Water Filtration Technologies Reference
Overview
Multiple filtration technologies handle different contaminants. Matching the technology to the problem is the key skill.
Sediment filters
What they remove:
- Sand, silt, rust particles, debris
- Sized by micron rating (5 μm, 20 μm, 50 μm, etc.)
Types:
- Pleated filter cartridges (reusable; wash + reuse)
- Spun polypropylene (disposable; common)
- String-wound (better dirt-holding capacity)
- Bag filters (high-flow commercial)
Typical placement: First in line (whole-house)
Service life: 3-12 months depending on water
Activated carbon
What it removes:
- Chlorine + chloramines (taste + smell)
- Organic compounds (VOCs)
- Pesticides (some)
- Color (sometimes)
Types:
- Granular activated carbon (GAC): packed in tank or cartridge
- Carbon block: solid carbon mass; higher contact time
- Catalytic carbon: enhanced for chloramine removal
Important: doesn't remove most dissolved minerals, hardness, bacteria.
Typical placement: After sediment, sometimes after softener
Service life: 6-24 months (depends on chlorine + contaminant levels)
Reverse osmosis (RO)
What it removes:
- 95-99% of dissolved solids
- Sodium (yes, including post-softener sodium)
- Lead, arsenic, fluoride, nitrate
- Bacteria (some - not all)
- Almost everything
Wastes water: 3-4 gallons of reject water per gallon produced
Typical placement: Point-of-use (kitchen tap)
Service life: Membrane 2-3 years; pre/post filters 6-12 months
Distillation
What it removes:
- Almost everything (boil + condense)
- Very pure water
Pros:
- Highest purity
- No chemicals
Cons:
- Slow (gallons per day)
- Energy-intensive
- Tastes "flat" (most minerals removed)
Typical use: Lab applications; some medical home use
Ultraviolet (UV) disinfection
What it removes:
- Kills bacteria, viruses, protozoa
- Does NOT remove particles or chemicals
Requirements:
- Clear water (turbidity blocks UV)
- Adequate dwell time
- 12-month lamp replacement (degrades over time)
Typical placement: Last stage before delivery (whole-house or POU)
Service life: UV lamp 12 months
Ion exchange (softener)
What it removes:
- Calcium + magnesium (hardness)
- Some iron (low levels)
Adds:
- Sodium to water (small amount)
Wastes water: 30-80 gallons per regeneration
Typical placement: Whole-house, after iron filter (if iron present)
Service life: Resin 10-15 years
Anion exchange
What it removes:
- Nitrates
- Sulfates
- Some other anions
Specialty use: When testing reveals high nitrates from agricultural runoff.
Iron filters
What they remove:
- Iron + manganese
Types:
- Air-charged (oxidizes + filters): manganese dioxide media
- Greensand (manganese + iron filter)
- Birm (catalytic oxidation)
Service life: Media 5-10 years; regeneration salt or potassium permanganate
Sulfur removal
What they remove:
- Hydrogen sulfide (rotten egg smell)
Methods:
- Aeration + carbon
- Chlorine injection + carbon
- Specialty media (manganese dioxide)
Maintenance: Chemicals + media replacement
Acid neutralization
What they remove:
- Acidic conditions (raises pH)
Methods:
- Calcite (natural limestone): self-replenishing; gradually depletes
- Soda ash injection: chemical addition
Service life: Calcite 5-10 years
UV + RO hybrid
For ultimate residential water:
- Pre-filter (sediment)
- RO (removes 99%)
- UV (kills any survivors)
- Point-of-use only typically
Water Softener vs Salt-Free "Conditioner"
Traditional softener (ion exchange):
- Removes hardness
- Adds sodium
- Lab-tested + proven
Salt-free "conditioner" (template-assisted crystallization):
- Doesn't remove hardness (just transforms it)
- Hardness still measures the same
- Less lather; soap scum still possible
- No salt usage (advantage)
- Doesn't help with appliance scale fully
Recommend salt-free only for:
- Sodium-restricted diet customers
- Customers willing to accept some compromise
- Combine with POU RO for drinking
Specialty technologies
Electrodeionization (EDI):
- High-purity; commercial/industrial
- No chemicals
- Continuous deionization
Catalytic carbon:
- Specifically removes chloramines
- More expensive than standard carbon
Greensand filter:
- Iron + manganese
- Regenerated with potassium permanganate
Filter cartridge sizes (standard):
- 10" × 2.5" (most common residential)
- 10" × 4.5" (whole-house typical)
- 20" × 2.5" or 4.5" (larger applications)
Decision matrix
Customer concern → Recommended technology:
| Concern | Treatment |
|---|---|
| Hardness only | Softener |
| Hard + iron | Iron filter + softener |
| Hard + chlorine taste | Softener + carbon |
| Drinking water quality | POU RO |
| Bacteria (well water) | UV |
| Acidic water | Calcite neutralizer |
| Sulfur smell | Aeration + carbon or chlorine + carbon |
| Heavy contamination | Multi-stage system |
Cost summary by technology
| Technology | Whole-house cost |
|---|---|
| Sediment filter | Lowest of the group |
| Activated carbon | A meaningful step up from sediment |
| Softener | Roughly comparable to carbon at the low end, running several times higher at the top end |
| Iron filter | Comparable to a mid-range softener |
| UV system | Similar range to an iron filter |
| Acid neutralizer | Comparable to activated carbon |
| Full multi-stage system | The most expensive by far, several times any single technology on this list |
Service lifecycle
Most filtration components require periodic maintenance:
- Sediment: replace 3-12 months
- Carbon: replace 6-24 months
- Softener salt: weekly to monthly refill
- UV lamp: replace 12 months
- Membrane (RO): replace 2-3 years
- Resin (softener): replace 10-15 years
Service contracts: a modest annual fee for full residential.
The single biggest filtration misconception: ASSUMING ONE TECHNOLOGY HANDLES EVERYTHING. Customer wants "filtered water" + thinks one filter does it all. Reality: hard water needs softener; chlorine needs carbon; bacteria needs UV; lead needs RO. Each contaminant has its right tool. Design a TRAIN of stages, not a single filter.
References
- WQA technology standards
- NSF 42, 53, 58, 60 (certification)
- Manuall internal: Water Chemistry Basics, Reverse Osmosis System Installation SOP