CSD and water are the two highest-volume PET applications. Their preforms look alike, but the engineering differs — swapping one for the other without re-validating risks burst failure or wasted resin.
The core difference: pressure
Carbonated soft drinks hold CO₂ pressure; still water does not. The CSD preform wall and base must resist that pressure across shelf life, which drives every other difference below.
| Still water | Carbonated (CSD) | |
|---|---|---|
| Neck | 29/25 · 48 mm · 55 mm | PCO 1881 · PCO 1810 |
| Weight | 9–668.5 g (light) | 15–53.6 g (heavier wall) |
| Resin IV | 0.76–0.80 dl/g | 0.84 dl/g |
| Bottle base | Standard / heel | Petaloid (pressure) |
Why you can’t swap
A water preform on a carbonated line can creep, deform at the base or fail under pressure; a CSD preform on water wastes grams and cost. Match the application first, then the neck and weight. Compare the actual references for each in the Product Finder, confirm the neck choice in 29/25 vs PCO 1881, and size the gram weight in the weight guide.