Understanding UK Water Regulations G3: What to Know
When it comes to domestic hot water systems in the UK, Water Regulations G3 plays a critical role in ensuring safety and compliance. These regulations are particularly important for heating engineers, landlords, and property owners responsible for unvented hot water storage systems.
In this post, we’ll explore what G3 is, why it matters, and how it applies to your heating and plumbing systems.
💧 What Is G3?
G3 is a section of Approved Document G of the Building Regulations for England and Wales. It specifically covers the installation, commissioning, and safety of hot water systems, particularly unvented hot water storage cylinders.
In simple terms, G3 ensures that domestic hot water systems are safe, reliable, and protected from risks like overheating, scalding, or explosion.
🔧 What Does G3 Cover?
Water Regulations G3 addresses:
- Temperature control – Systems must have thermostats to prevent overheating.
- Discharge pipework – Proper installation of discharge pipework from safety valves to ensure safe venting of excess pressure.
- Expansion control – Systems must accommodate the expansion of water as it heats.
- Safety valves and devices – All unvented cylinders must be fitted with pressure relief valves, temperature relief valves, and expansion vessels.
- Installation standards – All work must be carried out by a competent person certified to work on unvented systems.
⚠️ Why G3 Compliance Is Essential
Failure to follow G3 regulations can lead to serious safety risks, including:
- Cylinder rupture due to overpressure
- Water leaks causing structural damage
- Risk of scalding from excessively hot water
- Legal penalties and invalidation of insurance
That's why only trained and certified engineers are legally allowed to install and maintain unvented hot water storage systems.
🛠️ Who Can Work on Unvented Cylinders?
Only professionals with a G3 Unvented Hot Water Storage Systems qualification (often referred to as a “G3 ticket”) are allowed to install or service these systems. This is separate from standard plumbing or Gas Safe certification.
At Gas-Go Heating, our engineers are G3-certified, ensuring all installations meet regulatory requirements and are completed to the highest safety standards.
📋 Key G3 Requirements for Installers
| Requirement | Description |
|---|---|
| Discharge pipe installation | Pipe must slope continuously downward and discharge safely outside |
| Tundish installation | A visible tundish must be installed to monitor discharges |
| Secondary safety devices | Must include a temperature relief valve and expansion vessel |
| Temperature limit | Hot water temperature must not exceed 100°C |
| Isolation valve | Must be accessible and close to the cylinder |
🏡 What This Means for Homeowners and Landlords
If you're having a new unvented cylinder installed—or maintaining an existing one—ensure:
- The engineer is G3-certified
- Discharge pipework is visible and safe
- Regular maintenance is carried out
- Safety devices are working correctly
Regular servicing helps keep your system safe, efficient, and compliant.
✅ Gas-Go Heating – G3 Compliant Services
At Gas-Go Heating, we carry out full installations, maintenance, and safety checks of unvented hot water cylinders in line with G3. Whether it’s a new build or a retrofit, we ensure:
- Compliance with all legal requirements
- High-quality workmanship
- Safe and efficient performance
Need Help with a G3-Compliant Hot Water System?
Get in touch with Gas-Go Heating for expert advice and fully compliant installations. We’ll assess your property’s needs, recommend the right unvented cylinder, and install it safely to meet G3 standards.
Stay safe. Stay compliant. Trust Gas-Go Heating.