WHAT DOES REVERSE OSMOSIS REMOVE?

A certified under‑sink RO (with carbon pre‑/post‑filters) is built to reduce:

• Dissolved salts (TDS) & metals such as lead, arsenic, chromium, copper, sodium. (Verify model‑specific claims on the performance data sheet.) CDC

• Nitrate/nitrite and fluoride (yes—RO lowers fluoride). CDC

• PFAS (“forever chemicals”)—RO is one of EPA’s listed effective home treatments. Choose a unit with certifications covering PFOA/PFOS claims. US EPA+1

• Microorganisms (parasites, bacteria, viruses) when the system is properly designed and maintained. Municipal water is already disinfected; RO adds a barrier at your kitchen tap. CDC

• Microplastics—membrane barriers (including RO) substantially reduce them in drinking‑water treatment; multiple studies support high removal. Iris+1

Proof standard: Look for NSF/ANSI 58 on the product label (the RO standard). Many high‑efficiency units now also carry EPA WaterSense labeling (requires NSF/ANSI 58 plus efficiency and membrane‑life criteria). NSF+1

NASHVILLE (METRO WATER SERVICES) – CUMBERLAND RIVER SOURCE

• Hardness: ~100.5 mg/L (moderately hard).

• Chlorine residual: ~0.8–2.7 mg/L (avg 1.70).

• Fluoride (added): ~0.68 mg/L (range 0.61–0.75).

• DBPs: TTHM LRAA 44.8 ppb (range 14.2–65.3), HAA (HAA5) LRAA 28.7 ppb (11.5–35.8).

• PFAS: most recent plant‑level tests (Nov 2023) reported non‑detect for the listed compounds.
  All within regulatory limits as reported in the CCR. Nashville.gov

FRANKLIN (CITY OF FRANKLIN WATER TREATMENT + HVUD BLEND)

• Hardness: avg ~188 mg/L (Franklin plant) and ~103 mg/L (HVUD). (Hard to Moderately Hard).

• Chlorine residual: ~1.2–2.2 mg/L observed ranges.

• Fluoride: ~0.53–0.56 mg/L avg (plant/HVUD).

• DBPs (LRAA): Franklin TTHM ~39.9 ppb, HAA ~17.3 ppb; HVUD TTHM ~47 ppb, HAA ~27 ppb.

• PFAS: 2023–2024 monitoring shows no detections for listed compounds.
  Again, reported as compliant in the CCRs. City of Franklin+1

What this means for taste & use: chlorine taste/odor and hardness are the most noticeable “everyday” items; RO improves taste/odor (via carbon) and drops dissolved salts for clearer ice/coffee, while a softener/conditioner is the right whole‑home answer for glass spotting and scale on fixtures and tankless heaters. Nashville.gov

DISSOLVED SALTS & METALS (LEAD, ARSENIC, CHROMIUM, COPPER, SODIUM)

• What RO does: High rejection of many ions and metals; NSF/ANSI 58 is the baseline certification (includes TDS reduction; many models also certify specific metals). NSF

• Local tie‑in: Nashville & HVUD report sodium ~8–12 mg/L (a small amount but relevant for low‑sodium diets); lead at the tap can come from home plumbing—RO at the kitchen adds protection. Nashville.gov+2City of Franklin+2

NITRATE / NITRITE & FLUORIDE

• What RO does: Reduces nitrate/nitrite and fluoride—both listed by CDC under RO capabilities. (Always confirm your model’s performance sheet.) CDC

• Local tie‑in: Nashville & HVUD nitrate is low (<< MCL), fluoride is added (≈0.5–0.7 mg/L); RO lowers the level at your tap. If you’re mixing infant formula, follow your pediatrician’s guidance. Nashville.gov+1

PFAS (“FOREVER CHEMICALS”)

• What RO does: EPA identifies reverse osmosis among the effective home treatments for PFAS. As of 2024, consumer certifications focus on PFOA and PFOS—look for those claims on the label and replace filters on schedule. US EPA+1

• Local tie‑in: Recent CCRs for Nashville, Franklin, and HVUD show non‑detect at the plant. Many families still prefer a household barrier at the tap—RO provides that added assurance. Nashville.gov+2City of Franklin+2

MICROORGANISMS (PARASITES, BACTERIA, VIRUSES)

• What RO does: The RO membrane pore size (~0.0001 µm) is small enough to remove parasites, bacteria, and viruses when the system is designed and maintained correctly. Municipal water is already disinfected; RO adds a point‑of‑use barrier. For private wells, we can pair UV with RO. CDC

MICROPLASTICS

• What RO does: Drinking‑water treatment (including membrane processes like RO) substantially reduces microplastics; peer‑reviewed and WHO assessments support high removals. Iris+1

DISINFECTION BYPRODUCTS (DBPs: THMs & HAA5)

• Local baseline: Nashville reports TTHM ~44.8 ppb and HAA5 ~28.7 ppb (LRAA)—compliant and typical for chlorinated systems. Franklin/HVUD are similar (see above). Nashville.gov+2City of Franklin+2

• What RO + carbon do: Activated carbon stages are the primary workhorse for chlorine taste/odor and many DBPs/precursors; RO membranes add additional removal for certain low‑molecular‑weight organics. For THMs, look for NSF/ANSI 53 claims on the carbon stage. HAA5 reduction has been shown in studies, but there’s currently no widely available home‑filter certification specifically for HAA5—so check the manufacturer’s performance data before you buy. NSF+2PMC+2