Water Tanks for Ebola Isolation and Treatment Sites: Which Type, How Big, How Fast

Tony Miller

2 days ago

7 min read

Size storage for an Ebola treatment site from UNICEF's planning range of 100 to 400 litres per person per day, and hold at least two days of that demand on site. Use bladders to open the site, Oxfam steel tanks to run it, and keep the tank farm on its own supply line.

This piece covers the storage decision only. It uses standing guidance and manufacturer specifications. It says nothing about the current state of any outbreak, because that changes weekly and belongs to WHO and Africa CDC, not to a supplier.

How much water does an Ebola treatment site need?

The planning range is 100 to 400 litres per person per day. UNICEF's 10 October 2014 guidance note on the WASH package for Ebola care and treatment centres puts the total supply needed for cleaning, laundry, chlorinated hand washing, footbaths, disinfection of materials and bodies, drinking and preparing oral rehydration solution at 100 to 400 litres per person per day. That is far above the Sphere minimum for basic survival needs of 7.5 to 15 litres per person per day, because most of the water is used for infection control, not drinking.

Field practice sits at the top of that range. International Medical Corps, writing in May 2019 about the DRC response, cited 150 litres per patient per day in the 2014 to 2016 West African outbreak and about 400 litres per bed per day as the working figure for treatment centres in DRC. The same article says DRC treatment units must hold a minimum of three days of water at all times.

My view: plan on the high end for the tank farm and be pleasantly surprised if you use less. Undersized storage on an isolation site is not an inconvenience. It means decontamination, laundry or hand washing is rationed on a site whose whole purpose is infection control.

How big should the tanks be?

Multiply people on site by the planning range, then by your buffer in days. The UNICEF note asks for storage of at least two days, and says to monitor water quality daily and keep a two-day consumption buffer. Because storage is only a buffer against supply failure, count everyone drawing water: patients, clinical staff, cleaners, laundry and waste teams.

An illustration, which is my own arithmetic and not a figure from any source. A site with 50 people drawing water:

At 100 litres each, daily demand is 5 m³, so a two-day buffer is 10 m³.
At 400 litres each, daily demand is 20 m³, so a two-day buffer is 40 m³.
At the three-day buffer International Medical Corps describes for DRC units, the 400-litre case is 60 m³.

Oxfam steel tank kits come in four sizes, 11, 45, 70 and 95 m³. One 45 m³ tank covers the two-day, 400-litre case above; one 70 m³ tank covers the three-day case. Two smaller tanks beat one large one when you need to isolate a tank for cleaning without losing supply, which brings us to the main design rule.

Which tank type fits an Ebola site?

Match the tank to the phase of the site, not to the catalogue.

Collapsible bladder, for the first days. The Oxfam 10 m³ bladder kit is a closed tank in food-grade PVC-coated polyester with heat-welded seams, a 2 inch outlet and a screwed filler cap, weighing 98 kg. It needs only reasonably level ground, because on a slope it rolls when filled, and it ships with a groundsheet. Oxfam also lists 5 and 20 m³ bladders on its flexible tanks page, described as first-phase kits where speed and portability matter. It is the right way to put water on a cleared plot before anything permanent is built.
Oxfam steel tank, to run the site. Corrugated steel panels with a PVC liner and a roof, erected on a prepared base. The 70 m³ kit is 6.44 m in diameter, supplied as steel sheets, liner kit and low-profile steel roof, with 3 inch gate-valve outlets, and weighs 931 kg. Where it stands on a concrete slab an anchor bolt kit is required. For a site that will operate for months it is the better storage: durable, roofed, repairable and easy to clean.
Onion tank, as a mid-point. Oxfam lists 10 and 30 m³ onion kits. They suit a fast, mid-size need, but check how the cover and filler are closed before you accept one on an isolation site. Our comparison of onion tanks and bladders goes through that trade-off.

The sequence I would specify: bladders on day one, steel tanks within the first weeks, bladders retained as reserve and for the transit or reception area. SLS is an authorised distributor for Oxfam and Butyl tanks and stocks in Juba; we do not supply glass-fused-to-steel tanks, so this guide does not recommend them.

How fast can you erect storage?

Bladders are fast, and steel tanks are slower and need skilled hands. Oxfam does not publish an erection time on its tank pages, and a quoted figure from a supplier who has not seen your site is a guess. Ask for it in writing with the crew size and tools assumed.

What the specifications do tell you is where time goes:

Base preparation. MSF's catalogue entry for the 45 m³ Oxfam tank calls for an even, stable, horizontal platform accessible in all circumstances, because a filled tank is heavy. Its diameter is 6.4 m. Clearing and levelling that footprint is usually the long pole.
Plinth. To get gravity head the plinth kit for T45, T70 and T95 tanks is a corrugated steel ring filled and compacted with earth and rubble in 15 cm layers, to a maximum height of 1.5 m, on a compact, level foundation dug about 10 cm deep with drainage in place. Budget the compaction time.
Liner and roof. Assembly of the liner and roof comes after the steel is up. Oxfam's own tank installation training covers site selection, base, steels, liner, roof and commissioning as separate skills, which tells you something about the sequence.
Head over the tap stands. MSF's entry says to place the tank at least 1.2 m above tap stands for gravity distribution, and Oxfam's bladder page says about 1.5 m. Otherwise you are adding a pump and a power source to the site.

How do you keep stored water safe on an isolation site?

Keep the tank farm off the staff supply and behind a non-return valve. UNICEF's note says connections and water lines to facilities, including wards, laboratories and storage tanks, should be separate from lines supplying water to staff, and that any line to a facility should have a non-return valve. A site that lets contaminated back-flow reach a tank has defeated its own purpose.

Beyond that:

Choose closed or roofed storage and keep filler caps and hatches shut.
Fence the tank perimeter and protect embankments from erosion, as MSF's tank entry advises, and secure with ropes in windy areas.
Treat and test. Sphere's minimum is 0.2 mg/L free residual chlorine at the point of delivery, and in South Sudan refugee camps research found that 40 to 58% of households on chlorinated tapstands had no detectable residual in stored water. Heat and a long residence time drain chlorine. Test daily, as UNICEF's note directs.
Clean tanks regularly. UNICEF's note says to clean storage containers regularly; your agency's protocol sets the method.

Chlorine solutions, dosing for infection control and facility IPC protocols are outside what a tank supplier should write. Follow your agency's and WHO's guidance. Our existing post on chlorine, water storage and supply planning for treatment units covers the wider supply side. For stored-water treatment, Aquatabs 67 mg NaDCC tablets are dosed to the manufacturer's instruction sheet.

What should a buyer ask the supplier?

Five questions decide the order:

Is the supplier the authorised distributor, and is the stock in the country? Our WASH products ship from Juba.
What is in the kit, and what is not? The Oxfam 11 m³ listing notes Guillemin fittings are ordered separately, and the larger kits recommend a tank tool kit, scaffolding tower and ladder.
What is the base, and who prepares it?
Who erects it, and is there a person on site who has done it before?
What is the lead time to the site, not to the port?

Our case studies show what in-country delivery looks like in practice.

Frequently asked questions

How much water storage does an Ebola treatment centre need?

UNICEF's guidance note estimates 100 to 400 litres per person per day and asks for at least two days of storage. International Medical Corps reports a three-day minimum in DRC treatment units.

Which water tank is best for an Ebola isolation site?

Use collapsible bladders to open the site and Oxfam steel tanks, in 11, 45, 70 or 95 m³, for sustained operation, because they are roofed, repairable and cleanable.

Does a tank need a special base?

Yes. A bladder needs reasonably level ground or it rolls when filled, and MSF specifies an even, stable, horizontal platform for steel tanks. A concrete slab base needs the anchor bolt kit.

Should the tank supply line be shared with staff areas?

No. UNICEF says supply lines to facilities and storage tanks should be separate from staff supply lines, with a non-return valve.

Does SLS supply PPE, chlorine solution or treatment-unit equipment?

No. SLS supplies water storage, treatment tablets and sachets, pumps and structures. It does not replace a facility's IPC protocols.