SDR 26 vs Schedule 40 Pipe

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SDR-26 and Schedule 40 pipe offer varying levels of wall thicknesses for piping frameworks. Both Schedule and SDR pipes have external diameters based on IPS (iron pipe standard), yet their internal diameters vary. SDR pipes of similar external diameter possess thicker or thinner wall thicknesses as compared to the same-sized Schedule 40 pipes. In this article, you’ll get familiar with SDR-26 pipe, Schedule 40 pipe, and the comparison (SDR 26 vs Schedule 40 Pipe) between both.

SDR 26 Pipe

SDR means standard dimension ratio and also is known as standard dimensional ratio. It is a standard that gives specific details regarding wall thicknesses and outer diameter across different PVC materials expected to achieve required pressure ratings. An SDR 26 means that the outside diameter (D) of the pipe is 26 times the wall thickness.

PVC SD 26 pipe
Courtesy: Supply Hog

The higher the SDR number, the lower the level of pressure it can handle. This is because a high SDR number indicates a great internal surface area is subject to the internal pressure. On the other hand, the lower the determined SDR, the higher the level of pressure it handles due to the higher wall thickness.

For instance, SDR-17 has a slender wall and lower pressure class as compared to SDR-11.  Understanding this value is fundamental for most applications including the following:

  • While determining inner pressure of piping for typical flow application
  • When embedding objects into a pipe framework like stiffeners for pressure fittings.
  • To understand pipe rigidity under extremely high pressure.
  • When evaluating the compressive strength of a buried pipe system.

SDR 26 Pipe Specifications

When it comes to SDR 26, the diameter (D) is 26 times the wall thickness. The pipe offers a wall thickness compared to the dimensional proportion of SDR 26 with the least pipe firmness value of 115 psi (790 kPa) when applied as per ASTM D2412 (Standard Test Method for Determination of External Loading). For this test, the basic length of the pipe is 14 feet without the inclusion of the bell.

Schedule 40 Pipe

This standard lays out the components of the Schedule 40 pipe. The pipe having the “Schedule” tag provides the same outer diameter and wall thickness no matter the piping material. Thus, a 2-inch-diameter across Schedule 40 PVC has the same outer diameter and wall thickness as any 2-inch diameter of Schedule 40 steel pipe.

Most commonly, PVC Schedule 40 pipe applies to lower water flow pressure applications and draining purposes. Schedule 40 PVC pipe can deal with up to 140 degrees F with regard to temperature. Pipe lengths are in standard 10′ or 20′ segments. Schedule 40 pipe is available in both plain end or belled end and needs no coupling for installation.

Schedule 40 Pipe Specifications

When it comes to schedule piping, the smaller the pipe diameter, the more stress the pipe may absorb since the wall thickness of the pipe is similar. Conversely, the bigger the pipe, the less stress it can take and the lower the pressure rating. For example, a 10″ schedule 40 can take handle up to 145 psi. But a 3/4″ Schedule 40 pipe clocks in at 480 psi.

SDR 26 vs Schedule 40 Pipe Properties

Diameter Ratio

SDR26 pipe has a specific pressure rate of 160 PSI. Each pipe measurement in a specific SDR is evaluated at the same pressure. This can be extremely helpful if you are creating a system with a variety of different pipe sizes working at a similar pressure throughout. On the other hand, Schedule 40 pipe has a changing proportion of wall thickness to the pipe diameter.

PVC Material

SDR 26 pertains to PVC material only, whereas the Schedule designation applies to a broad range of materials.

PVC material follows the requirements of ASTM D-1784, cell class 12454B, Type 1, Grade 1. Pressure pipe utilized in manufacturing should follow the ASTM D-1785 (Schedule 40/80) or ASTM D-2241 (SDR-26/41) and be recorded by the “National Sanitation Foundation (NSF)” for consumable water applications. Also, sheet stock material must follow ASTM D-1784, cell 12454B, Type 1, Grade 1, typical effect, fabricated without the utilization of fillers or plasticizers.

Assembly Procedures

PVC Schedule 40 fittings should be white in color. This color code applies to both drainage and pressure-based applications. While both the Schedule and SDR PVC pipe can be fusion welded, the more typical mode of assembly is PVC cement.

gluing PVC Schedule 40 pipe
Courtesy: Bob Vila

Flexibility Strength

The flexibility of SDR offsets the power of Schedule 40. SDR twists with the shifting and settling associated with underground installation. Having a higher flex resilience ensures fewer breaks from soil conditions. Whereas, Schedule 40 is inflexible to such an extent that if the ground moves or settles, the pipe incurs damage.