How to Maintain a Tankless Water Heater

Overview

Tankless water heaters are efficient and long-lasting, but they require regular maintenance to perform at their best. Unlike traditional tank heaters, tankless units need annual flushing to remove mineral buildup that can reduce efficiency and cause damage. Proper maintenance keeps your unit running efficiently, extends its lifespan, and prevents costly repairs.

Why This Matters

Tankless water heaters can last 20+ years with proper maintenance, but mineral buildup from hard water can reduce efficiency by 20-30% and cause overheating. Regular maintenance prevents these problems, maintains energy savings, and ensures reliable hot water. The small time investment pays off in performance and longevity.

Annual Flushing and Descaling

Why Flushing is Critical

The problem:

• Mineral buildup - Hard water deposits accumulate in heat exchanger
• Reduced efficiency - Buildup insulates, reducing heat transfer
• Overheating risk - Buildup can cause unit to overheat
• Flow restriction - Reduced water flow over time

The solution:

• Annual flushing - Removes mineral deposits
• Maintains efficiency - Keeps heat transfer optimal
• Prevents damage - Avoids overheating and component failure

Flushing Process

Step 1: Turn Off Power and Water

1. Turn off power - At circuit breaker (electric) or gas supply (gas)
2. Close water valves - Inlet and outlet valves on unit
3. Wait for cooling - Let unit cool if recently used
4. Safety first - Never work on unit while powered or hot

Step 2: Connect Flushing Kit

1. Attach hoses - To service valves (usually included with unit)
2. Connect to pump - Submersible pump in bucket
3. Use descaling solution - White vinegar or manufacturer solution
4. Follow manufacturer instructions - Each unit may vary slightly

Step 3: Flush the Unit

1. Open service valves - Allow solution to circulate
2. Run pump - Circulate solution for 45-60 minutes
3. Monitor solution - Should see mineral deposits in bucket
4. Follow flow direction - Reverse flush if recommended

Step 4: Rinse and Restore

1. Flush with clean water - Remove descaling solution
2. Close service valves - Remove hoses
3. Restore water supply - Open inlet and outlet valves
4. Restore power - Turn on electricity or gas
5. Test operation - Run hot water, verify it works

Monthly Maintenance

Check and Clean Filters

Location:

• Inlet filter - Where cold water enters unit
• May be external - Easy to access
• Or internal - Requires unit access

Cleaning process:

1. Turn off water - Close inlet valve
2. Remove filter - Unscrew or pull out
3. Rinse clean - Remove debris and sediment
4. Inspect for damage - Replace if torn or damaged
5. Reinstall - Replace filter, restore water

Frequency: Monthly, or more often if you notice reduced flow.

Visual Inspection

What to check:

• Exterior condition - No damage, corrosion, or leaks
• Venting - Clear and unobstructed (gas units)
• Electrical connections - Secure, no corrosion (electric units)
• Water connections - No leaks at fittings
• Error codes - Check display for any warnings

Frequency: Monthly visual check takes just minutes.

Hard Water Considerations

More Frequent Maintenance

If you have hard water:

• Flush every 6 months - Instead of annually
• Use descaling solution - White vinegar or commercial descaler
• Consider water softener - Reduces mineral buildup
• Monitor efficiency - Watch for declining performance

Hard water signs:

• Mineral deposits - On fixtures, in appliances
• Soap doesn't lather - Hard water characteristic
• Water test - Confirm hardness level
• Scale buildup - Visible on heating elements

Professional Service

When to Call a Professional

Consider professional service if:

• Uncomfortable with process - Don't risk damage
• Complex issues - Error codes, performance problems
• Gas units - If uncomfortable with gas connections
• Warranty concerns - Some warranties require professional service
• Every 2-3 years - For comprehensive inspection

Professional service includes:

• Thorough inspection - All components checked
• Deep cleaning - More thorough than DIY
• Component testing - Verify all systems working
• Efficiency testing - Measure actual performance
• Repairs if needed - Address issues found

Cost: $150-$300 for professional tankless water heater service.

Common Issues and Solutions

Reduced Hot Water Flow

Possible causes:

• Clogged filter - Clean or replace inlet filter
• Mineral buildup - Needs descaling/flushing
• Water pressure low - Check home water pressure
• Unit undersized - For current usage

Solutions:

• Clean filter - First step
• Flush unit - Remove mineral buildup
• Check pressure - May need pressure regulator adjustment
• Consider usage - Multiple simultaneous uses may exceed capacity

Water Temperature Fluctuations

Possible causes:

• Mineral buildup - Affecting heat transfer
• Flow rate too high - Exceeding unit capacity
• Multiple fixtures - Simultaneous use
• Thermostat issues - May need adjustment or replacement

Solutions:

• Flush unit - Remove buildup
• Reduce flow - Use lower flow fixtures
• Stagger usage - Don't run multiple hot water fixtures
• Professional service - If thermostat needs adjustment

Maintenance Schedule

Annual Tasks

Once per year:

• Flush and descale - Remove mineral buildup
• Professional inspection - Every 2-3 years
• Check all connections - Water, gas, electrical
• Test safety features - Pressure relief, shut-off valves

Monthly Tasks

Every month:

• Check and clean filters - Inlet filter maintenance
• Visual inspection - Look for problems
• Check for leaks - Around connections
• Monitor performance - Water temperature, flow

Seasonal Considerations

Before winter:

• Insulate pipes - Prevent freezing
• Check venting - Ensure clear (gas units)
• Test operation - Verify working before cold weather

Cost-Benefit Analysis

Maintenance Costs

DIY maintenance:

• Flushing kit: $30-$50 (one-time)
• Descaling solution: $5-$15 per flush
• Time: 1-2 hours annually
• Total: $35-$65 per year

Professional service:

• Annual service: $150-$300
• Every 2-3 years: $300-$600

Benefits

Regular maintenance provides:

• Extended lifespan - 20+ years vs. 10-15 without maintenance
• Maintained efficiency - Keeps energy savings
• Prevents major repairs - Catches problems early
• Reliable operation - Consistent hot water

Conclusion

Regular maintenance is essential for tankless water heater performance and longevity. Annual flushing removes mineral buildup that reduces efficiency, monthly filter cleaning maintains flow, and professional service every 2-3 years ensures comprehensive care. The small time and cost investment pays off in reliable operation, energy savings, and extended lifespan. Don't skip maintenance—your tankless water heater depends on it.