Is Your Tank Safe for Drinking Water? Food-Grade Materials and SABS Marks

Buying a water storage tank feels straightforward until you start reading the fine print — or discover there is no fine print at all. A surprising number of tanks sold at hardware stores, farm suppliers and online marketplaces carry no indication of whether they are safe for drinking water. Some are fine. Others are designed for irrigation, chemical storage or industrial use, and putting potable water in them can introduce contaminants you cannot see, smell or taste without laboratory testing.

This guide explains what “food grade” actually means in the South African context, how to read product markings, why second-hand containers are almost always a bad idea for drinking water, and what questions to ask before you spend money. For a broader look at storage options within a complete home backup system, see our guide to backup water systems.

What “Food Grade” Actually Means

The term “food grade” refers to materials that have been tested and confirmed safe for contact with food or drinking water. For plastic tanks — which make up the majority of residential storage in South Africa — this usually means high-density polyethylene (HDPE) or linear low-density polyethylene (LLDPE) that contains no additives, pigments or stabilisers known to leach into water at harmful concentrations.

Food-grade plastics are typically identified by their resin identification code. A recycling triangle with the number 2 (HDPE) or number 4 (LDPE) on the base of a container is a starting point, but these codes alone do not confirm food-grade status — they only identify the resin family. The manufacturer must have specified and tested the exact grade of that resin for potable-water contact.

The relevant South African drinking-water quality standard is SANS 241, published in its current 2024 edition by the South African Bureau of Standards (SABS). SANS 241 sets the chemical, physical and microbiological limits for water quality, but it does not itself certify tank materials — it defines what the water must look like when it reaches the consumer. Tank certification sits alongside this standard rather than inside it.

SABS Marks and What They Tell You

The SABS issues several types of marks. For a tank or fitting used in drinking-water systems, the most meaningful is the SABS Mark — a formal product certification indicating that a manufacturer’s product has been independently tested and found to meet a nominated standard. When you see a genuine SABS mark on a tank, it means the SABS has audited both the product and the production process against documented requirements.

A few things to know:

• The mark must appear on the product itself or its permanent labelling, not only on a brochure or website.
• You can verify an SABS-marked product by contacting the SABS directly or checking with the manufacturer for their certification number.
• Some imported tanks carry international equivalents (NSF/ANSI 61 from North America, or WRAS approval from the UK). These are generally recognised as credible but are not South African certifications.

If a supplier cannot produce any documentation and the tank carries only a generic recycling symbol, treat that as a gap you need to resolve before purchase — not after.

Tank Materials Commonly Used in South Africa

The table below summarises the materials you will most often encounter and their typical suitability for potable water storage.

Material	Typical potable-water use	Key considerations
HDPE (polyethylene)	Yes, if food-grade specified	Most common; UV-stabilised versions needed outdoors
Fibreglass (GRP)	Yes, if correctly lined	Inner coating matters; old or damaged linings can leach
Galvanised steel	Generally not recommended	Zinc and other coatings can contaminate water over time
Concrete	Yes, with proper sealing	Alkalinity can affect taste and pH; needs specialist assessment
Repurposed drums	Rarely safe	Prior contents almost never fully removable

Fibreglass tanks deserve a specific note: the resin system and inner coating used during manufacture determine whether they are safe for potable water. A fibreglass tank built for irrigation or chemical storage can look identical to a potable-water tank from the outside. Always ask the manufacturer for the liner specification and any test data.

For a detailed comparison of tank materials — including longevity, maintenance requirements and cost differences — read our article on water tank materials.

Why Reused Chemical Drums Are a Serious Risk

It is common in South Africa to see repurposed industrial intermediate bulk containers (IBCs) or 200-litre drums sold cheaply at markets or advertised online for water storage. These containers often look clean and robust. The risk is not what you can see.

Many industrial chemicals — solvents, pesticides, fertiliser concentrates, cleaning agents — bind to plastic at a molecular level. Even after thorough washing, trace residues can remain in the pores of the plastic and leach slowly into stored water. The Water Research Commission (WRC) has documented this as a significant informal-sector water-safety concern. There is no reliable domestic cleaning method that makes a formerly chemical-contaminated drum safe for drinking water. If you are unsure of a container’s history, do not use it for potable storage.

If you want a potable-water storage setup you can trust from day one, it helps to get the tank and installation assessed together. Compare 3 free quotes — vetted installers, no obligation.

Fittings, Connectors and Inlet Pipes

A food-grade tank paired with non-potable fittings is only as safe as its weakest component. Brass fittings containing more than trace levels of lead, PVC pipes with non-approved plasticisers, and rubber seals not rated for drinking water can all introduce contaminants regardless of the tank’s own certification.

When specifying a system, ask your installer or supplier to confirm that every component in contact with stored water — inlets, outlets, floats, overflow fittings, pipe jointing compound — is specified for potable-water use. This is standard practice for competent installers but is worth raising explicitly.

Understanding what potable water means as a standard — and what compromises it — helps you ask sharper questions when comparing options.

Keeping the Tank Safe After Installation

Even a correctly specified, fully certified tank can become a contamination source if it is not maintained. Stored water can harbour bacteria if tanks are infrequently cleaned, improperly covered, or exposed to light in ways that encourage algal growth. Dark or opaque tanks reduce this risk compared with translucent containers.

As a general principle: test first, treat second. Before relying on any stored water for drinking or cooking, have a sample tested by an accredited laboratory against SANS 241 parameters. This is especially important at initial commissioning and after any extended period of non-use or tank maintenance.

For practical guidance on rotation, cleaning schedules and preventing stagnation, see our detailed post on keeping stored water fresh.

Choosing the right tank is one part of a well-designed backup water system — getting the full picture from an experienced installer makes the rest easier. Get matched with up to three vetted installers — free, no obligation.

What to Ask Before You Buy

Here is a practical checklist when evaluating any tank for drinking-water storage:

1. Is the tank specifically specified by the manufacturer for potable water? Ask for written confirmation, not just a verbal assurance.
2. Does it carry an SABS mark or equivalent certification? Ask for the certification number or reference standard.
3. What is the resin grade and any additive specification? Food-grade HDPE should use approved UV stabilisers only.
4. For fibreglass tanks: what is the inner liner? Get the liner specification and any available test data.
5. What is the container’s history? For any second-hand container, the answer needs to be fully traceable.
6. Are all fittings supplied rated for potable water? Ask this as a separate question — suppliers sometimes assume you only want a tank price.

No reputable supplier will object to these questions. If a supplier cannot or will not answer them, that is information in itself.