Unvented Water Heaters

5 products

  • Dexpro Unvented water heater

    Dexpro Delux Digital Unvented Water Heater 10 Litres

    Dexpro Delux Digital Unvented Water Heater 10 Litres

    £81.00 GBP
    £81.00 GBP
  • Dexpro Unvented water heater

    Dexpro Delux Digital Unvented Water Heater 15 Litres

    Dexpro Delux Digital Unvented Water Heater 15 Litres

    £90.00 GBP
    £90.00 GBP
  • Dexpro Unvented water heater

    Dexpro Delux Digital Unvented Water Heater 6 Litres

    Dexpro Delux Digital Unvented Water Heater 6 Litres

    £78.00 GBP
    £78.00 GBP
  • DexPro Delux Stainless Steel Unvented Water Heater

    DexPro Delux Stainless Steel Unvented Water Heater

    DexPro Delux Stainless Steel Unvented Water Heater

    £90.00 GBP
    £118.80 GBP -25%
    £90.00 GBP
    £118.80 GBP
  • Zip Aquapoint Unvented Water Heater

    Zip Aquapoint Unvented Oversink/Undersink Water Heater

    Zip Aquapoint Unvented Oversink/Undersink Water Heater

    From £209.62 GBP
    £359.35 GBP -42%
    From £209.62 GBP
    £359.35 GBP

Unvented water heaters, also known as unvented hot water cylinders, are a modern alternative to traditional vented systems. The key distinction is that they are sealed units that draw cold water directly from the mains supply, rather than relying on a separate cold water storage tank in the loft. This direct connection to the mains water pressure is the source of their primary benefits.

The categories of unvented water heaters are primarily defined by their heating method and physical design.

1. Direct Unvented Water Heaters

These cylinders heat the water internally using electric immersion heaters. They are a self-contained system for producing hot water, making them suitable for properties where a boiler or other external heat source is not available or desired.

  • Key Features:
    • Internal Heating: Equipped with one or more electric immersion heaters. Some models have two—a primary one at the bottom for off-peak economy tariffs (like Economy 7) and a "boost" heater midway up for quick hot water on demand.
    • Simplicity: The setup is relatively straightforward, as it doesn't require a connection to a central heating boiler.
    • Application: Ideal for small-to-medium-sized homes, apartments, or commercial properties that do not have a central heating system or as a backup hot water source.

2. Indirect Unvented Water Heaters

These units rely on an external heat source to heat the water inside the cylinder. The external heat source, such as a gas or oil boiler, a heat pump, or a solar thermal system, circulates hot water through a coil inside the cylinder, transferring heat to the domestic water without mixing the two.

  • Key Features:
    • External Heat Source: Requires a connection to a boiler or other heating system.
    • Dual Coils (for some models): Some cylinders have two heating coils, allowing them to be connected to multiple heat sources, such as a boiler and solar panels, for maximum energy efficiency.
    • Efficiency: The efficiency of the system is directly linked to the efficiency of the external heat source (e.g., a modern condensing boiler or a heat pump).
    • Application: Best for homes with a central heating system, as it's an efficient way to provide high-pressure hot water throughout the property.

3. Slimline and Horizontal Cylinders

These categories are based on the physical design of the cylinder, offering a solution for properties with space limitations.

  • Slimline Cylinders: These have a reduced diameter compared to a standard cylinder, making them ideal for installation in narrow airing cupboards or other tight spaces.
  • Horizontal Cylinders: Designed to be installed on their side, typically in a loft space or a low-height area, for situations where vertical space is not available.

4. Integrated and Safety Features

All unvented systems, regardless of their heating method or physical design, are sealed and operate under mains pressure. For this reason, they include several crucial safety components to manage pressure and prevent overheating. These are not so much a separate category but a defining characteristic that sets unvented systems apart:

  • Expansion Vessel: Accommodates the expansion of water as it heats up, preventing pressure from building to dangerous levels.
  • Pressure-Reducing Valve: Limits the incoming mains pressure to a safe operating level for the cylinder and the home's plumbing.
  • Temperature and Pressure Relief Valve: A critical safety device that automatically discharges water if the pressure or temperature inside the cylinder exceeds a safe limit.

The primary advantage of unvented water heaters is their ability to deliver hot water at a high flow rate and consistent mains pressure to all taps and showers, improving the performance of the entire home's hot water system.

FAQs

  • What is the main advantage of an unvented water heater over a traditional vented system?

    The main advantage is the water pressure. An unvented system is connected directly to the mains water supply, so it provides hot water at mains pressure to all outlets. This results in a much stronger, more invigorating shower and faster filling of baths compared to a traditional vented system, which relies on gravity and a cold water tank in the loft. This eliminates the need for a separate shower pump.

  • Why do unvented water heaters need safety devices like an expansion vessel?

    Unvented systems are sealed and operate under mains pressure. When water is heated, it expands, which can cause a dangerous buildup of pressure in a sealed container. The expansion vessel acts as a buffer, a small tank with a flexible diaphragm, that accommodates this expansion, preventing the pressure from rising to a critical level. Other safety devices, like the temperature and pressure relief valve, are also mandatory to release water if the pressure or temperature becomes dangerously high.

  • Do I need a plumber with specific qualifications to install an unvented hot water cylinder?

    Yes, it is a legal requirement in many countries, including the UK, that unvented hot water systems be installed and serviced by a qualified professional. In the UK, this means a plumber who holds a G3 Unvented Hot Water qualification. This is because incorrect installation can be extremely dangerous. A qualified installer will ensure all safety devices are correctly fitted and functioning, and that the system complies with all building regulations.

  • Can an unvented water heater be connected to my solar panels?

    Yes, many unvented hot water cylinders are designed for this purpose. These "indirect" models often come with a second heating coil specifically for a solar thermal system. The fluid from the solar panels runs through this coil, transferring the sun's heat to the water inside the cylinder. This allows you to use renewable energy to heat your water, with your boiler or an electric immersion heater acting as a backup for cloudy days or high demand.

  • Why is my unvented cylinder's safety valve discharging water?

    If your unvented cylinder's pressure relief valve is regularly discharging water, it is a sign that there is a problem with the system's pressure management. The most common cause is a fault with the expansion vessel, often a loss of pressure in its diaphragm. It could also indicate that the pressure-reducing valve is not functioning correctly, allowing the mains pressure to enter the system unchecked. You should not attempt to fix this yourself. You should contact a G3-qualified plumber to inspect and repair the system immediately, as this is a critical safety issue.