A gas boiler and a water cylinder with immersions are often confused, and most people just call any heating unit a “boiler.” While that’s fine in casual conversation, knowing the exact heating system you have is important when it comes to maintenance, reporting faults, and keeping your hot water running smoothly. In this guide, we explain the key differences so you can accurately describe your unit and get the right help when needed.
1. Appearance and Location
Gas Boiler
- Usually wall-mounted and compact.
- Connected to gas lines and water pipes (inlet and outlet).
- Often comes with a digital display or control panel.
Water Cylinder with Immersions
- Also called a hot water tank, typically tall and cylindrical.
- Usually found in lofts, airing cupboards, or other storage spaces.
- Larger than a boiler and rarely wall-mounted.
Tip: Size and location are usually the easiest way to tell the two apart.
2. Purpose
Gas Unit
- Heats water for central heating and domestic use.
- Circulates hot water through radiators or underfloor heating and delivers hot water to taps and showers.
Hot Water Tank
- Stores and heats a large volume of water for domestic use.
- Uses electric immersion heaters, often as a backup or primary source for hot water storage.
- For more guidance on efficient hot water systems and how immersion heaters work in Irish homes, see the SEAI guide.
3. Functionality
Gas Boiler
- Provides on-demand hot water and central heating.
- Thermostats and timers allow control over temperature and schedules.
- Some models have a reset button to fix minor issues quickly.
Immersion cylinder
- Primarily stores hot water.
- Immersion heaters can be manually controlled with timers or boost switches.
- Both top and bottom immersions should work to avoid running out of hot water.
4. Maintenance
Gas Unit
- Requires annual servicing for gas safety checks and general maintenance.
- Checking the digital panel for error codes before contacting a professional can save time.
Water Cylinder with Immersions
- Maintenance focuses on checking the immersion heaters and timers.
- If one immersion isn’t working, you may still get hot water, but both should be functional to prevent bigger problems.
5. Key Takeaways
Understanding whether you have a gas boiler or a water cylinder with immersions helps you:
- Communicate clearly with maintenance professionals.
- Troubleshoot minor issues more effectively.
- Keep your hot water system running efficiently.
Pro Tip: No hot water doesn’t automatically mean a plumber is required—sometimes it’s an electrician who can resolve the issue.
Need Assistance?
If you notice a problem with your heating system or have any questions, please submit a property issue report through our Earnest Fixflo system or contact us directly