Why doesn't Unicel re-cover used D.E. grids? It certainly should be cheaper than buying a new set, and everybody wants to recycle, right?
That sounds good, but let's examine the facts. D.E. grids are made with a specially woven polypropylene cloth cover over a styrene plastic frame. In time, the plastic frame and grid cloth are oxidized by chlorine, weakened by acid and degraded by UV exposure.
Therefore, depending on maintenance, water temperature, and the chemical environment, grids can last anywhere from 6 months to 15 years (and longer).
How long will a re-covered grid last? How old is the frame? 6 months or 15 years? How brittle is the plastic? All you really know is that the fabric has failed. That's why the grid was re-covered. Since the frame was subjected to the same conditions as the fabric, can its failure be far behind?
But the re-covered grid looks new. The exposed collar is often sanded or polished to appear new. However, plastics are porous and when the skin is broken they absorb moisture, further weakening the frame. In addition, some re-covered grids are made from two or more broken frames which have been cut and glued together. Can you be sure the reassembled grid is the correct length? One grid out of spec will result in D.E. bypass.
A recovered grid may be cheaper, but can you really afford it?