You've hit on a common practice and a good question. You're right, the primary reason for using RGS (Rigid Galvanized Steel) elbows when exiting the ground with PVC conduit is for physical protection of the conductors. Here's a breakdown of why it's done that way and the reasoning behind it

Reasons for RGS Elbows at Ground Exit:
Physical Protection from Impact

The area where conduit exits the ground is extremely vulnerable to physical damage. Lawn mowers, weed whackers, vehicles, shovels, and just general foot traffic can easily damage or crush PVC. RGS is far more resistant to impact.

UV Protection

While some PVC is UV-resistant, RGS provides absolute protection from the sun's degrading effects. Even UV-resistant PVC can become brittle over time, especially if exposed directly to sunlight.

Protection from Mechanical Stress

Movement of the ground (freezing/thawing, settling) can put stress on the conduit. RGS is much more rigid and can better withstand these forces, preventing cracks or breaks in the conduit.

Protection from Rodents and Pests

While not the primary reason, RGS offers better protection against rodents chewing through the conduit and damaging the conductors.

Grounding

If the conductors within the conduit are required to be grounded, the RGS conduit can sometimes provide a path for grounding, depending on local codes and the specific installation.

Code Requirements (Often Local)

While not universally mandated by the NEC (National Electrical Code), many local jurisdictions and utility companies require RGS for stub-ups out of the ground. Check your local codes.

Why Not RGS for All Bends Underground? Cost

RGS is significantly more expensive than PVC. Using RGS for all underground bends would substantially increase the cost of the installation.

Corrosion (Potentially)

While RGS is galvanized, it can still corrode over time, especially in certain soil conditions (high acidity, saline content, stray currents). PVC is inherently resistant to corrosion. Proper wrapping of any metallic conduit buried in the ground with tape is critical to preventing corrosion.

Installation Labor

PVC is much easier to cut, assemble, and glue than RGS. Using PVC for long runs and bends reduces labor costs.

Weight

RGS is much heavier than PVC, making installation more difficult, especially for long runs.

Less Need for Physical Protection

Once buried, the conduit is protected by the earth itself. The risks of impact and UV damage are significantly reduced.

Regarding Pulling Wire and Busting Through Elbows

You are correct that sharp bends can make pulling wire difficult and potentially damage the conductors. This is why:

Minimum Bending Radius

The NEC and good practices specify minimum bending radii for conduit to prevent damage to the wire during pulling. Whether you use PVC or RGS, you must adhere to these guidelines.

Large Radius Sweeps

Using large radius "sweeps" (either PVC sweeps or field-bent RGS) greatly reduces pulling friction and the risk of damage.

Lubricant

Wire pulling lubricant is essential for any long or complex pull, regardless of the conduit material.

Pulling Techniques

Proper pulling techniques (e.g., using pulling ropes, wire feeders) minimize stress on the conductors.

Inspection

Always inspect the conductors after pulling to ensure they have not been damaged.

In summary:

The use of RGS elbows at ground exits is a practical measure to protect the conductors in a vulnerable area. While pulling wire through any conduit requires careful planning and execution, the risk of damaging the conduit itself is significantly higher at the ground exit point, making the more robust RGS a worthwhile investment in that specific location.Always consult your local codes and the project specifications for specific requirements. If in doubt, err on the side of caution and use RGS where there is a higher risk of physical damage. Flag for review