APEC Water Systems ships replacement filters from its California warehouse with 2-business-day delivery to most of the continental US. Unlike most RO brands, APEC's replacement parts are also available on Amazon -- typically fulfilled by APEC directly rather than third-party sellers -- reducing the risk of counterfeit or incompatible cartridges. This guide covers every filter for every current APEC RO model with part numbers, replacement intervals, and annual cost.
ROES-50 filter replacement schedule
| Stage | Filter type | APEC part number | Interval | Cost |
|---|---|---|---|---|
| Stage 1 | 5-micron PP sediment | FI-SET-ROES-50 (set) | 6-12 months | $35-$50/set (stages 1-3) |
| Stage 2 | 10-micron carbon block | (included in set) | 6-12 months | -- |
| Stage 3 | 5-micron carbon block | (included in set) | 6-12 months | -- |
| Stage 4 | TFC RO membrane | RO-90 or APEC-MEMBRANE-90 | 24-36 months | $30-$50 |
| Stage 5 | GAC carbon post-filter | FF-10-GAC | 12 months | $12-$18 |
Annual cost estimate: $55-$75 (stages 1-3 set + post-filter annually; membrane amortized over 2.5 years = ~$15/yr)
ROES-PH75 filter replacement schedule
| Stage | Filter type | APEC part number | Interval | Cost |
|---|---|---|---|---|
| Stages 1-3 | PP + carbon block set | FI-SET-ROES-PH75 | 6-12 months | $35-$50/set |
| Stage 4 | 75 GPD TFC membrane | RO-TFC-1812-75 | 24-36 months | $35-$55 |
| Stage 5 | GAC post-filter | FF-10-GAC | 12 months | $12-$18 |
| Stage 6 | Calcite remineralization | FL-CALK | 12 months | $20-$30 |
Annual cost estimate: $75-$100 (stages 1-3 set + post-filter + calcite annually; membrane amortized)
WFS-1000 filter replacement
| Stage | Filter type | APEC part number | Interval | Cost |
|---|---|---|---|---|
| Stage 1 | 5-micron PP sediment | FI-SET-WFS-1000 (set) | 12 months / 1,000 gal | $28-$40/set |
| Stage 2 | 10-micron carbon block | (included in set) | 12 months | -- |
| Stage 3 | 5-micron carbon GAC | (included in set) | 12 months | -- |
How to know when to replace
- Pre-filters (stages 1-3): Change on schedule regardless of appearance. A visually clean carbon block can be exhausted for chlorine removal long before it looks dirty. For high-turbidity source water (well water, sandy municipal), change the sediment pre-filter every 6 months; the carbon blocks can go 12 months.
- RO membrane: Monitor output TDS with the included TDS meter. If output TDS rises above 15-20% of source water TDS, the membrane is declining. Replace before it exceeds 25% -- a failing membrane is stressing itself and the housing unnecessarily.
- Post-filter / calcite: Change at 12 months. The GAC post-filter is the last line of taste defense; an exhausted post-filter passes faint chemical notes that undermine otherwise clean RO output.
Where to buy genuine APEC filters
- APEC directly (apecwater.com): Best pricing, fastest California shipping, guaranteed genuine
- Amazon -- APEC Water Systems storefront: Convenient, APEC-fulfilled, Prime eligible
- Avoid: Third-party Amazon sellers with non-APEC branding selling "compatible" filters -- these vary in quality and some use inferior membrane material with lower real-world rejection rates than genuine APEC membranes
Annual maintenance checklist
- Replace pre-filter set (stages 1-3) -- 6-12 months
- Replace post-filter (stage 5) -- 12 months
- Replace calcite cartridge if ROES-PH75 (stage 6) -- 12 months
- Check storage tank bladder pressure -- should read 6-8 PSI when tank is empty and system is shut off
- Run a hydrogen peroxide sanitization cycle -- annually, using 3% H2O2 through the pre-filter housing before installing new filters
- Check all compression fittings for weeping -- tighten as needed