RO Terms: TDS, GPD & Recovery Ratio - What Actually Matters for Water Purifiers
Decode essential RO water purifier terminology: TDS levels, GPD ratings, and recovery ratios. Understand what these specs mean for real-world performance and how to choose the right water purifier.
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Technical Guide
Technical explanation
💧 RO Terms Decoded: TDS, GPD & Recovery Ratio
What You'll Learn
Cut through confusing RO water purifier jargon. Understand what TDS, GPD, and Recovery Ratio actually mean, how they affect your daily water usage, and which specs matter most when buying a water purifier.
💡 Quick Summary
📊 TDS
Total Dissolved Solids. Indian water: 100-400 ppm municipal, higher in borewells.
💦 GPD
Gallons Per Day - lab flow rating. Real output drops with cold water/low pressure.
♻️ Recovery
Clean water percentage. Typical RO: 25-50% efficiency, rest becomes wastewater.
📊 1. TDS (Total Dissolved Solids) - The Water Quality Indicator
What TDS Really Means
Total concentration of dissolved substances in water, measured in parts per million (ppm) or milligrams per liter (mg/L)
🌊 Understanding TDS Levels
TDS Range Classification
Indian Water Source TDS
🧪 What's Actually in High TDS Water?
Common Dissolved Substances
🧂 Beneficial Minerals
- • Calcium: Bone health, taste enhancement
- • Magnesium: Essential mineral, muscle function
- • Potassium: Heart health, electrolyte balance
- • Sodium: Electrolyte (in moderate amounts)
⚠️ Harmful Contaminants
- • Lead: Neurological damage
- • Arsenic: Cancer risk, organ damage
- • Fluoride: Dental/skeletal fluorosis (excess)
- • Heavy metals: Various health issues
💦 2. GPD (Gallons Per Day) - Flow Rate Reality Check
What GPD Actually Measures
Theoretical maximum water production under ideal laboratory conditions - not your real-world experience
🏭 Lab Conditions vs Reality
Ideal Lab Conditions
Real Home Conditions
📉 Real-World Output Factors
What Reduces GPD Output
Practical GPD Expectations
🏠 Sizing GPD for Your Family
| Family Size | Daily Need (L) | Minimum GPD | Recommended GPD |
|---|---|---|---|
| 2-3 people | 10-15 L | 50 GPD | 75 GPD |
| 4-5 people | 20-25 L | 75 GPD | 100 GPD |
| 6+ people | 30+ L | 100 GPD | 150+ GPD |
♻️ 3. Recovery Ratio - The Water Waste Reality
What Recovery Ratio Means
Percentage of input water that becomes clean drinking water - the rest becomes wastewater
💧 Understanding Recovery Efficiency
Typical Recovery Ratios
Factors Affecting Recovery
💰 Water Waste Cost Impact
Monthly Water Consumption Analysis
25% Recovery System
- • 20L clean water daily need
- • 60L wastewater produced daily
- • Total input: 80L daily (2,400L monthly)
- • Extra cost: ₹180-300/month in water bills
50% Recovery System
- • 20L clean water daily need
- • 20L wastewater produced daily
- • Total input: 40L daily (1,200L monthly)
- • Savings: ₹90-180/month vs 25% system
♻️ Wastewater Reuse Ideas
Direct Use Applications
Collection & Storage Tips
🎯 4. What Actually Matters When Buying
Priority Order for Spec Evaluation
Focus on specs that actually impact your daily water usage experience
🥇 Priority 1: Input TDS Testing
Why TDS Testing Comes First
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✓
Determines Need: Low TDS areas may not need RO
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✓
System Sizing: High TDS needs more capacity
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✓
Performance Prediction: Affects GPD and recovery
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✓
Maintenance Planning: Higher TDS = more frequent service
Testing Your Water
🥈 Priority 2: Recovery Ratio Evaluation
Why Recovery Matters Most
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💰
Operating Cost: Directly affects monthly water bills
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🌍
Environmental Impact: Less water waste
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🏠
Tank Filling: Faster clean water production
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♻️
Reuse Opportunities: Less wastewater to manage
🥉 Priority 3: Realistic GPD Assessment
GPD Reality Check Formula
Derating Factors
- • Temperature: -10 to -20%
- • Pressure: -15 to -30%
- • High TDS: -10 to -25%
- • Membrane age: -10 to -15%
Size Accordingly
- • Always oversize by 25-50%
- • Consider peak usage periods
- • Plan for membrane degradation
- • Factor in storage tank capacity
🚫 Common Spec Misconceptions
Myth
"Lower TDS output water is always healthier"
Reality
50-150 ppm TDS is ideal - maintains beneficial minerals while removing harmful contaminants. Ultra-low TDS may lack essential minerals.
Myth
"Higher GPD rating means faster water"
Reality
GPD is daily capacity, not flow rate. A 75 GPD system produces ~3L/hour under ideal conditions, often less in real use. Storage tank size affects perceived speed more than GPD rating.
❓ Frequently Asked Questions
Quick Answers
Common questions about RO water purifier specifications and performance
Q: What TDS level should I target for my family's drinking water?
A:
Aim for 50-150 ppm TDS in your output water. This range provides beneficial minerals while ensuring safety. If your input water is below 300 ppm and tastes good, you might not need RO - consider UV or UF purification instead.
Q: Why is my RO system producing much less water than the GPD rating?
A:
This is normal. GPD ratings are for ideal lab conditions (25°C, 60 PSI, new membrane). Real output is typically 60-80% of rated capacity due to temperature, pressure, TDS levels, and membrane age. Always size systems 25-50% higher than your calculated need.
Q: Is the wastewater from RO systems really safe to reuse?
A:
Yes, for many applications. RO wastewater typically has 2-3x the TDS of input water but is free from bacteria and most contaminants. It's safe for toilet flushing, floor cleaning, gardening (check plant salt tolerance), and car washing. Use within 24-48 hours to prevent bacterial growth.
Q: How can I improve my RO system's recovery ratio?
A:
Install a pressure booster pump if your water pressure is below 40 PSI, ensure regular membrane replacement, adjust the waste water flow valve (if adjustable), and consider systems with built-in recirculation. However, don't compromise water quality for higher recovery - maintain proper rejection ratios.
Q: Should I buy the highest GPD system available for my home?
A:
Not necessarily. Higher GPD systems cost more and may have lower recovery ratios. Calculate your actual daily need (3-4L per person), add 25-50% buffer, and choose accordingly. A 75 GPD system is sufficient for most 4-person families. Focus more on recovery ratio and build quality than maximum GPD rating.
🎯 Key Takeaways
This article explains the key concepts behind water purifier-specs in simple terms for water purifier buyers.