By Dr. Arthur L.C. Antoine, Ph.D., P.E., PMP, DBIA
In the Caribbean, where water insecurity is a daily reality, household water tanks are more than a convenience—they’re essential. However, as our communities install more black plastic tanks to harvest rainwater or store potable water, we must pause and ask: Are we really using them safely?
Sadly, we’re not a research-based society, and too often, decisions around our built environment and public health are driven by habit, hearsay, or short-term fixes. With rising concerns about unexplained health issues—including growing suspicion about increased cancer cases—many are beginning to ask a valid question: Is something in our water?
Once a tank is installed—often perched high on a concrete platform or building rooftop—it remains there for decades, neglected and assumed safe. In this article, we aim to unpack the real facts behind those familiar black tanks found across rooftops, backyards, and balconies in Saint Lucia and across our region.
Why We Use Black HDPE Tanks—and Why They’re Popular
The black plastic tanks we commonly see are typically made from high-density polyethene (HDPE), a material chosen for good reason. These tanks are often food-grade and BPA-free, meaning they are generally safe for storing drinking water if properly selected and maintained.
The black colour isn’t just for aesthetics, it’s functional. It blocks out sunlight, which helps prevent algae growth, a common issue in our hot and humid Caribbean climate. HDPE is also resistant to rust and corrosion, making these tanks a logical choice over metal or concrete in salty coastal environments.
Here’s the catch: not all tanks are created equal, and how you use and maintain them is just as important as the material they’re made from.
Risks Hiding in Plain Sight
Let’s talk about what can go wrong…
Some tanks sold in hardware stores or shipped in bulk may not be certified for potable water. Although tanks made for agriculture or industrial use may look similar to potable water tanks, they can leach harmful chemicals into the water over time. If your tank isn’t labelled as compliant by appropriate local/international standards (e.g., NSF/ANSI 61, FDA standards, or an equivalent), it’s worth a second look—or replacing.
UV damage is another real threat. Over time, tanks that aren’t UV-stabilised can degrade in the sun, causing microplastics or chemical byproducts to seep into the water. And while your tank may seem sturdy, bacterial growth inside can be invisible and dangerous, especially if you’ve never cleaned it.
Even food-grade tanks are not immune to biofilm buildup, where bacteria thrive on the inside walls. Once this occurs, simple flushing won’t be enough. Contaminated water may look clear and could still make you or your family sick.
Recommended Simple Steps to Make Your Tank Safer
The good news? Ensuring your water storage is safe isn’t rocket science; it just takes awareness and basic maintenance.
- Check Tank Certifications
Always purchase tanks certified for potable water use. Look for relevant international certifications or seek advice from our Saint Lucia Bureau of Standards (SLBS). - Rainwater tank? Avoid the “First-Flush”
If your tank collects rainwater, attempt to avoid roof debris, bird droppings, and other contaminants in your supply. Consider controlling the first-flush/runoff into your tank or technical solutions such as a first-flush diverter. - Clean Regularly
Clean the tank every 6–12 months using a mild chlorine solution or a safe disinfectant. Drain the tank, scrub the inside if possible, and refill only after thoroughly rinsing. Seek help from local plumbers/contractors. - Flush Before First Use
Of course, when a new tank is initially installed, it may carry a plastic taste or odour and need to be flushed several times before drinking the water to minimise this effect. - Use Safe Plumbing
Avoid connecting the tank using unsafe components like lead-based fittings or low-grade plastics that degrade over time. - Watch for Red Flags
Be alert to changes in the taste, smell, or appearance of water. Slippery surfaces inside the tank, odour, or discolouration are signs that a thorough cleaning is overdue. Pay close attention to tanks that have been left unused for extended periods, e.g., in vacant rental properties, as they may harbour stagnant water, biofilm buildup, or other contaminants.
A Matter of Public Health and Common Sense
It’s time we treat water tank safety as a public health issue, not just a homeowner’s chore. These tanks are often overlooked after installation; however, the health of an entire household can be compromised by what seems like a minor detail.
Let’s shift from being a society that installs and forgets to one that inspects, maintains, and informs. Our health, and that of our next generation, depends on it.
Dr. Arthur L.C. Antoine, PE, PMP, DBIA, is a Saint Lucian-born professional Civil and Ocean Engineer and an international project delivery expert with over 20 years of experience leading complex infrastructure and construction projects. Dr. Antoine has contributed as both a practitioner and researcher to capital infrastructure initiatives globally. He has served in senior roles with multinational engineering firms and multilateral agencies, advising on transportation, water infrastructure, disaster mitigation, and public procurement. As a strong advocate for inclusive development and STEM access, he is passionate about demystifying engineering for the everyday citizen while guiding public and private sector clients to make smarter, data-informed investment decisions.