Is recycled glass really a better filter media than sand? Poolrite partnered with Griffith University's Industrial Affiliates Program to find out, comparing Diamond Kleen with sand and zeolite in theory and in the lab. Here's what the study found.
A media filter cleans your pool by trapping dirt in the spaces between grains, and the grains are usually sand or zeolite. In 2011, a Griffith University engineering project compared Diamond Kleen M10 recycled glass with both. The media were first compared using three standard filtration models. Then each was tested in a purpose-built filter column, using standard ISO test dust, measuring how quickly the water cleared, the pressure across the filter bed and the size of the particles left behind.
Final turbidity after the filter run
Lower is clearer. FTU measures cloudiness.
The Diamond Kleen column gave the best turbidity reduction, reaching 0 FTU after 47 hours. Sand took 55 hours to reach 2 FTU, and zeolite was still at 155 FTU after more than 52 hours.
The glass test also started with lower turbidity (1,200 FTU against 2,150 for sand), which the report notes may have helped.
In the sand column, dirt collected mostly at the top and bottom. It formed a "cake" on the surface that screened the flow, and the sand bed visibly compacted. In the Diamond Kleen column, particles were captured all the way through the bed, with limited compaction. Zeolite only collected particles at the bottom.
Under the microscope, the glass grains are sharper and more angular than sand. That leaves more open space in the bed (porosity of 0.42 for Diamond Kleen M10 against 0.39 for sand), and the filtration models predict that this helps the glass perform slightly better than sand, with both well ahead of the zeolite tested.
| Measure | Diamond Kleen M10 | Sand | Zeolite |
|---|---|---|---|
| Starting turbidity | 1,200 FTU | 2,150 FTU | 1,450 FTU |
| Filter run time | 47 hours | 55 hours | 52+ hours |
| Final turbidity | 0 FTU | 2 FTU | 155 FTU |
| Pressure change across the bed | −0.2 psi | +0.3 psi | No change |
| Bed porosity | 0.42 | 0.39 | 0.44 |
| Grain size | 1.18 mm | 1.3 mm | 1.6 mm |
“Based on the results the glass media (DK M10) was deemed more efficient theoretically and experimentally than traditional sand and zeolite media for use as swimming pool granular filtration media.”
Campbell, Griffith University, 2011
Made from crushed, recycled glass bottles, giving waste glass a second life in your pool.
Grain size 0.75–1.7 mm. The main filtering layer at the top of the bed.
Grain size 1.7–3.0 mm. The support layer at the bottom of the filter.
Use in place of sand in media filters, including Poolrite S-Series. Comes in 15 kg bags.