Vented Hot Water Cylinders: A Beginner’s Guide

vented hot water cylinders a beginners guide

Whether you’re maintaining an existing vented system or contemplating a switch, we have put together a beginner’s guide of what you need to know about vented hot water cylinders. This guide provides insights to make informed decisions about your hot water system.

Within older households, a vented hot water cylinder is an essential component in traditional hot water systems. They are often found in terrace houses, semi-detached and older detached homes, along with builds from the Victorian and Edwardian eras. Vented hot water cylinders are considered to be a traditional option, compared to unvented cylinders.

Definition and Basic Operation of Vented Hot Water Cylinders

Their primary purpose is to store and supply hot water for domestic use, such as bathing, cleaning, and cooking. These systems utilise the natural rise of hot water, working on a gravity-fed system.

Cold water enters the cylinder from the mains and is heated by an external heat source, such as a boiler or immersion heater. The water then rises to the top of the cylinder, where it is drawn off to be used for domestic purposes.

Importance of Proper Ventilation

As you can expect, adequate airflow around the cylinder helps prevent the tank from overheating. Furthermore, it optimises its performance, minimises the risk of corrosion, and maintains the efficiency and longevity of the vented hot water system.

Pros and Cons of Vented Cylinders

Vented cylinders have their advantages and potential drawbacks. From cost-effectiveness to considerations about pressure and space, weighing these factors can guide you in making an informed decision tailored to your specific needs and preferences.


  • Cost-Effective: Vented hot water cylinders are often more affordable to install. This is due to their simple design, as well as often already being part of a household’s hot water system.
  • Compatibility with Renewable Energy Sources: Vented systems can be easily integrated with renewable energy sources, such as solar thermal panels. This makes them a more sustainable option for homeowners seeking to reduce their carbon footprint.
  • Longevity: Through simple and regular maintenance, such as checking for leaks, corrosion, and sediment buildup, as well as their straightforward functionality, a vented hot water cylinder can have a long operational life.
  • Energy Efficiency with Thermostatic Control: A built-in thermostat helps maintain water temperature at desired levels. This precise control promotes energy efficiency by preventing unnecessary heating, ultimately reducing energy consumption.
  • Backup Immersion Heater: The inclusion of an immersion heater in vented cylinders provides a reliable backup heating option. This ensures a continuous supply of hot water even if the main heat source is temporarily unavailable.


  • Limited Water Pressure: Vented systems often provide lower water compared to pressurised (unvented) systems.
  • Space Requirements: With the need for a cold water header (feed & expansion) tank, alongside the vented hot water cylinder, a significant amount of space is required.
    However, SlimFit or Combi cylinders could be a solution for this issue. The latter is ideal for smaller homes.
  • Energy Inefficiency: While vented systems are commonly efficient, they may experience heat loss due to the need for a vent pipe. Insufficient insulation can contribute to energy inefficiency, especially in older installations.
  • Maintenance of Vent Pipe: The vent pipe requires regular maintenance to ensure proper functioning. Accumulation of debris or blockages can affect the performance of the entire vented hot water system.
Vented Heap Pump Cylinder (Newak Cylinders)
An example of Newark Cylinders’ Vented Heat Pump Cylinder model.

Installation Tips


Due to being part of an unpressured water system, it is advised to install a vented hot water cylinder close to points where there is a demand for hot water. Having a vented cylinder near a bathroom or kitchen reduces the distance water needs to travel, enhancing efficiency in the process.

Additionally, it will also be convenient when you need to maintain and inspect the vented cylinder.

It is advised that professional installation is part of the process to ensure compliance with regulations.


As previously mentioned, having proper airflow dissipates excess heat from the cylinder, preventing it from overheating. Excess heat can especially develop when an immersion heater is used.

Additionally, good ventilation minimizes the risk of corrosion, as stagnant, humid air around the cylinder can contribute to metal degradation over time.

Although some methods of maintaining your vented hot water cylinder can be done at home, it is advised to seek out the help of a professional for tasks such as sediment flushing.
Image by Freepik.


Ensuring the longevity and optimal performance of your vented hot water cylinder requires routine maintenance. By following these guidelines, you can address common issues, prevent potential problems, and keep your hot water system operating efficiently.

Regular Inspection

Conducting regular checks for leaks, corrosion, or any other visible wear. Checking the surrounding area for dampness can be an indication of a potential issue.

Additionally, inspecting the insulation for any signs of wear, damage, or gaps is advised. Furthermore, insulating any exposed pipes connected to the cylinder is worth considering to further reduce heat loss.

Sediment Flushing

Over time sediment (dissolved minerals) can build up in the vented cylinder. This is due to the heating of water and condensed minerals settling in the bottom of the tank. Sediment accumulation can affect water quality and reduce the cylinder’s efficiency.

To prevent excess build-up of sediment, it is advised to have your hot water cylinder drained and flushed yearly. However, it is advised that a certified plumber handle this type of maintenance.

Anode Rod Checks and Replacement

An anode rod is considered one of the most important elements inside of a water heater. The anode rod attracts and absorbs harmful particles, such as sediment buildup, to its surface. In short, it protects the cylinder from rust.

Regularly inspecting the anode rod is advisable. If the rod shows signs of significant deterioration or is less than half its original size, consider replacing it. Anode rod replacement can extend the life of the cylinder and ensure it continues to function effectively.

Temperature and Pressure (TPR) Valve Testing

Regularly testing the temperature and pressure relief valve (TPR valve) will ensure it functions correctly. This can be done by lifting the valve’s lever partway to allow a small amount of water to be discharged. This helps verify that the valve opens and closes smoothly.

 If the valve doesn’t operate properly, or water continues to discharge, it may indicate a problem with pressure or temperature within the cylinder.

In such cases, consult a professional for further assessment and potential valve replacement.

Considerations for Switching to Vented Systems

If you are considering switching to a vented hot water system, there are numerous factors to think about.

Existing Infrastructure

Evaluate the compatibility of a vented hot water system. Your household may need modifications for a vented system to be installed, especially when transitioning from a pressurised system.

On a related note, assessing your water pressure needs is ideal. Vented systems are gravity-fed and require a water pump to provide high-pressure water.

Space Availability

Similar to evaluating a building’s infrastructure, a vented system requires sufficient space for a cold water header tank, and vented hot water cylinder to be installed.

Energy Efficiency Considerations

Comparing the energy efficiency of vented systems with other available options can be beneficial. When doing this, it’s important to consider factors such as insulation, heat loss, and the impact on utility bills.

Professional Consultation

Seeking advice from plumbing and heating professionals is strongly advised. Consulting with experts can provide valuable insights into the feasibility and practicality of switching to a vented hot water system based on your specific circumstances and requirements.


In conclusion, understanding the intricacies of vented hot water cylinders enables homeowners to make knowledgeable choices concerning their heating systems.

As you maintain an existing vented system or contemplate a switch, regular inspections and adherence to maintenance guidelines are essential for ensuring longevity and optimal performance.

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