manhole distance, clock position, direction of flow and the camera's direction of travel. A still image without that context is weak evidence because the same dark line can be a joint, a crack or a shadow. If CCTV is available, send the video reference and the time range, not only a cropped frame. If it is not available, state that the location is unverified and provide whatever drawings, photographs or maintenance records exist.

![Conceptual cross-section of a reinforced concrete pipe joint with numbered callouts for joint type, joint opening, offset, adjacent crack and available sealing surface.](https://reliancetrenchless.com/assets/img/Blog/rcp-stormwater-joint-sealing-review/rcp-joint-evidence-map.svg)

**What to locate in an RCP joint record.** 1: joint type and gasket zone; 2: joint opening at the crown; 3: offset or step at the invert; 4: a separate crack or wall defect; 5 and 6: the surface available on each side of the joint. Conceptual diagram, not to scale. It does not establish an allowable joint opening, a minimum seating length or a seal size.

## 3. Record the geometry the seal must cross

The useful dimensions are the ones that describe the actual opening, not only the nominal pipe size. Record the internal bore on each side of the joint, the joint opening at several clock positions, any visible offset or step between the two bores, and the condition of the surface on each side where a seal would sit. Note obstructions, lining changes, deposits and nearby connections.

ACPA makes an important point about joint opening: the maximum permissible opening varies with the joint configuration and is best obtained from the pipe manufacturer (ACPA, p. 99). A generic table or a value copied from another project is not a substitute for the project's joint detail. The same logic applies to the available sealing surface. The total width of a rubber component is not the usable contact area, and a nominal diameter is not a measured bore. The [internal joint seal measurement guide](https://reliancetrenchless.com/en-GB/resources/internal-pipe-joint-seals-measurement-guide) sets out these fields separately and explains why they should not be collapsed into one number.

The Reliance brochure lists rubber widths of 270 mm, 350 mm and 500 mm, and describes slot-type and screw-type stainless steel sleeve arrangements. Those are catalogue options, not a statement that any one width suits a particular joint. The brochure also gives a size range of DN200–DN3000, while a public Reliance video describes DN150–DN4000. This article does not resolve that difference; ask for the applicable range and configuration in the quotation, and keep the source of each figure in the record.

## 4. Describe stormwater and groundwater conditions

Record whether the line is normally dry, part-full or surcharged, and whether the joint is exposed to external groundwater, sediment, grit or repeated wetting. Those conditions belong in the review because they affect the service environment and the acceptance test, not because they can be converted into a seal rating without product-specific data.

Provide the design flow or head, the maximum observed groundwater level relative to the pipe invert, the duration and frequency of surcharge, the conveyed medium, temperature and any known debris or sediment load. Keep the units, date and source with each value. If a number is a design assumption rather than a measurement, label it that way.

ACPA notes that specifications should define allowable infiltration or exfiltration rates and acceptable joint types after groundwater conditions are evaluated (p. 96). It also lists ASTM C969 for infiltration and exfiltration acceptance testing and ASTM C1103 for joint acceptance testing (pp. 89–90). If the project cites either method, send the actual test section, acceptance criteria and the edition named in the contract. An internal seal review is not a substitute for the project's acceptance test.

Material compatibility is a separate question. The brochure lists AISI 304, 316L and a designation printed as "318L (2205)". That printed designation should not be silently treated as a standard grade equivalence. Ask for the proposed material certificate and a written clarification of the grade. A generic statement that the rubber is "suitable for water" does not establish compatibility with a specific stormwater or groundwater chemistry.

## 5. Check the proposed seal against the actual joint

The product review should end with a configuration, not just a model name. Ask for the proposed sleeve material, rubber width, ring type, installation tools, access route and the dimensions that the supplier has checked against the submitted records. The brochure illustrates installation tools and ring arrangements, but the proposed assembly still has to be matched to the actual pipe and access.

Access is part of the evidence. Record the entry opening, the route to the joint, the space available for the assembly and tools, and any confined-space or traffic-control constraints that affect how the work can be done. Do not treat a product photograph as proof that the assembly will pass through a particular opening.

![Conceptual diagram of four parallel evidence sets: joint identity, inspection record, dimensional sketch, and service and acceptance documents.](https://reliancetrenchless.com/assets/img/Blog/rcp-stormwater-joint-sealing-review/rcp-evidence-package.svg)

**Four records, not a sequence.** 1: pipe and joint identity from the specification or record drawing; 2: inspection evidence with location and direction; 3: a dimensioned sketch of the actual joint geometry; 4: service conditions and project acceptance documents. The sets are reviewed together; one does not replace another.

## What to send for an internal seal review

| Record | What to include | What it does not prove |
| --- | --- | --- |
| Joint identity | Specification, record drawing, pipe class and joint detail | That the installed joint matches the drawing |
| Leakage observation | Inspection reference, location, clock position, flow direction and images | That the joint is the only source of water |
| Geometry | Actual bore on each side, joint opening, offset, available surface and obstructions | That a catalogue model is approved for the condition |
| Service conditions | Medium, head, groundwater level, temperature, sediment and units/sources | Material compatibility or a pressure rating |
| Project acceptance | Test method, edition, acceptance criteria and required submittals | That the installed seal will pass the test |
| Access | Entry opening, route, tool space and site constraints | Permission or a safe procedure to enter |

A complete enquiry can be short. State the joint location and the leakage task, attach the records that exist, mark missing values as unknown, and ask for the additional information needed to review the seal, material configuration and installation equipment. The [internal joint seal product page](https://reliancetrenchless.com/en-GB/products/internal-pipe-seal) and the [measurement guide](https://reliancetrenchless.com/en-GB/resources/internal-pipe-joint-seals-measurement-guide) provide the starting fields; the project records decide whether the review can move forward.

## FAQ: RCP stormwater joint sealing

### Can an internal joint seal repair a cracked RCP barrel?

No. An internal joint seal is intended to span and seal the joint. A crack, broken bell, displaced section or loss of concrete is a separate condition that needs its own assessment. Send those observations with the joint records so the reviewer can decide whether the joint seal is still the right scope.

### What is the most important dimension for an RCP joint seal review?

There is no single dimension. The actual bore on each side, the joint opening, any offset and the available surface all affect the review. The nominal pipe size identifies the line, but it does not replace a measured bore or a joint detail.

### Is DN150–DN4000 the confirmed size range for the Reliance internal joint seal?

Do not treat it as confirmed from this article. The Reliance brochure gives DN200–DN3000, while a public Reliance video describes DN150–DN4000. Ask for the applicable range and the exact configuration in the quotation, and keep the source of the figure with the project record.

### Do I need a CCTV survey before requesting a review?

A CCTV record helps locate the joint and separate it from cracks, connections and other defects, but it does not replace dimensional measurements. If no survey is available, say so and send the drawings, photographs and maintenance records that do exist. The review can identify what is still missing; it should not pretend the location is confirmed.

For a joint-specific review, send the records through the [internal joint seal enquiry entry](https://reliancetrenchless.com/en-GB/contact#product=InternalPipeSeal). The form opens the available submission method; it does not confirm that a message has been sent or that a configuration has been approved.

## References and source documents

- [American Concrete Pipe Association — Concrete Pipe Design Manual, 2014, Chapter 5: Pipe Joints, pp. 89–99](https://resources.concretepipe.org/hubfs/Resources/ACPA/Design/ACPA-Design-Manual-2014-Version.pdf)
- [American Concrete Pipe Association — Concrete Pipe Joints: performance requirements and joint functions](https://resources.concretepipe.org/concrete-pipe-joints)
- [ASTM C443-21 — Standard Specification for Joints for Concrete Pipe and Manholes, Using Rubber Gaskets](https://doi.org/10.1520/C0443-21)
- [Reliance — Internal Pipe Joint Seal brochure: components, material options, rubber widths and size range](https://reliancetrenchless.com/assets/doc/brochures/Reliance%20Internal%20Pipe%20Seal.pdf)
- [Reliance — Measuring Internal Pipe Joint Seals: bore, joint, seating, access and service records](https://reliancetrenchless.com/en-GB/resources/internal-pipe-joint-seals-measurement-guide)
- [Reliance — Internal Pipe Joint Seal DN150–DN4000: Seal Joints from Inside, No Digging](https://www.youtube.com/watch?v=OtA7ES9UKjc)