String-wound cartridges are made by winding polypropylene yarn around a core in a crisscross pattern. The layered structure holds a lot of dirt and keeps its shape at higher temperatures, so it is a good choice for warm water lines.
Key features
- Works with water up to 90 °C
- High dirt-holding capacity
- Standard 10 – 40 inch lengths
- Replace when pressure drop reaches 1 bar
Choosing and replacing cartridges
- How many cartridges? A standard PP cartridge (Ø60–64 mm) handles up to about 1.1 m³/h per 10 inches of length. For 20 m³/h, use a 5 × 40″ housing (22 m³/h) or a 7 × 30″ housing (23.1 m³/h).
- Filter rating: 5 µm is the usual choice before RO. Melt-blown, string-wound and carbon membrane cartridges are rated nominally; some RO membrane makers recommend 5 µm absolute, so tell our engineers if your RO system requires it.
- When to replace: when the pressure drop across the cartridge reaches 1 bar, or when a carbon cartridge is saturated. In front of RO membranes, DuPont recommends replacing cartridges at least every 3 months.
- Melt-blown or string-wound? Both are PP, 10″–40″, 5 µm. Melt-blown works up to 60 °C with a maximum pressure drop of 3.0 bar; string-wound works up to 90 °C with 2.7 bar.
- Big Blue or standard housing? Big Blue housings are Ø148 mm with 1″ ports for fat Ø110–115 mm cartridges, 0–4.5 m³/h (10″) or 0–9 m³/h (20″). Standard housings are Ø92 mm with 1/2″–3/4″ ports, 0–1.1 or 0–2.2 m³/h.
