Let's Talk
Large steel bulk tank with sealed base

Why Bulk Storage Tanks Need Waterproofing in Gauteng

Leave a Comment / General / By

Bulk storage tanks need waterproofing because water, in the wrong place, is what damages them. Moisture at the base corrodes steel. Cracks in a concrete wall let stored liquid out and groundwater in. Soil that shifts under the tank puts stress on joints and welds. In Gauteng, where many sites sit on clay soils that move with moisture, a tank that is sealed and drained properly lasts longer, loses less product and puts less at risk around it.

This guide is for industrial and commercial owners, facilities managers and investors who run water, process or fuel storage on Gauteng sites. It explains what goes wrong, why local ground conditions matter, what to consider for a new tank or an existing one, and how to brief a waterproofing contractor.

Prowaterproofing
Protect Your Tank From Water Damage
Prowaterproofing offers waterproofing solutions for industrial properties, helping owners address moisture risks to bulk storage tanks.
Explore waterproofing services

TL;DR

  • Waterproofing protects a bulk tank from corrosion, cracking and leakage, and protects the ground and buildings around it from what escapes.
  • Expansive clay soils, common across parts of Gauteng, shift as moisture changes and can push on tank walls and foundations.
  • A new concrete tank is waterproofed through good design and mix. An existing tank needs a diagnosis first, then crack and joint repair, then a compatible lining or coating.
  • Lined tanks need scheduled inspection, not a one-off treatment.
  • Before you hire, ask about licensing, experience with tanks, the product’s compatibility with the stored liquid and the written warranty.

Table of Contents

What waterproofing does for a bulk storage tank

A bulk tank is a container whose job is to keep one liquid in and everything else out. Waterproofing supports both halves of that job. On the outside, it keeps rain, groundwater and condensation away from the structure. On the inside, a lining or sealed surface keeps the contents from seeping through concrete or attacking steel.

The stored liquid also matters. Research on domestic drinking water tanks notes that storing water always changes its quality, because chemical, physical and microbiological processes continue while the water sits in storage. The same review treats keeping quality as high as possible as the main aim. The US Environmental Protection Agency makes a related point about public supply: water in a pipe is protected because pressure keeps pushing outwards, but water in a storage tank is more vulnerable, so every tank component needs sound sanitary practice. A sealed, intact tank surface is part of that.

For tanks holding fuel, chemicals or process liquids, the stakes change from quality to containment. A leak is then a site safety and environmental problem as well as a cost.

Why Gauteng conditions raise the stakes

Gauteng is a mix of highveld industrial parks, mining-belt land and fast-growing commercial developments. Ground conditions differ from one site to the next, but one issue comes up again and again: clay.

A South African write-up on commercial underground tanks notes that expansive clay soils, common across parts of Gauteng and the Western Cape, shift with moisture changes and can exert lateral pressure on tank walls. A tank sitting in that soil is pushed and released as the ground wets and dries. Over years, that cycle can open hairline cracks in concrete, loosen joints and stress the connection between a tank’s base and its walls.

Two practical consequences follow:

  1. Water finds the cracks. Once a crack opens, groundwater can enter an empty or part-full tank, and stored liquid can leave a full one.
  2. Small defects grow. A crack that is sealed early is a maintenance item. A crack left through several wet seasons can expose reinforcing steel and become a structural repair.

Your own site’s soil, drainage and water table matter more than any general rule, which is why a survey comes before any product choice. For the wider case for sealing structures in the region, see our article on why waterproofing protects structures in Gauteng.

Ground movement, settlement and soil pressure

Tanks are heavy, especially when full, and they rest on a foundation that is only as stable as the soil beneath it. Engineering research on steel tanks shows what uneven support does. A Polish study of a failed cylindrical steel tank explains that settlement of the subsoil under the tank bottom creates high stresses where the bottom meets the shell, and in extreme cases the bottom or the shell edge can yield and crack.

The UK tank foundation guidance EEMUA 159 describes the mechanism in more detail. It states that uneven settlement puts the bottom edge at greater risk than even settlement, because the thin flat bottom plates follow the uneven pattern and the tank tries to bridge areas that sink more. That can ultimately rupture the inner fillet weld joining the bottom to the shell. The same document is balanced: even settlement is generally not dangerous, because it is gradual and uniform, but when it becomes excessive the tank may need remedial action and the extent of settlement should be checked.

What this means for a Gauteng owner: movement is normal, and what hurts is movement that is uneven or unmonitored. Waterproofing does not stop the ground moving. It keeps the tank’s surfaces sealed and flexible enough to cope, and it keeps water out of the foundation, where it can make settlement worse.

Ground movement, settlement and soil pressure

What a leak actually costs

A tank leak has three kinds of cost: lost contents, damage to the tank itself, and damage to everything around it.

Lost contents and wasted water

Leaks can be large even when they are slow. A 2019 study of a 45,000 m³ reinforced concrete water tank in Poland found water losses of roughly 110,000 to 150,000 m³ a year. The authors linked the leaks to insufficient wall reinforcement against concrete shrinkage and to faulty design of the bottom slab expansion joints. Your tank is unlikely to be that size, but the lesson scales down: joints and shrinkage cracks are where concrete tanks leak, and they are exactly where waterproofing detail work counts.

Damage to the foundation

EEMUA 159 warns that leakage from a tank bottom means product is penetrating into the foundation, which can be serious for the tank’s safety and can pollute the soil. It adds that leakage near the edge of the shell should be treated as a major problem needing urgent attention, because it may wash out the foundation beneath the shell. A leak that undermines the foundation makes the next leak more likely.

Risk to the surroundings

For underground or mounded tanks holding flammable liquids, the UK Health and Safety Executive notes in HSG176 that leakage from damage or corrosion may be difficult to detect. It can contaminate the ground, surface water and groundwater, and create fire and explosion risks for nearby buildings and basements. That guidance is British, so check the South African requirements that apply to your liquid and site, but the logic carries over: a leak you cannot see is the dangerous one.

Corrosion from the outside in

On steel tanks, moisture is the starting point for corrosion. The US EPA identifies corrosion, improper installation and poor operating practices as the three main causes of leaks from underground storage tanks. It notes that electrolytic and galvanic corrosion occur when soil acts as an electrolyte between dissimilar metals, or when stray electric currents enter the structure. For above-ground industrial tanks, a South African industrial coatings supplier notes that moisture collects at the chime angle or under the base after bad weather and condensation, leading to base corrosion, leakage and ultimately tank failure. It also points out that traditional sealing methods such as mastic tapes can shrink and degrade under UV, and do not let trapped moisture escape.

How tank type, location and contents change the requirement

There is no single waterproofing specification for “a tank”. The right approach depends on four things.

Factor What it changes
Material (concrete, steel, polyethylene) Concrete needs crack and joint sealing and permeability control. Steel needs corrosion protection. Polyethylene faces UV and temperature stress.
Location (below ground, mounded, above ground) Buried tanks fight groundwater and soil pressure. Above-ground tanks fight rain, condensation at the base, UV and wind.
Contents (potable water, process water, fuel, chemicals) The lining or coating must be compatible with the liquid, and potable storage has hygiene demands.
Climate and site Heavy rain, temperature swings and drainage affect how moisture reaches the tank.

The UK HSE advises that tank materials and linings should be compatible with the chemical and physical properties of the liquid, so that nothing interacts in a way that causes failure. This is the single most common specification question we would expect from a good contractor: what is in the tank, at what temperature, and for how long?

HSE guidance also notes that storage at ground level in the open air has advantages, because leaks are more readily detected and contained and corrosion is easier to identify and control. Visibility is worth designing for.

Rain load matters on open or roofed tanks too. Nova Scotia’s environment department warns that water pooling on a tank roof during heavy rainfall or snowfall can cause roof failure in places or across the whole roof, and product may be displaced or the tank may rupture. Snow is rare on the Highveld, but heavy summer storms make drainage and roof falls a real design point. The same guidance says above-ground tanks in flood-prone areas should be securely anchored, with design by a professional engineer.

New tank or existing tank: what to consider

The approach splits cleanly in two.

Waterproofing a new concrete tank

For a new reinforced concrete tank, most of the waterproofing is done by getting construction right. A tank waterproofing guide lists structural design and crack control, concrete mix, admixtures, reinforcement, waterstops, compaction and curing as the points to settle. It explains that an integral waterproofing admixture mixed into the concrete or mortar reduces permeability during construction. Waterstops at construction joints and proper curing do much of the remaining work.

Decide the waterproofing strategy before the pour, not after. Retrofitting a joint that was never detailed for a tank is always harder than detailing it at the start.

Repairing and waterproofing an existing tank

Existing tanks need diagnosis first. The same guide advises that you identify the leak source, remove weak concrete, repair cracks, joints and honeycombing, then select a compatible coating or lining. Crack treatment follows a clear logic. Guidance on liquid containment structures says the cause of a crack must be analysed and classified as active or dormant, and verified as non-structural, unrelated to steel corrosion, before a repair method is chosen.

Crack along an interior concrete tank joint

The same source describes the options for active cracks: pressure injection with chemical grouts, routing and sealing with a flexible sealant, or a joint-free liquid-applied flexible membrane on the liquid side. These are serviceability repairs rather than structural ones. A flexible, seamless membrane suits tanks on moving ground because it bridges small movements. Our article on liquid membrane waterproofing in Gauteng explains how these systems work on buildings, and the principle is the same for a concrete tank or bund.

A useful sequence for an existing tank:

  1. Empty and clean the tank safely, following the rules for its contents.
  2. Inspect the surfaces and map cracks, joints, honeycombing and exposed steel.
  3. Establish whether cracks are moving or stable, and whether any are structural.
  4. Cut out weak concrete and repair defects.
  5. Seal joints and cracks with products suited to movement and to the stored liquid.
  6. Apply the compatible lining or membrane.
  7. Test and document the result, then agree an inspection schedule.

Below-ground concrete has the same moisture pressures as a basement. If your site also has basements or plant rooms next to the tank, see our guide to waterproofing basement floors in Gauteng.

Inspection and maintenance

Waterproofing is not a one-time job. Linings age, joints move and coatings wear. Inspection is how you catch the next problem while it is still a repair.

Some regulators set a fixed rhythm. As an example from the United States, Minnesota’s pollution control agency says internally lined underground tanks must be emptied and inspected by a qualified professional within 10 years of lining installation and every five years after that, under API 1631. The inspection covers cleaning, visual checks, ultrasonic shell thickness, holiday (pinhole) testing, and lining thickness and hardness. That is a Minnesota rule, not a South African one, but it shows what a thorough inspection includes and how often it is sensible to look.

A practical routine for a Gauteng site:

  • Walk the tank base and perimeter after heavy rain and look for pooling, staining or damp at the foundation.
  • Keep drainage, bunds and gutters clear.
  • Record any new cracks with photographs and dates.
  • Schedule a full internal inspection on the interval set by your engineer, the lining manufacturer or the regulations for your liquid.
  • Keep the contractor’s warranty and product data sheets with your site records.

Our view: ask the right questions before the first coat

Most tank problems we hear about are not caused by a bad product. They come from a skipped diagnosis, a lining chosen without checking what goes in the tank, or a contractor who could not explain the warranty.

That is why we put the questions first. We built Pro Waterproofing around helping owners judge contractors on quality, experience, licensing and warranties, and around practical, region-specific guidance for Gauteng and the Western Cape. For a bulk tank, that means asking who has done similar work, what the product is rated for, how movement in the substrate is handled, and what the warranty actually covers in writing.

Waterproofing a tank is cheaper than replacing one, and far cheaper than cleaning up after a leak. Do it once, do it properly, and get it documented.

Eben

Choosing a waterproofing contractor for a tank

A tank is not a flat roof. The contractor needs to understand containment, compatibility and movement. Before you accept a quote, ask:

  • Licensing and registration. Can they show the credentials the work requires?
  • Relevant experience. Have they worked on tanks, reservoirs or bunds, and can they describe a comparable job?
  • Diagnosis. Will they inspect and identify the leak source and crack behaviour before pricing a solution?
  • Compatibility. Will they confirm in writing that the system suits your stored liquid and temperature?
  • Warranty. What does it cover, for how long, and what maintenance does it require?
  • Sequence and safety. How will they handle emptying, ventilation and access to the tank?

Compare quotes on scope, not just the total. A cheaper quote that skips crack classification or surface preparation is not like for like.

Get a quote for your tank

Pro Waterproofing connects property owners and managers across Gauteng with waterproofing professionals for residential, commercial and industrial buildings, including roofs, basements, foundations and concrete decks. If you are planning tank or bund waterproofing, tell us what is stored, where the tank sits and what you have noticed, and we will help you move to a quote with the right questions already asked.

Prowaterproofing

Request a waterproofing quote to get started. If the tank sits on or beside a roof slab, our guide to roof slab waterproofing in Gauteng shows how we think about concrete decks. We also cover Johannesburg and nearby areas such as Midrand and Germiston.

FAQ

Why do bulk storage tanks need waterproofing?

Waterproofing keeps moisture away from tank surfaces and keeps stored liquid inside. It reduces corrosion on steel, seals cracks and joints in concrete, and protects the foundation from washout. It also limits the risk of contamination to the ground and nearby buildings.

Does Gauteng’s soil make tank waterproofing more important?

Often, yes. Expansive clay soils found in parts of Gauteng shift with moisture and can press on tank walls and foundations. Over time that movement can open cracks and joints, so a flexible, well-detailed waterproofing system is a sensible response. A site survey will confirm what your ground is doing.

Can an existing tank be waterproofed, or does it need replacing?

Many existing tanks can be repaired and sealed. The usual process is to find the leak source, remove weak concrete, classify cracks as active or dormant, repair them and apply a compatible lining. Structural damage or corroded steel needs an engineer’s assessment first.

How often should a waterproofed tank be inspected?

There is no single interval for every tank. It depends on the material, the liquid, the lining manufacturer’s guidance and the rules that apply to your site. As a reference point, one US regulator requires inspection of lined underground tanks within 10 years of lining and every five years after. Ask your contractor to put an inspection schedule in writing.

Sources

Leave a Comment