1. **What is the difference between D2729 and SDR35?**
* **D2729** refers to ASTM D2729, a specific industry *standard* for Polyvinyl Chloride (PVC) sewer pipe and fittings. It defines requirements for dimensions, material properties, and performance.
* **SDR35** (Standard Dimension Ratio 35) is a *dimensional classification* for pipe based on its wall thickness relative to its outer diameter. Pipes meeting the ASTM D2729 standard are *typically* manufactured to the SDR35 dimension ratio. So, D2729 is the standard, and SDR35 is the common dimension used within that standard for gravity sewer applications.
2. **Is SDR35 stronger than Schedule 40?**
* It depends on the context:
* **For Pressure:** Schedule 40 PVC pipe has a much higher pressure rating (e.g., ~150-220 PSI for 4") than SDR35 PVC (which is rated for non-pressure, gravity flow only). Schedule 40 is significantly stronger for pressure applications.
* **For Rigidity/Stiffness:** SDR35 PVC pipe generally has a higher Pipe Stiffness (PS) rating (around 46 PSI) compared to Schedule 40 PVC (around 55-60 PSI for 4"). This means SDR35 is slightly *less rigid* and more flexible than Schedule 40 PVC pipe of the same nominal size. Schedule 40 is structurally stiffer.
* **Material Matters:** Schedule 40 pipe can be PVC or ABS. ABS Schedule 40 has lower stiffness than PVC Schedule 40 and is generally less rigid than PVC SDR35.
3. **What is an ACO pipe?**
* An **ACO pipe** (or more commonly **ACO drain** or **channel drain**) refers to a type of linear drainage system designed to collect surface water runoff over a length. It consists of a narrow, trench-like channel body (often concrete or polymer concrete) covered by a grate. ACO is a prominent brand name that has become synonymous with this type of product, similar to how "Kleenex" is used for tissues. Its primary use is for driveways, patios, pool decks, and other paved areas.
4. **Which is stronger, SDR 26 or SDR35?**
* **SDR26 is structurally stronger (stiffer) than SDR35.** The SDR number represents the ratio of the pipe's outer diameter to its wall thickness. A *lower* SDR number means a *thicker* wall relative to the diameter. Therefore, SDR26 pipe has thicker walls than SDR35 pipe of the same diameter, making it more rigid and able to withstand higher external loads (like deep burial or heavy traffic).
5. **What is SDR 26 pipe used for?**
* **SDR26 PVC pipe is primarily used for gravity-flow sewer and drainage applications** where exceptionally high external load resistance is required. This includes:
* Deep burial sewer lines (deeper than standard SDR35 installations).
* Areas under heavy traffic loads (like major roads or airports) without requiring concrete encasement.
* Situations requiring extra strength against soil pressure or potential impact.
* It is governed by standards like ASTM D3034 (for smaller diameters) or ASTM F679. Like SDR35, it is *not* designed for pressure applications.
