Glass-Fused-to-Steel Tanks for Water Storage in South Sudan

Q: What are GFS tanks made of?

Low-carbon steel plates, 3 to 6 mm thick according to one manufacturer, coated with glass fired onto the steel and bolted together on site. CST describes the coating as hard and inert on both surfaces.

Q: What size is an Oxfam steel tank?

The Oxfam Supply Centre lists 11, 45, 70 and 95 cubic metre standard sizes, and Butyl Products lists 7 and 122 cubic metre sizes as well.

Tony Miller

2 days ago

6 min read

Glass-fused-to-steel (GFS) tanks suit permanent water schemes in South Sudan, not emergency response. They are bolted from factory-coated panels onto a reinforced concrete foundation. For a flooded camp, a steel tank on flat cleared ground or a Butyl bladder gets water stored sooner.

What is a GFS tank, and how is it built?

A GFS tank is a bolted steel tank whose panels carry a glass coating fused to the steel in a kiln. One manufacturer describes low-carbon steel plates of 3 to 6 mm fired with glass at temperatures between 593 and 816 degrees Celsius. The panels are bolted together on site, which is why the technology is often grouped with "rapid" storage, and why that label needs care.

The coating is the selling point. CST Industries, maker of the Aquastore range, says its glass coating forms a hard, inert barrier on both the interior and exterior surfaces and that the tanks never need repainting. The same page states that more than 100,000 Aquastore tanks have been installed in over 70 countries. That is a municipal and industrial track record. It is not a humanitarian one, and the manufacturers' pages we reviewed do not claim otherwise.

Capacity starts higher than most emergency needs. A US supplier's catalogue lists tanks from 4,000 US gallons (about 15 m³) up to 2,868,000 gallons, and lists AWWA D103 compliance across its models. For comparison, a single emergency steel tank holds 11 to 95 m³, and a small-camp storage plan is usually built from several of them rather than one large vessel.

What does a GFS tank need on the ground?

A reinforced concrete foundation, and that is the deciding constraint in most South Sudan emergencies. The specification page above calls for reinforced concrete of at least grade C30/37 under EN 206-1 for the base. It also gives an operating envelope: media with a pH between 4 and 11, at temperatures up to 60 degrees Celsius. Both are comfortable for chlorinated drinking water. The foundation is the hard part.

Compare that with the Oxfam steel tank. Butyl Products, the manufacturer, states that the tank has no base structure and can be erected on any area of flat ground cleared of debris, and recommends guy ropes and banked earth around the lower sections. The standard T95 kit is 95 m³, 6.44 m in diameter, 28 corrugated steel panels and 1,062 kg, with a PVC liner, and the Oxfam Supply Centre lists it as ready to ship in two days. Oxfam also sells an anchor bolt kit for tanks built on a concrete slab, so a slab is a choice there, not a precondition.

In a country where the road network closes with the rains, the lighter and simpler kit wins the first 90 days. Pouring and curing a C30/37 base, then lifting glass-coated panels into place, is a works contract. A steel tank on cleared ground is a crew job.

Where does GFS make sense in South Sudan?

Where the site is permanent and the money is for infrastructure, not response. Three cases fit:

Town and county water schemes. A treatment plant or borehole scheme feeding a town supply needs storage that will outlast the programme cycle. A glass-coated tank that never needs repainting removes a recurring maintenance task, which matters where the next contractor visit is weeks away.
Hospitals and health facilities. A large, hard-surfaced, easily inspected tank beside a facility that will operate for decades is a sound choice, provided a foundation can be built.
Permanent camps and consolidated settlements. When a displacement site has been planned for years rather than months, one large vessel can replace several smaller ones.

None of these describes the first weeks of a flood or an outbreak. Flooding affected over 1.4 million people across 44 counties of South Sudan in 2024 and about 1.3 million again in 2025, per OCHA. In that setting, access, ground conditions and speed decide the storage choice, and GFS loses on all three.

What should you ask a GFS supplier before you buy?

Five questions separate a serious offer from a catalogue price:

Who erects it, and where are they based? Panel bolting is simple in principle, but a tank built wrongly leaks for years. Ask for a named erection crew with references on the African continent, not a promise to "supply drawings".
Who designs and signs off the foundation? The tank is only as good as the slab under it. In flood-prone ground, ask for soil and drainage assumptions in writing.
Which standard is the tank built to, and can you see the certificate? AWWA D103 and NSF approval for potable contact are commonly claimed. CST says its glass and epoxy coatings are NSF approved and that its tanks can be designed to AWWA, EN, ISO and other standards. Ask for the document for your exact model.
How does it ship, and what is the lead time to Juba? Panels and bolts arrive over a long corridor. Ask for the packing list, the panel count per container, and who carries the risk of damage in transit.
What are the spare parts and gasket arrangements? A bolted tank is repaired panel by panel. Confirm that replacement panels and sealant can reach you without a six-month wait.

How do stored-water risks change the choice?

Storage does not protect water on its own. In South Sudan refugee camps, researchers reported that 40 to 58 per cent of households drawing from chlorinated tapstands had no detectable residual chlorine in their stored water, and that standard doses could not hold 0.2 mg/L for 24 hours. A well-built tank at the source does not fix household storage, so the tank choice sits inside a chain: treatment, bulk storage, distribution and household protection.

Sphere sets the floor for that chain: 7.5 to 15 litres per person per day, a water point within 500 metres of the dwelling, and free residual chlorine of at least 0.2 mg/L at the point of delivery. Size the tank to that demand, then treat to hold the residual. A tank you cannot dose and sample at the outlet has not solved the problem.

What does SLS supply for water storage in South Sudan?

SLS does not supply GFS tanks, and this guide is buyer guidance, not a sales pitch for them. Our storage line is the Oxfam steel tank and Butyl bladder and onion tank range, sourced as an authorised distributor and held in Juba. Our earlier piece on Butyl tanks and water security in South Sudan covers when each flexible and steel format fits.

Storage works with treatment. In the 2024-2025 South Sudan response we deployed 52M+ Aquatabs and 3.28M P&G PUR sachets, the latter to 27,344 households in Juba and Renk, as set out in our Juba cholera case study. The full range, from tanks to treatment to testing kits, is on our WASH products page.

Frequently asked questions

Are GFS tanks suitable for emergency water storage in South Sudan?

Rarely. GFS tanks need a reinforced concrete foundation, whereas the Oxfam steel tank can be erected on flat, cleared ground. GFS fits permanent schemes better.

What are GFS tanks made of?

Low-carbon steel plates, 3 to 6 mm thick per one manufacturer, coated with glass fired onto the steel and bolted together on site. CST describes the coating as hard and inert on both surfaces.

What size is an Oxfam steel tank?

The Oxfam Supply Centre lists 11, 45, 70 and 95 m³ standard sizes, and Butyl Products lists 7 and 122 m³ as well.

Does SLS supply GFS tanks?

No. SLS supplies Oxfam steel tanks and Butyl bladder and onion tanks, together with water treatment products, from Juba stock.

What residual chlorine should stored water hold?

Sphere sets at least 0.2 mg/L free residual chlorine at the point of delivery, and research in South Sudan camps found stored water often fell below it.