The ROES-50 uses standard 10" × 2.5" filter housings. Here's exactly what to order, in what quantities, and where to buy to avoid compatibility issues.
| Sediment filter (Stage 1) | 1× 5-micron PP sediment — every 6–12 months |
| GAC carbon filter (Stage 2) | 1× granular activated carbon — every 12 months |
| Carbon block filter (Stage 3) | 1× CTO carbon block — every 12 months |
| Post-carbon filter (Stage 5) | 1× inline post-carbon — every 12 months |
| RO membrane (Stage 4) | 1× ROES-50 compatible — every 2–3 years |
APEC packages all the annual filters (Stages 1, 2, 3, 5) into a single replacement set. Order once per year, replace all at one session, done. The RO membrane is a separate order every 2–3 years.
The ROES-50 uses standard sizing (10" × 2.5" for pre-filters) that many brands make. Third-party filters can work and may cost less, but APEC's NSF 58 certification applies only to their own genuine filter sets. Using third-party filters may affect both filtration performance and warranty coverage.