# 255.121 Design of plastic pipe.

**Citation:** 16 NYCRR 255.121  
**Type / status:** regulation / current  
**Agency:** New York State Public Service Commission  
**Effective:** Not stated  
**Published:** Not stated

Transmission and Distribution of Gas. (a) Design formula. Design formulas for plastic pipe are determined in accordance with either of the following formulas:

P = 2StDF/(D − t)

P = 2SDF/(SDR − 1)

Where:

P = Design pressure, gauge, psig (kPa).

S = For thermoplastic pipe, the hydrostatic design basis (HDB) is determined in accordance with the listed specification at a temperature equal to 73°

## Document text

(a) Design formula. Design formulas for plastic pipe are determined in accordance with either of the following formulas:

P = 2StDF/(D − t)

P = 2SDF/(SDR − 1)

Where:

P = Design pressure, gauge, psig (kPa).

S = For thermoplastic pipe, the hydrostatic design basis (HDB) is determined in accordance with the listed specification at a temperature equal to 73°F (23°C), 100° F (38°C), 120°F (49°C), or 140°F (60°C). In the absence of an HDB established at the specified temperature, the HDB of a higher temperature may be used in determining a design pressure rating at the specified temperature by arithmetic interpolation using the procedure in Part D.2 of PPI TR-3/2012, (incorporated by reference, see section 255.7 of this Part). For reinforced thermosetting plastic pipe, 11,000 psig (75,842 kPa).

t = Specified wall thickness, inches (mm).

D = Specified outside diameter, inches (mm).

SDR = Standard dimension ratio, the ratio of the average specified outside diameter to the minimum specified wall thickness, corresponding to a value from a common numbering system that was derived from the American National Standards Institute (ANSI) preferred number series 10.

DF = Design Factor, a maximum of 0.32 unless otherwise specified for a particular material in this section.

(1) Except as provided in subdivisions (c) through (f) of this section, the design pressure for plastic pipe may not exceed a gauge pressure of 100 psig (689 kPa) for pipe used in:

(i) distribution systems; or

(ii) transmission lines in Class 3 and 4 locations.

(2) Plastic pipe may not be used where operating temperatures of the pipe will be:

(i) below -20°F (-29°C), or below -40°F (-40°C) if all pipe and pipeline components whose operating temperature will be below -20°F (-29°C) have a temperature rating by the manufacturer consistent with that operating temperature; or

(ii) above the temperature at which the HDB used in the design formula under this section is determined.

(3) Unless specified for a particular material in this section, the wall thickness of plastic pipe may not be less than 0.062 inches (1.57 millimeters).

(4) All plastic pipe must have a listed HDB in accordance with PPI TR-4/2012 (incorporated by reference, see section 255.7 of this Part).

(1) For PE pipe produced after July 14, 2004, but before January 22, 2019, a design pressure of up to 125 psig may be used, provided:

(i) the material designation code is PE2406 or PE3408;

(ii) the pipe has a nominal size (iron pipe size [IPS] or copper tubing size [CTS]) of 12 inches or less (above nominal pipe size of 12 inches, the design pressure is limited to 100 psig); and

(iii) the wall thickness is not less than 0.062 inches (1.57 millimeters).

(2) For PE pipe produced after January 22, 2019, a DF of 0.40 may be used in the design formula, provided:

(i) the design pressure does not exceed 125 psig;

(ii) the material designation code is PE2708 or PE4710;

(iii) the pipe has a nominal size (IPS or CTS) of 12 inches or less; and

(iv) The wall thickness for a given outside diameter is not less than that listed in the following table:

Pipe size (inches) | Minimum wall thickness (inches) | Corresponding SDR (values)
1/2″ CTS | 0.090 | 7
3/4″ CTS | 0.090 | 9.7
1/2″ IPS | 0.090 | 9.3
3/4″ IPS | 0.095 | 11
1″ CTS | 0.119 | 11
1″ IPS | 0.119 | 11
1 1/4″ IPS | 0.151 | 11
1 1/2″ IPS | 0.173 | 11
2″ | 0.216 | 11
3″ | 0.259 | 13.5
4″ | 0.265 | 17
6″ | 0.315 | 21
8″ | 0.411 | 21
10″ | 0.512 | 21
12″ | 0.607 | 21

(1) For PA-11 pipe produced after January 23, 2009, but before January 22, 2019, a DF of 0.40 may be used in the design formula, provided:

(i) the design pressure does not exceed 200 psig;

(ii) the material designation code is PA32312 or PA32316;

(iii) the pipe has a nominal size (IPS or CTS) of 4 inches or less; and

(iv) the pipe has a standard dimension ratio of SDR-11 or less (i.e., thicker wall pipe).

(2) For PA-11 pipe produced on or after January 22, 2019, a DF of 0.40 may be used in the design formula, provided:

(i) the design pressure does not exceed 250 psig;

(ii) the material designation code is PA32316;

(iii) the pipe has a nominal size (IPS or CTS) of 6 inches or less; and

(iv) the minimum wall thickness for a given outside diameter is not less than that listed in the following table:

Pipe size (inches) | Minimum wall thickness (inches) | Corresponding SDR (values)
1/2″ CTS | 0.090 | 7
3/4″ CTS | 0.090 | 9.7
1/2″ IPS | 0.090 | 9.3
3/4″ IPS | 0.095 | 11
1″ CTS | 0.119 | 11
1″ IPS | 0.119 | 11
1 1/4″ IPS | 0.151 | 11
1 1/2″ IPS | 0.173 | 11
2″ | 0.216 | 11
3″ | 0.259 | 13.5
4″ | 0.333 | 13.5
6″ | 0.491 | 13.5

(e) Polyamide (PA-12) pipe requirements. For PA-12 pipe produced after January 22, 2019, a DF of 0.40 may be used in the design formula, provided:

(1) the design pressure does not exceed 250 psig;

(2) the material designation code is PA42316;

(3) the pipe has a nominal size (IPS or CTS) of 6 inches or less; and

(4) the minimum wall thickness for a given outside diameter is not less than that listed in the following table:

Pipe size (inches) | Minimum wall thickness (inches) | Corresponding SDR (values)
1/2″ CTS | 0.090 | 7
3/4″ CTS | 0.090 | 9.7
1/2″ IPS | 0.090 | 9.3
3/4″ IPS | 0.095 | 11
1″ CTS | 0.119 | 11
1″ IPS | 0.119 | 11
1 1/4″ IPS | 0.151 | 11
1 1/2″ IPS | 0.173 | 11
2″ | 0.216 | 11
3″ | 0.259 | 13.5
4″ | 0.333 | 13.5
6″ | 0.491 | 13.5

(1) Reinforced thermosetting plastic pipe may not be used at operating temperatures above 150°F (66°C).

(2) The wall thickness for reinforced thermosetting plastic pipe may not be less than that listed in the following table:

Nominal size in inches (millimeters) | Minimum wall thickness in inches (millimeters)
2 (51) | 0.060 (1.52)
3 (76) | 0.060 (1.52)
4 (102) | 0.070 (1.78)
6 (152) | 0.100 (2.54)

## Provenance

- Official: Yes
- Source: <https://govt.westlaw.com/nycrr/Document/I505c6fe9cd1711dda432a117e6e0f345?viewType=FullText&originationContext=documenttoc&transitionType=CategoryPageItem&contextData=(sc.Default)>
- Source ID: `ny-dps-nycrr`
- SHA-256: `4768ca7f94bea40e682006a88cc24295713f49c722be9a96c60e0e300a331bd6`
- Retrieved: 2026-08-12T06:20:40.894Z
- Exported: 2026-08-23T17:02:03.634Z
- Document slug: `ny-nycrr-255-121`

### Source metadata

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  "title": 16,
  "part": "255",
  "partTitle": "Transmission and Distribution of Gas",
  "scopeKind": "gas-pipeline-safety",
  "tocPath": [
    "Part 255 Transmission and Distribution of Gas",
    "Pipe Design"
  ],
  "legalScope": "Complete current terminal legal unit exposed by the DPS-designated Title 16 NYCRR pipeline-safety part inventory.",
  "applicabilityCaveat": "Applicability depends on the part and section, Commission jurisdiction, commodity and facility type, intrastate or interstate status, operator and activity, exemptions, waivers, federal preemption, Commission orders, and incorporated law. DPS inspects portions of interstate systems for PHMSA, but PHMSA retains federal enforcement authority. DPS states that all jurisdictional Part 256 gas-holder and Part 257 LPG-plant facilities have been decommissioned even though those regulations remain unrepealed.",
  "incorporationCaveat": "These parts incorporate or rely on federal pipeline regulations, federal and New York statutes, Commission rules and orders, and privately authored technical standards. Part 10 supplies incorporation details. References metadata preserves explicit citations but does not reproduce external material, determine licensing rights, or decide whether a particular incorporation is static or dynamic.",
  "publicationCaveat": "The New York Department of Public Service identifies these eleven Title 16 NYCRR parts as its state pipeline-safety regulations and links to the public DOS/Westlaw NYCRR reading copy. That site labels the online text unofficial and directs users needing evidentiary accuracy to the Official NYCRR maintained by the Department of State Division of Administrative Rules. Each section's 'Current through' date is the most recent official NYCRR supplement covering that section, not a uniform corpus-wide amendment date.",
  "rights": "New York government-edict text is preserved with DPS, Department of State, and publisher attribution. The public reading site's presentation and enhancements, agency marks, forms, annotations, and incorporated federal or privately authored standards require separate rights review; this connector does not claim rights in those materials.",
  "rightsReviewRequired": true,
  "currentThrough": "2024-05-31",
  "historyEvents": "No event is emitted because the section reading copy does not supply an explicit adoption, filing, or effective-date history.",
  "publisherCitation": "16 CRR-NY 255.121",
  "identityAnomaly": null,
  "references": [
    {
      "citation": "16 NYCRR 255.7",
      "referenceType": "new-york-administrative-code",
      "url": "https://govt.westlaw.com/nycrr/Document/I505bfaaacd1711dda432a117e6e0f345?viewType=FullText&originationContext=documenttoc&transitionType=CategoryPageItem&contextData=(sc.Default)"
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