Hot Water Heater Making Loud Knocking Noises? Fixes Here

If your hot water heater has started making loud banging or knocking noises, it can be an alarming and disruptive issue. That rhythmic knocking sound is more than just annoying - it could signal real problems with your hot water heater that need attention.

With some basic maintenance and repairs, you can stop that racket and keep your hot water heater running more efficiently.

What's Causing the Knocking Noise?

Before jumping into solutions, it's important to understand what's causing the knocking or banging noise in the first place. There are a few key culprits:

• Sediment Buildup - Over years of operation, minerals from your water supply gradually form sediment at the bottom of the tank. As the sediment accumulates, it eventually expands and contracts when heated and cooled, making the knocking or popping noise.
• Corrosion - Corrosion of internal components like water pipes and fittings causes weak points that can rattle or bang as heated water flows through them. This is more common with older tanks.
• Loose Parts - If any internal water pipes, inlet/outlet fittings or other components have become loose inside the tank, they can rattle around when hot water runs through them.
• Water Hammering - When high water pressure slams the heat elements or pipes, it creates a knocking or banging water hammering noise. This usually happens when a faucet or valve shuts abruptly.
• Defective Thermostat - If the thermostat fails and doesn't properly turn the heating elements on and off, the water can overheat. This boiling action leads to knocking and banging noises.
• Cracked Heat Exchanger - In tankless water heaters, cracks in the heat exchanger can cause clicking or tapping sounds as pressurized water passes through the damaged area.

How to Pinpoint the Source

To choose the right fix, you first need to diagnose the specific cause. Follow these troubleshooting steps:

• Listen Closely - Note exactly where the knocking is coming from - the bottom, side, internal pipes, etc.
• Consider When It Happens - Only occurs when heating water? Or persistent knocking?
• Account for Age - Old tanks over 8-10 years are more prone to sediment and corrosion.
• Check Water Pressure - Using a gauge, ensure your home's water pressure is in the 50-60 PSI range.
• Look for Leaks or Drips - Signs of water leaks point to corrosion and rust inside the tank.
• Remove outer cover - Open the outer metal jacket to expose insulation and listen for specific locations of noise.
• Check for loose valves or fittings - Give pipes and fittings a gentle nudge to see if any are loose and rattling.

Temporary Fixes to Stop the Noise

Before taking more intensive repair steps, try these simple DIY fixes to silence knocking noises from your water heater:

• Drain Some Water - This reduces the internal pressure and may stop water hammering noises.
• Secure Loose Pipes or Parts - If you detected rattling from a loose fitting or pipe, tighten it to prevent vibration.
• Lower Temperature Setting - Excessively hot water causes boiling. Lower the thermostat to 120-140 degrees.
• Quick Flush - Flushing the tank may dislodge sediment accumulation and mineral buildup causing noises.
• Raise Temperature Setting - If knocking only happens with cool water, slightly increase the temp setting.
• Update Plumbing - Inspect water supply lines and update to flexible braided steel lines to absorb vibrations.

Calling in a Professional

DIY repairs may solve the problem, but it's wise to call a professional hot water heater repair technician if:

• Knocking Persists - The noise continues regularly after your troubleshooting attempts.
• Significant Leaks - You notice large leaks pointing to internal corrosion.
• Unit Over 10 Years Old - Past this age, repairs are often needed and replacement should be considered.
• Unsure of Cause - You've tried diagnosing it yourself but can't pinpoint the exact issue.

A pro has specialized tools and expertise to fully diagnose the problem. They can also determine if repairs are needed or a complete replacement is your best option.

In-Depth Repairs and Replacement

For a permanent solution to knocking noises, significant repairs or full replacement may be necessary:

• Replace Thermostat - If it's failing to maintain the proper water temperature, replace it to prevent overheating.
• Install Pressure Regulator - For water hammering noises, this device maintains safe water pressure levels entering your home.
• Thorough Flushing Service - Removes accumulated sediment clogging the tank bottom. This often requires a professional to perform correctly.
• Replace Anode Rod - Corroded rods cause scale buildup. Swap it out for an epoxy-coated aluminum anode rod.
• Repair/Replace Heat Exchanger - For tankless heaters, a cracked exchanger needs professional repair or replacement.
• Install Expansion Tank - This provides space for water thermal expansion and prevents water hammering.
• Full System Replacement - For older tanks with severe corrosion and sediment buildup, full replacement is likely the best solution.

Preventive Maintenance

With annual maintenance, you can minimize sediment buildup and corrosion that lead to knocking noises:

• Yearly Flushing - Drain and flush the tank to prevent sediment accumulation.
• Annual Anode Inspection - Check the anode rod and replace if corroded.
• Monitor Water Pressure - Use a pressure reducing valve to keep home water pressure under 60 PSI.
• Update Connections - Replace worn washers and ensure fittings are tight.
• Check for Air Pockets - Air trapped in plumbing lines can lead to knocking. Bleed the lines to remove it.

When Full Replacement is Needed

Even with repairs, an old and deteriorated hot water heater will usually need full replacement. Signs it's time to replace the unit:

• - Leaks from multiple locations on the tank.
• - Heavily corroded internal components.
• - Visible holes from rust and corrosion on the outer tank.
• - Sediment layer exceeds 6 inches thick.
• - Heating elements repeatedly burning out.
• - Thermostat completely fails and no longer functions.
• - Energy efficiency less than 50% per the EF rating.

Choosing a New Water Heater

Selecting a suitable replacement unit involves a few key considerations:

• Fuel Type - Gas heaters heat water faster. Electric models can supplement solar power systems.
• Tank vs Tankless - Tankless provides unlimited hot water but installation costs are higher.
• Capacity - Right-size the tank capacity and heating element wattage for your home.
• Efficiency Rating - Look for the Energy Factor (EF) rating. 0.95+ is highly efficient.
• Warranty - Choose a model with at least a 6 year warranty on the tank.
• Professional Installation - Have a licensed plumber install it to meet codes and reduce risks.

Annoying knocking or banging coming from your hot water heater should be addressed promptly. DIY troubleshooting and repairs can often resolve the issue. But if noises persist after trying fixes, bring in a professional to thoroughly inspect and service the unit. For older tanks with severe damage, a full replacement is the permanent solution. With regular maintenance and replacing degraded heaters, you can prevent disruptive knocking noises and enjoy reliable hot water delivery.