Gas Water Heater: Equipotential Bonding
Equipotential Bonding
Why we install bonding cables on the metal gas and water pipes on every gas water heater replacement — and who is actually at risk without them.
Need equipotential bonding for water heater?
💬 Engage us for work done right — PUB-compliant, trusted, guaranteed.
Who touches your gas and water pipes?
Most homeowners never touch their gas water heater. It sits on the aircon ledge, out of sight. So when equipotential bonding appears on the quotation, the natural question is: who is going to get electrocuted by a pipe?
The answer: your aircon service technician.
Aircon servicing happens two to four times a year. Each time, a technician goes out to the aircon ledge where your gas water heater, its metal gas pipes, and its metal water pipes are all located alongside the aircon condenser unit. The technician handles the aircon CU with one hand and may brace against or brush a metal pipe with the other.
If the metal pipes and the aircon CU are at different electrical voltages — which happens when one is properly earthed and the other is not — the technician’s body becomes the path for the current to equalise. The current flows across the chest, through the heart.
No homeowner wants to hear that an aircon technician was electrocuted on their property. Equipotential bonding prevents this.
What is equipotential bonding?
Equipotential bonding is a cable that connects the metal gas pipes and metal water pipes to the electrical earthing system of your property. The cable ensures that all metal pipes, all metal appliances, and the electrical earth share the exact same electrical potential — the same voltage.
When everything is at the same voltage, there is no voltage difference between any two metal surfaces a person might touch simultaneously. No voltage difference means no current flow. No current flow means no electric shock.
Two levels of bonding
Main protective bonding (SS638:2018, Section 544.1). This connects the gas and water services to the electrical earth at or near the point of entry to the building. This is the building-level bonding, typically installed during the original electrical fit-out. Section 544.1.2 requires the connection to be made to “any gas, water or other service.”
Supplementary bonding (SS638:2018, Section 544.2). This is local bonding at the point where the metal pipes connect to the gas water heater — on the aircon ledge itself. This is what Homeone installs on every job. It connects the metal gas pipe and the metal water pipe to the earthing system right where the heater is, ensuring that all metal surfaces on the ledge are at the same potential.
If the building’s main bonding is absent or compromised — which is common in older properties — the supplementary bonding at the heater becomes the only path to earth for stray current on those pipes. In that scenario, it is not supplementary. It is the only bonding.
What happens without bonding
Without bonding, the metal gas pipe and the metal water pipe are electrically isolated from the earthing system. If an electrical fault occurs anywhere near either pipe — a frayed wire, a fault in the heater’s ignition circuit, stray current from the aircon CU — the pipe becomes energised. It carries voltage but has no path to discharge it safely.
Three risks
Electric shock. A person touching an energised pipe and any grounded surface simultaneously — the floor, a water tap, the aircon CU — becomes the path for the current. The current flows through their body to reach earth. Depending on the voltage and the current path, it can cause muscle lock, cardiac arrest, or death.
Fire and explosion risk. If the metal gas pipe and the metal water pipe are at different voltages, electricity can arc between them — a visible spark jumping across a gap. Near a gas pipe, an electrical arc can ignite leaking gas. Bonding keeps all metal surfaces at the same voltage, eliminating the voltage difference that causes arcing.
Invisible danger. An energised pipe looks identical to a safe one. There is no visual warning, no smell, no sound. The person who touches it has no way to know it is carrying voltage until the current enters their body.
The aircon ledge scenario
The aircon technician is on the ledge. One hand is on the aircon condenser unit (properly earthed through its own electrical connection). The other hand braces against the gas pipe or water pipe (not bonded, carrying stray voltage from a heater fault).
The voltage difference between the two surfaces sends current through the technician’s body — across the chest, through the heart.
Equipotential bonding eliminates the voltage difference. Both the gas pipe and the water pipe are bonded to earth. All surfaces are at the same potential. No current flows. No shock.
Why it is a legal requirement
Under SS638:2018 (Singapore Standard for Electrical Installations), metal extraneous conductive parts — including gas pipes and water pipes — must be effectively bonded to the electrical earthing system. This applies at both the main bonding level (Section 544.1) and the supplementary bonding level (Section 544.2).
Section 544.1.2 is explicit: the main equipotential bonding connection shall be made to “any gas, water or other service.” Both pipe types are covered.
The bonding must be installed or verified by an EMA Licensed Electrical Worker (LEW). Homeone’s quotation includes LEW supervision (S/N 13) to ensure the bonding installation complies with SS638:2018.
Electricity Act, Section 83(3)
Any person who, by rash or negligent act or omission in respect of any electrical installation, causes hurt to any person or damage to any property shall be guilty of an offence and liable on conviction to a fine not exceeding $10,000 or imprisonment for a term not exceeding 3 years, or both.
Plastic pipe exception
If your property uses non-conductive incoming plastic service pipes throughout, bonding of those pipes is generally not required because plastic cannot carry stray electricity. However, if any section of the gas or water pipe is metal — which is the case on almost all gas water heater installations — bonding is required on the metal sections.
Why most existing installations don’t have bonding
Equipotential bonding on gas and water pipes is one of the most commonly missing safety features in residential gas water heater installations. Most installers do not install it because they do not have an EMA Licensed Electrical Worker on their team and are not trained to assess electrical safety requirements.
The absence of bonding on existing installations does not mean it was not required. It means it was not done. SS638:2018 has required bonding on metal pipes for years. The fact that enforcement is rare does not change the requirement — or the risk.
Homeone installs bonding on every gas water heater replacement as standard — on both the metal gas pipe and the metal water pipe — because it is required by SS638:2018 and because the risk of not having it is real and potentially fatal.
Why the charge is $50
The bonding cables and clamps are inexpensive. The $50 covers the materials, the labour to install cables securely on both the gas pipe and the water pipe and connect them to the electrical earthing system, and the EMA Licensed Electrical Worker supervision to ensure compliance with SS638:2018.
| What you're paying for | What it means |
|---|---|
|
Material
|
Bonding cables, earth clamps, and connectors for both gas and water pipes |
|
Skilled labour
|
Route and secure bonding cables from both metal pipes to the electrical earth point |
|
Compliance
|
Installed under supervision of an EMA Licensed Electrical Worker per SS638:2018 Sections 544.1 and 544.2 |
|
1-year warranty
|
Covered under the electrical work warranty — next business day response |
The bottom line
Equipotential bonding costs $50 installed on both the metal gas pipe and the metal water pipe and prevents electrocution. The person most likely to be at risk is not you — it is the aircon technician who services your condenser unit two to four times a year on the same ledge where your metal pipes are.
Most existing installations don’t have it because most installers don’t have a Licensed Electrical Worker. Homeone does. We install it on every job because SS638:2018 requires it and because no one should be electrocuted on your aircon ledge.
Call Now +65 6742 6770
WhatsApp +65 88226770
More Articles
Related Articles
