2 Apr 2025

7 Hidden Health Risks Of Storage Water Heater Contamination

7 Hidden Health Risks of Storage Water Heater Contamination

Introduction of Storage Water Heater Contamination

Storage water heaters provide convenient access to hot water but can pose significant health risks if improperly installed or inadequately maintained. Since 2018, Singapore’s Public Utilities Board (PUB) has mandated that all installations must be carried out exclusively by licensed plumbers.

This article identifies common contamination risks—including backflow, corrosion, sediment build-up, and bacterial growth—and outlines effective preventive measures to ensure safe water quality in your home.

Common Sources of Contamination

Backflow into the Water Supply

Risk: Historically, over 90% of storage water heaters in HDB flats lacked essential anti-backflow protection, as checks on renovations, particularly plumbing, were rarely enforced by HDB and PUB. Without proper controls, heated water can flow back into the cold water supply, potentially contaminating drinking water with bacteria and heavy metals, affecting multiple households.

Prevention:

Install a certified double-check anti-backflow valve as required by PUB.
Always engage PUB Licensed Plumbers and obtain the necessary compliance certificates.

Corrosion and Leaching from Tank Materials

Risk: Tanks made from unlined steel or inferior materials can corrode over time, releasing harmful substances such as lead and iron into stored water.

Prevention:

Choose water heaters with stainless steel or high-quality glass-lined tanks.
Regularly inspect and replace the anode rod every three years in glass-lined tanks.
Replace storage water heaters older than ten years.

Sediment Accumulation

Risk: Sediment originating from rooftop water tanks can accumulate in storage heaters, creating an ideal environment for harmful bacteria such as Legionella. Historically, rooftop tank maintenance managed by MCSTs or town councils faced compliance issues; however, PUB’s introduction of Qualified Checkers (QCs) has significantly improved maintenance practices.

Prevention:

Flush your storage heater tank annually to remove sediment build-up.
Report any concerns regarding rooftop tank maintenance to PUB or authorised Qualified Checkers (e.g., One Centum Pte Ltd, Mei De Engineering Pte Ltd).

Inadequate Temperature Control

Risk: Water temperatures below 60°C create favourable conditions for Legionella bacteria, which thrive between 20°C and 50°C.

Prevention:

Consistently maintain thermostat settings above 60°C.
Regularly monitor water temperature using a reliable thermometer.

PUB Regulations: Your Primary Defence

PUB strictly regulates storage water heater installations in Singapore:

Mandatory installation of certified double-check anti-backflow valves.
Compliance with AS/NZS 4020:2018 to prevent hazardous substance leaching.
Only licensed plumbers are permitted to install and service water heaters.

Non-compliance can result in substantial fines and potential health hazards.

7-Step Prevention Checklist

Hire Licensed Plumbers: Always engage PUB Licensed Plumbers for installation and servicing, rather than unlicensed handymen.
Ensure Proper Submission to PUB: Confirm that the Licensed Plumber genuinely oversees the work and submission processes, rather than just using their credentials for marketing.
Avoid Rubber Stamp Practices: Be cautious of plumbers who submit generic documentation without proper verification, known as “rubber stamping.” PUB may not verify every submission.
Install Anti-Backflow Valves: Ensure certified double-check valves are correctly installed.
Control Temperature: Maintain thermostat settings between 60–65°C.
Annual Maintenance: Flush tanks annually to reduce sediment and bacterial risks.
Use Cold Water for Consumption: Always use cold tap water for drinking and cooking.

Conclusion

Storage water heaters are convenient and essential household appliances; however, improper installation or poor maintenance can severely compromise water quality. By understanding contamination risks—such as backflow, corrosion, sediment accumulation, and bacterial growth—you can effectively safeguard your household’s water supply. Adhere strictly to PUB regulations, perform regular maintenance, and rely exclusively on licensed plumbing professionals.