Stop the Drip! Uncovering the Mysteries Behind Tankless Water Heaters Dripping From the Bottom

Tankless water heaters have significantly changed how homeowners obtain hot water, boasting many benefits such as energy efficiency, compact designs for all family sizes, and a continuous hot water supply. However, despite these advantages, these heaters can still encounter issues throughout their lifespan. One prevalent problem is the tankless water heater dripping from the bottom.

It is essential to address these concerns promptly to prevent additional damage to the water heater and ensure optimal performance. This article seeks to illuminate the common causes behind this dripping. In addition, we’ve offered practical solutions to help you resolve the issue swiftly and effectively.


Condensation is a natural process in which water vapor cools and transforms into liquid droplets. In tankless water heaters, condensation occurs when cold water enters the unit and undergoes rapid heating. Steam is generated as the water temperature increases, which cools and condenses into water droplets. While this process is typical, certain conditions may result in excessive condensation within the heater. The excessive condensation is what leads to water dripping from the bottom of the unit.

Causes of excessive condensation

Two main causes of excessive condensation could lead to your tankless water heater dripping from the bottom. These are:

– Improper exhaust system

– Cold surrounding air temperature

Improper exhaust system

An improperly functioning exhaust system is one of the primary causes of excessive condensation in tankless water heaters. If the exhaust system fails to vent the steam generated during the heating process efficiently, condensation can accumulate within the unit and eventually lead to dripping.

Cold surrounding air temperature.

Another contributing factor to excessive condensation is the low air temperature surrounding the heater. When the heater is installed in a cold environment, the temperature difference between the incoming water and the ambient air can exacerbate condensation.

Solutions to fix condensation issues

Luckily, there are two solutions to condensation causing your tankless water heater to drip from the bottom. These are:

– Address any exhaust system issues

– Insulate the installation area

Address Exhaust System Issues

To tackle condensation problems, begin by ensuring the exhaust system functions correctly. Examine the venting system for any blockages or obstructions and clean them as necessary. Additionally, consider having a professional inspect the exhaust system to confirm its proper installation.

Insulate the Installation Area

If your tankless water heater is installed in a cold environment, consider insulating the space to maintain a more stable temperature. Insulation can help mitigate condensation by reducing temperature variations and eliminating cold air drafts. Moreover, adequate insulation can enhance the overall efficiency of your tankless water heater, resulting in energy savings over time.

Loose Connections

Water inlets and outlets to a white tankless water heater
Connections to a tankless water heater may cause dripping from the bottom if they are loosely fitted.

Loose connections within a tankless water heater can result in dripping or leakage. Water may escape through the gaps of these connections and flow out of the unit. Over time, these connections can loosen, which can compromise the efficiency and performance of the heater.

Types of connections to check

Two primary types of connections warrant close attention when inspecting a tankless water heater for loose connections. First, the water inlet and outlet connections, where cold water enters the heater, and hot water exits the unit, are susceptible to loosening over time and can cause dripping from the bottom of the heater.

Second, the internal component connections, which include various connections between components such as pipes, valves, and fittings, can also become loose and lead to internal water leaks that eventually result in dripping. Regularly checking these connections and promptly addressing any issues will ensure optimal performance and longevity of the tankless water heater.

Water Inlet and Outlet Connections

The water inlet and outlet connections are where cold water enters the heater, and hot water exits the unit. These connections are prone to loosening over time, causing water to drip from the bottom of the heater.

Internal Component Connections

Inside the tankless water heater, various connections exist between components, such as the flow control valve, mixing valve or the pressure relief valve. In addition, the connections between optional features such as recirculation pump valves and drain valves can cause dripping due to loosening over time. If any of these connections become loose, they can cause water to leak internally, eventually dripping from the bottom of the unit.

Solutions to fix loose connections

Effectively addressing loose connections in a tankless water heater involves turning off the power and water supply to the unit, followed by a thorough inspection of both the water inlet and outlet connections and the internal component connections.

In cases where damaged or worn parts are discovered, such as cracked pipes or worn-out seals, prompt replacement with manufacturer-approved parts is essential. Enlisting the help of a professional plumber is a wise decision when the repairs demand specialized expertise.

Inspect and tighten connections.

To resolve the issue of loose connections, start by turning off the power and water supply to the heater. Then, carefully inspect the water inlet, outlet, and internal component connections. If you find any loose connections, use a wrench to tighten them securely. Be careful not to over tighten, which can damage the fittings or components.

However, it might be a good idea to install the optional isolation valves which allow maintenance without needing to turn your tankless water heater off.


Damaged or Worn Components

Damaged or worn components within a tankless water heater can contribute to dripping from the bottom of the unit. Over time, various parts may deteriorate due to normal wear and tear, exposure to heat and pressure, or even poor water quality. When components become damaged or worn, they may fail to perform their intended functions, leading to internal leakage that eventually manifests as dripping.

Common damaged or worn components

Typical damaged or worn components within a tankless water heater include the heat exchanger, and valve seals that ensure the watertight integrity of the system. This step goes hand in hand with checking for loose connections, as wear and tear can cause leaking too.

Such wear and tear on these components compromises their ability to perform their intended functions and leading to internal leakage or other performance issues. Regular inspections and maintenance can help identify and address these vulnerabilities, ensuring the continued efficiency and longevity of the tankless water heater.

Heat exchanger

The heat exchanger is a crucial component of a tankless water heater, responsible for transferring heat from the burner or heating element to the water. Unfortunately, the heat exchanger can become corroded or develop cracks over time due to constant exposure to heat, pressure, and minerals in the water. These defects can cause water to leak internally and drip from the bottom of the unit.

Valves and Seals

Valves and seals are essential for maintaining the watertight integrity of a tankless water heater. Essential seals within a tankless water heater include gaskets and O-rings, which are both made from rubber or silicone. However, these components can wear out or become damaged with time and use, leading to water leakage within the unit.

Solutions to fix damaged or worn components

Addressing damaged or worn components in a tankless water heater necessitates a proactive approach, which includes conducting regular inspections to identify compromised parts, such as cracked heat exchangers or leaking valves. Timely replacing these components using manufacturer-approved parts ensures proper fit and functionality, maintaining the system’s integrity. 

In addition, planning yearly maintenance routines prolongs the heater’s lifespan and minimizes the risk of leaks and other issues. In cases where repairs demand specialized expertise, consulting a professional plumber is the best course of action.

Inspect and replace damaged parts.

If you suspect that damaged or worn components are the source of dripping from the bottom of your tankless water heater, conduct a thorough inspection of the unit for any signs of damage, such as a cracked heat exchanger, leaking valve, cracked pipes, or worn-out seals.

Upon identifying compromised components, it is imperative to replace them in a timely manner to prevent decreased efficiency and potential damage to other parts. Utilize manufacturer-approved parts for replacements to guarantee appropriate fit, functionality, and compatibility. If you are unsure about performing these repairs, consult a professional plumber.

Regular maintenance and inspections

It is vital to conduct routine maintenance and inspections to safeguard your tankless water heater’s components from damage and mitigate the probability of dripping. Such preventative measures encompass system flushing to eliminate sediment and scale accumulation, assessing valves and seals for wear, and confirming the heat exchanger’s optimal condition. 

Diligent maintenance of your tankless water heater prolongs its service life and reduces the potential for leaks and other complications. The period between inspections depends on your model and location. Once a year should be sufficient but if you live in an area with hard water, which can lead to mineral buildup and scaling inside the heat exchanger, consider checking it every six months.

Improper Installation

The inner workings of a tankless water heater
Improper installation may cause water to drip from the bottom of your tankless water heater.

Various problems can stem from the improper installation of a tankless water heater, including dripping from the bottom of the unit. This is often caused when the heater is not installed according to the manufacturer’s guidelines.

Common installation mistakes

Common installation mistakes can significantly impact the performance and longevity of a tankless water heater. These errors may include:

  • Improper pipe sizing, which can create pressure imbalances and restrict water flow, incorrect venting may lead to condensation buildup and suboptimal combustion.
  • Inadequate clearances around the heater, a potential safety hazard. Ensuring adherence to manufacturer guidelines and local building codes during installation can help mitigate these issues.

Incorrect pipe sizing

Utilizing the wrong pipe size during the installation can result in pressure imbalances and impeded water flow. This can place undue stress on the unit’s components, potentially leading to leaks. Furthermore, improper pipe sizing can adversely impact the overall efficiency and performance of the heater. 

Insufficient venting

Appropriate venting is paramount for a tankless water heater’s safe and efficient functioning. Inadequate venting may result in the accumulation of condensation within the unit, leading to water leakage and dripping from the heater’s bottom. Thus, ensuring proper venting following manufacturer guidelines is crucial for optimal performance and preventing potential issues.

Solutions to fix improper installation

To fix installation issues, it is crucial to consult a professional plumber or technician for an assessment of the unit. These experts can identify and correct installation errors. These errors include incorrect pipe sizing, improper venting, or insufficient clearances, ensuring the heater operates safely and efficiently. In addition, adhering to manufacturer guidelines and local building codes during the reinstallation process can help prevent recurring issues.

Consult a professional for reinstallation

If you think the dripping issue in your tankless water heater stems from improper installation, it’s always best to get a professional plumber or technician in for an assessment. These professionals can pinpoint installation errors and proceed with the correct reinstallation of the unit, guaranteeing safe and efficient operation. Endeavouring to rectify installation issues independently can be hazardous and potentially invalidate the manufacturer’s warranty.

Follow manufacturer guidelines

To avert installation-related complications with your tankless water heater, it is imperative to adhere to the manufacturer’s installation guidelines and local building codes and regulations. This encompasses selecting suitable pipe and vent sizes, securely mounting the unit, and preserving sufficient clearances around the heater. By observing these directives, you can mitigate the likelihood of leaks, enhance the efficiency and performance of your heater, and extend its service life.

Final Thoughts 

We’ve delved into the causes of dripping from the bottom of a tankless water heater. This includes condensation, loose connections, damaged or worn components, and improper installation. Moreover, we have explored a range of solutions to these issues, including inspections, repairs, securing connections, and using a professional.

Consistent maintenance and inspections play a vital role in averting and detecting potential concerns with your tankless water heater. Adopting a proactive approach and adhering to the manufacturer’s recommended maintenance schedule can ensure the efficient operation of your heater. In addition, it extends its service life and reduces the risk of leaks and other complications.

While dripping from the bottom of a tankless water heater might initially appear to be a minor issue, it is crucial to address it right away. This prevents exacerbating damage to the unit and preserves its peak performance. By pinpointing the underlying cause of the dripping and applying suitable solutions, you can safeguard your investment and relish the advantages of an efficient, dependable tankless water heater.

With a background in architecture, journalism, and content writing, I craft my knowledge and extensive research into readable and educational tankless water heater articles that anyone can follow.