Pressure-Reduction Skids in Ontario: TSSA P-Numbers and PSTD Registration for Repeatable Packages

By Kopfkino Consulting Corp. · Published September 14, 2026 · Updated October 17, 2026 · 7 min read

TSSA's PSTD registration lets a standard pressure-reduction skid design be registered once and installed at multiple Ontario sites. How P-numbers, PSTD and the 2025 piping rules work.

Yes. Ontario's TSSA offers a P-standard (PSTD) registration: register a standard pressure-reduction skid design once and install it at multiple sites. Under the January 10, 2025 TSSA piping guideline, a PSTD number is issued to a Piping Certificate of Authorization holder for generic, repeatable designs. Each installation still requires site inspection and a test data report.

If you sell pressure-reduction skids (PRS) as a product line (same regulator train, pipe sizes and relief protection shipped site after site) registering every Ontario installation individually repeats the same engineering review. The Technical Standards and Safety Authority (TSSA) offers two tracks: a site-specific "P-number" and a "P-standard" (PSTD) number for repeatable designs, making compliance a fixed, per-model cost.

How does Ontario regulate pressure piping?

Under the Technical Standards and Safety Act, 2000 and O. Reg. 220/01, no person may manufacture piping for use in Ontario unless its design is registered with the director (s. 4(1)); starting construction before registration is at the applicant's risk (s. 4(2)).

A PRS is not registered as a single object; it decomposes into:

• Interconnecting piping: the P-number or PSTD registration;
• Fittings: regulators, valves, gauges, transmitters and relief valves each need an Ontario-valid fitting CRN; Ontario has no categorical fitting exemptions (unlike BC, Saskatchewan or Manitoba);
• Vessels: separators or filter housings exceeding the s. 2(2)(q)/(r) exemptions (over 1.5 ft³ / 42.5 L capacity, or over 6 in / 152 mm diameter) need their own vessel CRN.

The governing guidance is TSSA's Guidelines for Registration of Pressure Piping (P-standard included), January 10, 2025. Drawings must state construction code (ASME B31.1, B31.3 or B31.5, B31.9 is excluded), service fluid and B31.3 fluid-service category, design pressure/temperature, test pressure/type, and attestation that only registered fittings are used.

P-numbers versus PSTD: what is the difference?

The guideline defines:

• P-number: a registration number specific to the final installation; the default for engineered-to-order systems.
• PSTD number: a standard piping system design registration, issued to a Piping Certificate of Authorization (CoA) holder or responsible trade association. A PSTD design "can be used at any final installation locations" for designs routine in nature.

Annex A adds two conditions:

• Scope. A PSTD applies to shop-manufactured piping skids (possibly multiple fluid services, ideal for a gas PRS) or to single-service field-installation piping (multi-service field systems need a PSTD per service).
• Generic design. It must suit various owner/user site conditions, catalogue products, not bespoke projects.

PSTD does not eliminate installation-phase obligations: "piping installation according to P-standard designs still require inspections." Each installation is inspected, with a Piping Installation and Test Data Report countersigned by the Authorized Inspector (accredited manufacturers may use the Advisory BPV-001-23 Alternate Process).

What goes into a PSTD submission?

PSTD drawing and specification requirements match a site-specific registration, plus the Annex A conditions:

• Letter of application: CoA holder (the PSTD is tied to that name), contacts, drawing list, existing P- or PSTD numbers;
• P&IDs / flow diagrams for every pressure-retaining service, registration scope highlighted;
• GA and installation drawings: skid boundary, connection points, PRV locations, supports/anchors;
• Piping specifications and line list: line ID, NPS/schedule, material (ASME/ASTM spec and grade), fitting classification/rating, joining methods, NDE, support spacing;
• Bill of materials with fitting CRNs: every regulator, valve, gauge and PRD needs an Ontario-valid CRN or documented exemption (registered-fittings attestation mandatory);
• Relief valve settings and overpressure-protection basis;
• Design calculations, not required for routine wall-thickness selection per standard tables; TSSA decides for high pressure, temperature or special service.

P.Eng. involvement. O. Reg. 220/01 s. 4(3) requires an Ontario-licensed Professional Engineer's seal on boiler and vessel designs; practice extends P.Eng. expectations to piping: confirm your PSTD scope with TSSA.

Worked scenario: one PRS model, five Ontario sites

A US-based OEM sells a standardized 4-inch natural-gas PRS (600 psig inlet, 150 psig outlet, twin regulator runs, slam-shut, Category G relief valve) for Ontario distribution; five identical skids ship over two years.

• Without PSTD: each project needs its own P-number application and review, five submissions, five queues.
• With PSTD: the OEM (an Ontario Piping CoA holder) registers the design once and builds repeatedly; each site is still inspected with a test data report, but review happens once.

When is PSTD not appropriate?

Annex A excludes from P-standard eligibility:

PSTD also fits site-varying designs poorly: the registration covers one frozen design, and changes require a TSSA-accepted revision.

Fees and timelines (as of May 2025)

Per TSSA's BPV Fee Schedule v1.8 (effective May 1, 2025 - April 30, 2026), piping design registration is a flat $256.50 ($262.50 from May 1, 2026); engineering time bills at $213.00/hr beyond the included allowance, and expedited review costs 2×. Fitting registrations are $616.50 each. TSSA publishes no timeline; industry experience is roughly 6-16 weeks. Incomplete applications are not processed (since February 1, 2025), and information requests unanswered for 21 days can close the file.

How does PSTD compare to other provinces' skid programs?

Common mistakes

• Assuming PSTD waives site inspection: P-standard installations still require inspection and data reports.
• Unregistered fittings on the BOM. Ontario has no A/B/C/G categorical exemption; one unregistered regulator can stall the package.
• Submitting a site-engineered design as PSTD. Annex A limits P-standard to generic designs; owner-specific configurations need the P-number stream.
• Missing the 21-day response window on TSSA information requests; the file can be closed and the fee forfeited.

Best practices

• Freeze a genuinely standard bill of materials before applying; scope creep forces revisions. (Engineering recommendation)
• Pre-verify every fitting CRN for Ontario validity: the "5" designator or "C" suffix after the decimal. (Industry practice)
• Schedule inspection and data-report steps at every site: registration is once, inspection per installation. (Regulatory requirement)
• Engage an Ontario-licensed P.Eng. early; confirm sealing expectations with TSSA. (AHJ confirmation recommended)

Frequently Asked Questions

Can I register a standard pressure-reduction skid design once for repeated Ontario installations?

Yes: one PSTD number, held by a Piping CoA holder, covers a generic, repeatable shop-built design; each installation still requires inspection and a test data report.

What is the difference between a TSSA P-number and a PSTD number?

A P-number is installation-specific; a PSTD registers a standard design reusable at multiple sites, subject to Annex A's restrictions.

What makes a design ineligible for PSTD registration?

See the Annex A exclusion table above: steam, Class 300, NPS 12 gas and Category M/lethal-service limits apply.

How much does TSSA PSTD registration cost?

As of May 1, 2025, a flat $256.50 ($262.50 from May 1, 2026); expedited review is 2×.

Key Takeaways

• Ontario registers PRS piping through site-specific P-numbers or repeatable P-standard (PSTD) numbers under O. Reg. 220/01 and the January 10, 2025 TSSA piping guideline.
• PSTD suits generic, shop-built skid product lines and is held by a Piping CoA holder; per-site inspection and data-report obligations remain.
• Annex A's restriction list (steam limits, Class 300 ceiling, NPS 12 gas cap, lethal/Category M services) determines eligibility, screen early.
• Every fitting on the skid BOM needs an Ontario-valid CRN; Ontario has no categorical fitting exemptions.
• Fees are modest (flat $256.50 as of May 2025), but incomplete applications are refused and 21-day windows enforced.

Related Guides

• CRN Registration in Ontario: TSSA Requirements, O. Reg. 220/01 and the Mandatory P.Eng. Authentication
• CRN for Pressure-Reduction Skids: Piping Design Registration Essentials
• One Standard Package, Multiple Provinces: Designing Repeatable Skids for Canada-Wide Coverage
• Pressure Equipment Design Registration by Province: Regulators, Acts and CRN Processes Across Canada
• Ontario CRN requirements (TSSA)
• CRN for duplicate and series-production vessels

Sources

• O. Reg. 220/01 (Boilers and Pressure Vessels), https://www.ontario.ca/laws/regulation/010220
• TSSA, Guidelines for Registration of Pressure Piping (P-standard included), January 10, 2025, https://www.tssa.org/sites/default/files/2025-02/Guidelines%20for%20Registration%20of%20Pressure%20Piping-BPV-Jan10,2025-Guidelines.pdf
• TSSA BPV design registration and fee schedule, https://www.tssa.org/downloads/bpv-0
• TSSA fee change notice (effective May 1, 2026), https://www.tssa.org/important-information-fee-changes-effective-may-1-2026
• TSSA Fitting Registration Guidelines (Jan 2026, Rev 3), https://www.tssa.org/downloads/fittings-guidelines-jan-2026-rev-3
• TSASK IP-2016-07-04, Application for the Registration of a Skid Design, https://api.tsask.ca/wp-content/uploads/2024/07/IP-2016-07-04_-_Application_for_the_Registration_of_a_Skid_Design.pdf
• ABSA design registration, https://www.absa.ca/design-registration/

Structuring a PRS product line for Ontario (PSTD, site-specific P-numbers, or a hybrid) benefits from specialist support. Kopfkino Consulting assists PRS OEMs with CRN applicability assessments, registration strategy, pre-fabrication design review, calculations, PSTD and P-number submission packages, Ontario P.Eng. coordination, multi-province planning, and resolution of TSSA review comments. Regulatory decisions rest with TSSA; a well-prepared package reaches a decision with fewer cycles.

Contact us to discuss the registration scope for your equipment and its destination provinces.

Topics: CRN Registration, Ontario, TSSA, PSTD, Pressure-Reduction Skids