The ROES-PH75 adds a 6th stage to the standard ROES-50 — a calcite-based pH+ filter that raises water alkalinity and restores calcium carbonate. Same NSF 58 certification, same proven APEC build quality, one extra stage. Here's whether it's worth the premium.
The ROES-PH75 typically costs $20–$40 more than the ROES-50. The alkaline stage noticeably improves water taste by raising pH from the slightly acidic 6.5–7.0 of standard RO to a more natural 7.0–7.5. For daily drinking water, this difference is real. For a refrigerator or ice maker hookup, it's less important. At the price difference, the upgrade is almost always worth it.
Standard 5-stage RO water is very pure but slightly acidic and mineral-free — the RO membrane strips out contaminants along with calcium and magnesium. The ROES-PH75's 6th stage runs the purified water through a calcite filter that dissolves small amounts of calcium carbonate back into the water, raising pH and adding a small amount of calcium.
The result is water that tastes more like natural spring water — rounder, less flat, with a naturally balanced pH. Independent taste tests consistently show people prefer the pH+ water side-by-side against standard RO.
| Filtration stages | 6 (with pH+ calcite filter) vs ROES-50's 5 |
| Output pH | 7.0–7.5 vs ROES-50's 6.5–7.0 |
| Calcium in output | Trace amounts added back |
| Filtration certifications | Same NSF 58 full-system certification |
| Flow rate | 75 GPD vs ROES-50's 50 GPD |
| Price difference | ~$20–$40 more than ROES-50 |
| Annual filter cost | Slightly higher — pH+ cartridge needed annually |
Note: the ROES-PH75 also uses a 75 GPD membrane vs the ROES-50's 50 GPD — it's both the alkaline upgrade and a faster membrane. Two improvements in one.