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Technical FAQs

Frequently Asked Questions about PVC

General PVC

There are no governing bodies that require specific color coding; therefore, the PVC pipe industry has
self-standardized color coding of PVC pipe. Below is the typical industry color coding standard of PVC

Blue Pressurized potable water
Green Sewer, both gravity and force main
Purple Reclaimed (non-potable) water
White General use – (plumbing, Drain/Waste/Vent, or Water well)
Gray General use – (typically plumbing and electrical)


  • There is no regulation of the actual shade of color used. Therefore, based on the manufacturer, the
    specific color may have slightly different shades. For example, NAPCO's Green PVC sewer may have
    a slightly different shade than other manufacturers.
  • The color of the pipe material does not affect the pipe performance.

The following physical properties of the pipe must be regularly tested in order to be certified to
AWWA C900: Sustained pressure, Burst pressure, Hydrostatic pressure integrity, Flattening, Extrusion
quality (Acetone Testing) and Ring-tensile test. The testing of these physical properties assures the
product quality of the finished products has not deviated from the design specifications.

For information about the testing required by AWWA for certification of PVC pipe and fittings, refer to
Uni-Bell's Technical Brief: AWWA Standards for PVC Pipe: Product Testing

Note: similar testing is required for ASTM D2241 PVC Pipe.

Please contact Technical Services at 855-624-7473, Option 3 or for more

Our PVC pipe is produced in the United States of America and in Canada.

PVC pipe sold in the USA is manufactured at facilities located only in the U.S. PVC Pipe sold in Canada
is manufactured at facilities located in the U.S. and Canada. All of NAPCO’s locations can be found here

Also, find our "Made in USA Certification" letter, located here

The PVC Pipe Association, A.K.A. Uni-Bell, estimates a design life expectancy of 100 years but in reality that estimate could be far exceeded. The 100 year estimate is primarily based upon engineering analysis of fatigue in PVC pipe wall, which is highlighted in numerous reports and independent studies, which are listed below. Also, Uni-Bell has various technical papers and articles that discuss PVC service life expectancy for water and sewer systems. These articles and papers are available, publicly and free of charge, on Uni-Bell's website

The direct links to a few of Uni-Bell's resources and reports are located below:

Dimension Ratio (DR) and Standard Dimension Ratio (SDR) both refer to the same ratio, (Outside
Diameter [OD] / Wall Thickness) – Refer to Figure 1 below.

DR Explained

Figure 1 - OD/t Ratio


For more information refer to the following link: Dimension Ratio (DR) Explained for PVC Pipe

The only difference between Schedule 40 & Schedule 80 is the wall thickness. The wall thickness also directly correlates with the pipe’s pressure rating. Schedule 40 (usually white) has a thinner wall thickness and therefore a lower pressure rating than Schedule 80 pipe (usually grey). Schedule 40 and 80 PVC pipe does not use the Outside Diameter / wall thickness ratio that DR and SDR use; therefore, the Schedule 40 and 80 pressure ratings are different for each pipe diameter size and must be looked up for every diameter and Schedule combination. NAPCO’s PVC Plumbing pipe (ASTM D1785) is available in both Schedule 40 and Schedule 80.

Refer to the applicable Technical Product Specification for more details on wall thickness and
pressure ratings for our PVC plumbing pipe. Technical Product Specification link here

CIOD stands for Cast Iron Outside Diameter and is the diameter standard used for AWWA C900 PVC pipe (e.g., blue potable water pipe). IPS is Iron Pipe Size, also known as DIPS or Ductile Iron Pipe Size, and is the diameter standard used for ASTM D2241 PVC pipe. (Note, other diameter standards do exist, such as, PSM – Sewer, PIP – Irrigation, Schedule 40/80/120 – Plumbing & Water Well)

Also, consider the following:

  • Aside from compatibility with existing connections, there is no distinct advantage of using one pipe diameter standard over the other.
  • No two are directly interchangeable.

No. According to AWWA M23: PVC Pipe - Design and Installation Manual of Water Supply Practices,
there is a zero leakage allowance. There is a make-up water allowance designated during acceptance
testing of PVC pipe, as detailed in AWWA M23; however, that is NOT to be misinterpreted as
“allowable leakage” of in-service PVC pipe.

The make-up water allowance during testing is in place to allow for the following:

  • Make-up for entrapped air
  • Make-up for movement due to seating of valves, joint restraints, etc.
  • Make-up for slight increase in pipe diameter due to internal pressures

Refer to Uni-Bell’s Technical Brief for more details on AWWA’s stance on zero leakage in PVC pipe here

NAPCO provides a separate limited warranty for different product lines. The warranties can be found
at the following link:

PVC Pipe Design

The NSF 61 listing establishes the health effects requirements for the chemical contaminants
and impurities that are indirectly imparted to drinking water from products, components and
materials used in drinking water systems.

The NSF 14 listing pertains to the minimum physical, performance health effect, quality
assurance, marking and recordkeeping requirements for plastic pipe components. These
requirements are determined acceptable by various tests performed by NSF on PVC pipe
samples from the manufacturer.

Common engineering practice suggests a maximum flow velocity of 5 ft./s during normal (steady state) operating conditions for pressure pipe application. During surge conditions the recommended maximum allowable flow rate is 10 ft./s. Exceeding the recommended maximum flow velocity, for an extended period of time, could result in excessive internal pressures in the PVC pipe system, possibly leading to a joint or pipe wall failure.

For gravity sewer lines, which are not pressurized, the recommended maximum flow velocity is 10 ft./s before special considerations need to be taken for energy dissipation and internal erosion prevention.

Source: PVC Pipe Association: Handbook for PVC Pipe Design and Construction, 5th Ed.

Consider the following concepts when designing and installing PVC pipe in cold-weather environments:

  • The tensile strength and modulus of elasticity are not negatively impacted.
  • Impact strength may decrease to approximately 70-90% of PVC’s strength at an ideal temperature of 73.4°, dependent on actual temperature.
  • All PVC pipe should be installed at least 12" below the frost line.
  • Gasketed joints may require a slightly higher force to assemble.
  • Proper installation practices become more important in cold weather conditions compared to moderate temperatures.
    • Proper installation practices include: handling pipe more carefully, proper lubrication and proper insertion of the spigot into the bell.

For more information, refer to Uni-Bell's Technical Brief: Cold Weather: No Practical Effect on PVC Pipe Installation and Use

PVC pipe works great for conveying water and sewage. PVC pipe may be exposed to various chemicals via direct contact with soil contamination or via chemicals in the fluids inside the pipe. The concentration of the chemical is important when considering chemical resistance.

General Resistivity of Typical Gasket Materials

Common Name

Styrene Butadiene Rubber (SBR) & IR (Isporene Rubber)/SBR Blend

Nitrile Buadiene Rubber (NBR)

Ethylene Propylene Diene Monomer (EPDM) Rubber

General Properties

Resistance to water
absorption. Excellent
elongation. Standard
material used for all
Resistant to Petroleum-
based fluids. Good
mechanical performance.
Resistant against
Ozone, aging, and most
chemicals. Poor
resistance to mineral
and petroleum-based

Resistant To

- Alcohol
- Most moderate
- Organic Acids
- Ketones / Acetone
- Aldehydes
(I.E., Formaldehyde)

-Silicone Greases / Oils
- Petroleum Oils / Fuels
- Fats
- Hydraulic Fluids

-Animal and
vegetable oils
- Ozone & UV
- Brake fluids
- Strong and
oxidizing chemicals
(Peroxides, Nitrates,

Attacked By

-Most Solvents & Oils

-Concentrated Acids

-Ketones (I.E., Acetone)
- Halogenated
Hydrocarbons (I.E.,
Chloroform, Halon)
- Brake fluids
- Strong acids
- Ozone / weathering

-Mineral oils
- Petroleum Oils
- Fuels

*Note: NAPCO does not offer Neoprene gaskets as of 12/2019

There is also a detailed Chemical Resistivity chart available in Chapter 3 of the Handbook of PVC Pipe Design and Construction by Uni-Bell. Three chapters are available for free download.

If you have a specific question about chemical compatibility, please contact Technical Services at 855-624-7473, Option 3 or

Exposure to sunlight can cause slight fading of PVC pipe surfaces. PVC pipe has not shown degradation of performance when exposed to sunlight for periods of time, up to two years. Physically blocking the UV energy from reaching the pipe surface prevents the fading. Methods of covering the pipe could include: permanently covering (‘wrapping’) the pipe, or painting with a light-colored paint that is chemically compatible with PVC (I.e., water based acrylic or latex).
NAPCO's Yelomine product line provides superior long-term UV protection and can be used outdoors. Yelomine contains an increased amount of high-purity TiO2 that is specially formulated to resist the effects of UV exposure.
Refer to NAPCO's Technical Bulletin: Ultraviolet (UV) Radiation Exposure of PVC Pipe Products

The length of PVC pipe expands and contracts with temperature change. The change in length is based
upon material properties and amount of temperature change.

The change in length of pipe per 10°F ΔT PVC pipe is reflected below:

Pipe Length

Ft (m)

Length Change

In. (mm)

100 (30.48)

0.36 (9.15)

20 (6.1)

0.072 (1.83)

14 (4.3)

0.050 (1.27)

10 (3.0)

0.036 (0.91)


For example, a length of 1,760 ft of PVC pipe with an initial installed temperature of 73°F and an operating
temperature of the pipe will be 83°F. The change of length over the entire length of pipe at operating
temperatures will be ~6.34”.

Source: PVC Pipe Association. Handbook of PVC Pipe Design and Construction, 5th Ed. New York: Industrial
Press, 2013. Print.

Note: Some pipe systems may require additional accommodation of thermal expansion and contraction
movement, than the standard integral bell joint can provide. In these cases, NAPCO offers expansion joints
up to 6” diameter.

The maximum operating temperature of PVC pipe is 140°F. The pipe’s pressure rating, and other
performance characteristics, must be de-rated for all temperatures above 73.4°F (23°C); refer to the table
below for the appropriate de-rating factors (Source: Handbook of PVC Pipe Design and Construction, Fifth
Published by PVC Pipe Association).

Maximum Service Temp °F (°C)
Multiply pressure class at 73.4°F (23°C) by factor shown

80 (27)


90 (32)


100 (38)


110 (43)


120 (49)


130 (54)


140 (60)




  • For temperatures in between those listed above, interpolate between the two closest temperatures to
    determine the specific de-rated pressure class.
  • Pipe gaskets are typically not affected at the temperatures listed above.
  • The de-rating factors assume sustained elevated service temperatures. When the contents of a PVC
    pressure pipe are only intermittently and temporarily raised above the service temperature shown, de-
    rating may not be needed.

The maximum burial depth is the maximum depth the pipe can be buried without the pipe deflecting
more than 7.5% for gravity sewer or 5% for pressure pipe. Some municipalities require a maximum pipe
deflection of 5% regardless of pipe type. Maximum burial depth depends on multiple factors such as
pipe stiffness, bedding material and compaction (Soil Modulus - E'), and the presence of any additional
above ground live loads.

Please refer to the following Technical Bulletin: Burial Depth Guidance for Gravity Sewer PVC Pipe

According to ASTM D2321, Standard Practice for Underground Installation of Thermoplastic Pipe for
Sewer and Other Gravity-Flow Applications:

“The minimum depth of cover should be established by the engineer, based on an evaluation of
specific project conditions.”

“In the absence of an engineering evaluation, the following minimum cover requirements should be
used. For embedment materials installed in accordance with Table 3, provide cover (that is, depth of
backfill above top of pipe) of at least 24 in. or one pipe diameter (whichever is larger) for Class I
embedment, and a cover of at least 36 in. or one pipe diameter (whichever is larger) for Class II, III, and
IV embedment, before allowing vehicles or construction equipment to traffic the trench surface, and at
least 48 in. of cover before using a hydro-hammer for compaction.”

Also, the Uni-bell PVC Association Handbook of PVC pipe states:

“A minimum cover height of 12 in. is recommended for PVC (SDR35) pipe subjected to highway loads of
up to 18 kip axle. To prevent cracking of the road surface, special attention should be given to the
selection, placement, and compaction of backfill material around shallow buried flexible pipe (such as
PVC pipe)”

Please refer to the following Technical Bulletin: Burial Depth Guidance for Gravity Sewer PVC Pipe

In regards to PVC pressure pipe the minimum burial depth is typically driven by the depth of the frost line.
Where there is no frost line, the minimum burial depth for PVC pressure pipe is 12”.


Buried vs Embedded Pipe

Source: PVC Pipe Association. Handbook of PVC Pipe Design and Construction, 5th Ed.

New York: Industrial Press, 2013. Print.


PVC Pipe Installation and Testing

We recommend that the bell end be stationary and the spigot (Male End) be inserted into the bell
end, as seen below. This reduces the risk of debris entering the bell prior to installation.


bell direction

Typically it is recommended that the bell direction is installed such that the fluid flows from the spigot
end into the bell end, as seen below; however, the direction of the bell is not critical and the joint will
seal regardless of flow direction.


Bell Direction Fluid Flow

Allowable angular joint deflection of NAPCO's pipe is as follows:


Joint Type
Max. Angular Joint Deflection
Integral Bell (IB)
Certa-Lok RJ Coupling

0.5° per side

1° Total per joint

Certa-Lok RJIB 0.5°
Solvent Weld (SW) None


For more information on joint deflection and details about longitudinal bending of PVC pipe refer
NAPCO's Technical Bulletin: Changing Direction of PVC Pipelines

Allowable angular joint deflection for NAPCO Royal pipe:


Joint Type
Max. Angular Joint Deflection
Pressure Pipe – Integral Bell (IB)

1° (100mm to 300mm [4” to 12”])

2° (350mm to 600mm [14” to 24”])

Gasketed Sewer – Integral Bell (IB)

5° (100mm to 300mm [4” to 12”])

3° (375mm to 600mm [15” to 24”])

1.5° (600mm [27”])


5° (200mm to 450mm [8” to 18”])

3° (525mm to 600mm [21” to 24”])

1° (750mm to 900mm [30” to 36”])

Cobra Lock RJ Coupling N/A – Refer to Max. Bending Limits


For more information on longitudinal bending of Cobra Lock® refer to the product’s Technical Specification

For more information on changing direction of NAPCO Royal’s Gasketed Sewer Pipe and Kor-Flo® refer to the
Gasketed Sewer Pipe and Fittings Installation Guide (Page 19 and 20)

CCTV inspection of PVC pipelines can reveal small longitudinal gaps between the spigot end and the
end of the bell of gasketed joints. These gaps are designed to accommodate expansion, deflection,
and slight over-insertion. This gap does not affect the hydraulic performance of the pipe.

Note: Pictures and videos from CCTV inspections cannot be used to determine exact measurements of
joint gaps due to viewing angles and camera lighting.


Example of typical gap in joint:


Expansions Gap in Joint


For more information, refer to Uni-Bell's Technical Brief about Expansion Gaps

PVC Pipe should not be air tested at high pressures!

A. PVC Pressure pipe requires pressure testing at high psi. A failure of a high pressure air testing
would result in high velocity and likely fatal projectile objects; therefore, air testing of PVC
pressure pipe is expressly prohibited. Water pressure testing is the only pressure testing
allowed to be performed on PVC pressure pipe.

B. Gravity Sewer PVC pipe (ASTM D3034/F679) can be air tested up to a maximum of 9 psig
(typical testing pressures are lower) according to ASTM F1417 "Standard Test Method for
Installation Acceptance of Plastic Gravity Sewer Lines Using Low-Pressure Air.” Even though 9
psig is low pressure, the resulting thrust forces on a pipeline, end plugs and caps can result in
projectile objects during a test failure; therefore, the following safety risks from Section 6 of
ASTM F1417 (the ASTM Air Testing Standard) should be considered:

  • “No one shall be allowed in the manholes during testing”
  • “When lines are tested, it is mandatory that all the caps and plugs be braced as an
    added safety factor”
  • “A regulator or relief valve set no higher than 9 psi shall be included on all
    pressurizing equipment.”

For more information, refer to Uni-Bell's Technical Briefs: Air Testing of Installed PVC Pipelines and Considerations for Air Testing of PVC Sewer Pipes


PVC Pipe Gasket

Water tight joints – When installed correctly, gasketed joints are leak-free, allowing for
successful post-installation testing and a leak-free piping system.

Ease of Installation – Gasketed joints require minimal time to install, especially compared to
solvent weld, flanged, or welded joints. The gasketed joints can be easily pushed together and
are ready for use immediately following assembly.

Pipeline System Robustness Gasketed joints allow for additional movement, within the joint,
due to joint deflection, minor surge pressures, and thermal expansion/contraction. Note:
restrained joints may be required when excess force is expected to occur at the joints.

NAPCO offers the following gasket materials:

  • Styrene Butadiene Rubber (SBR) – Typically the standard offering
  • Nitrile (NBR)
  • Ethylene Propylene Diene Monomer (EPDM) Rubber

If you have a specific question about available gasket materials, please contact Technical Services at
855-624-7473, Option 3 or

Note: gasket types are specific to product types

Gasket Types

Certa-Lok® Joint

NAPCO’s Certa-Lok® self-restraining pipe system provides a restrained joint by utilizing precision-
machined grooves on the pipe spigot and inside the pipe bell or coupling. When assembled, a spline is manually
inserted or imbedded in the pipe bell, or coupling, engages a grove in the spigot resulting in a
continuous circumferential restrained joint that locks the segments of pipe together.  A flexible
elastomeric gasket located in a groove in the pipe bell, or coupling, provides a hydraulic pressure seal.

Certa-Lok® is available with a Restrained Joint (RJ) coupling or with a Restrained Joint Integral Bell

The advantages of the Certa-Lok joints are:

  • Quick and easy joint installation
  • Tensile strength in BOTH directions (PUSH and PULL), excluding CLIC
  • Corrosion protection is not required
  • Provides an a restraint system within the OD of the pipe system
  • Eliminates the need for external restraints and thrust blocks (as applicable)


The Certa-Lok self-restraining joint is used in the following Product lines:


Product Line
Joint Type Available
C900 Pressure Pipe RJIB and RJ Couplings
D2241 Pressure Pipe RJ Couplings Only
Certa-Flo® - Sewer RJIB Only
Certa-Com® - Electrical RJIB Only
Certa-Set® - Agriculture & Irrigation RJ Couplings Only
D2241- Yelomine® RJIB and RJ Couplings
Certa-Lok® Well Casing RJIB and RJ Couplings
Certa-Lok® Drop Pipe RJ Couplings Only


NOTE: RJ Coupling = Restrained Joint Coupling; RJIB = Restrained Joint Integral Bell






C900 RJ

All tensile force ratings can be found in the Technical Product Specification of the applicable product
line (Yelomine, C900, 2241, Well Casing, Certa-Flo, Certa-Com, Etc.). For more information on
NAPCO's process of Tensile Testing our products, refer to the following Technical Bulletin: Certa-Lok® Joint Tensile Strength Testing

In most cases RJ couplings and pipe can be used with RJIB pipe, but there are circumstances where
they are not compatible. Refer to following Technical Bulletins for connecting different style joints for
more specific scenarios.


For our C900 product line refer to: Connecting Different Joint Styles of AWWA C900 PVC Pipe

For our ASTM D2241 product line refer to: Connecting Different Joint Styles of ASTM D2241 PVC Pipe

NAPCO's Yelomine® products use a specially modified PVC compound* that contains impact modifiers
that allow for higher impact strength and ultraviolet (UV) inhibitors that allow the pipe to be used
continuously in exposed above-ground applications. Yelomine® PVC is certified to the specifications of
ASTM D2241.

*Minimum cell classification of 12454, as defined in ASTM D1784.

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