Siting and Installing Emergency Water Tanks: A Field Checklist

Tony Miller

Oct 8

8 min read

Emergency water tank installation succeeds or fails on the site, not the kit. Pick ground that is level, firm, high enough to feed tapstands by gravity and well drained. Then a 45 m³ Oxfam steel tank takes two to four hours to erect, per Oxfam's own manual.

Most tank failures we hear about from the field are site failures: a bladder that rolled, an onion tank that slumped, a steel tank undermined by run-off. This checklist follows Oxfam's published erection manual, adds what Juba-based supply experience says about the order of work, and takes a clear view on which mistakes cost the most.

How do you choose the site for an emergency water tank?

Put the tank on high ground, close to the people it serves, on firm and level soil that will not flood. Oxfam's manual says tanks used for storage or treatment should be sited on high ground so water reaches collection points by gravity, and that proposed locations should be well drained and not likely to flood, with a place identified for overflow and wastewater.

Run through six checks before anyone unpacks a box:

Gravity head. Oxfam's 10 m³ bladder tank page says the tank should sit 1.5 m above the tapstands for sufficient head. The erection section of the manual is more lenient and says at least 1 m. Design for 1.5 m and treat 1 m as the floor.
Distance to users. Where water comes from a source 1 km or more away, the manual advises siting storage as close as possible to the population, because the pipes serving people must be larger to cope with peak demand.
Trees. Keep well clear. Roots, falling branches and leaves are the obvious problems; canopy drip also brings living organisms, per the same manual.
Truck access. If the tank will be filled by trucking, confirm the truck can reach it, or that you have a pump and enough pipe to empty the truck.
Drainage and overflow. Decide where overflow and washout water go before the tank goes up. Oxfam advises a 2 to 3 m hose on the overflow outlet to discharge away from the tank base.
Land, security and population movement. A level survey for large systems, and a "simple look around" for bladders, are both in the manual. Land ownership and security belong in the same visit.

Our view: the site visit is the cheapest hour in the project. Do it with the person who will hand the tank over, not only with the person who will build it.

How big should the tank installation be?

Size storage to one day of supply, then check it against peak demand and treatment needs. The Oxfam manual bases storage on one day's supply at the Sphere figure of 15 litres per person per day, dropping to a minimum of 5 litres per person per day for drinking and food preparation where safe nearby sources cover washing. Sphere's basic water needs are 7.5 to 15 litres per person per day.

The manual also tells designers to assume demand peaks around dawn and before dusk, roughly half of daily demand in each, and that long queues all day signal an under-built system.

Worked example (our arithmetic, not a sourced figure): a settlement of 5,000 people at 15 litres per person per day needs 75 m³ of storage for one day. That is one T70 plus a T11, or a T45 and a T45, or a T95. Our companion piece on how much water storage a camp needs takes the sizing question further.

Which tank goes where: steel, bladder or onion?

Use bladder and onion tanks to start up fast and steel tanks to hold a site for months. Oxfam describes its rapid response kits as a start-up package where populations are likely to be highly mobile and says they are not suited to anything but short-term supply, while the steel tanks are durable enough to last several years but not deployable in a few hours.

The published dimensions, from that same manual:

T11 steel tank: 11 m³, 2.3 m high, 2.6 m diameter. Suits a group of 500 to 1,000 people in temporary accommodation such as hospitals or feeding centres.
T45, T70, T95 steel tanks: 45, 70 and 95 m³, 1.5 m, 2.3 m and 3.0 m high, all about 6.4 m in diameter.
10 m³ bladder tank: erected on a marked area of 4.5 m by 3 m. Set-up typically takes half an hour.
30 m³ onion tank: needs a 6.5 m diameter circle marked out.

Oxfam's supply centre lists the steel tank kits in 11, 45, 70 and 95 m³ sizes, with PVC or reinforced rubber (EPDM) liner options. The EPDM liner is offered for sedimentation and flocculation use, per the T70 kit page. Our comparison of onion and bladder tanks for South Sudan covers the rapid-deployment choice in more depth.

How do you prepare the base for an Oxfam steel tank?

You need a cleared, level circle, a shallow trench for the bottom ring, and a smooth or sand-cushioned floor. The manual's sequence for a tank placed directly on the ground:

Mark a circle of 4.2 m radius with stick and string and clear all vegetation, roots, boulders and stones.
If you must cut or fill to get a horizontal surface, compact the fill well and protect it from erosion.
Mark a 3.2 m radius circle and dig a narrow trench about 50 mm deep for the bottom ring. The manual says this stops the liner being forced under the rings.
Spread sand up to 50 mm deep to cushion the liner. If there is no sand, make sure the ground is smooth and free of sharp projections.

Oxfam's tank-based products need no purpose-built foundation: the Butyl Products tank has no base structure and can be erected on any area of flat ground cleared of debris. That is a statement about the base structure, not permission to skip compaction. Soft ground is where steel tanks get into trouble. In black cotton soils or other soft ground, the manual calls it inadvisable to erect tanks taller than 2.3 m without stringent precautions, such as a gravel or concrete foundation ring, extra guy ropes or substantial earth banking. In practice that makes the T95 a poor choice on soft soil unless you can build the foundation.

Where you want more gravity head, build a platform. The manual allows an earth platform with sides inclined at no more than 45 degrees and at least 1 m of working space between the edge of the sacks and the tank sheets. Oxfam's 8.3 m plinth kit for T45, T70 and T95 tanks is dug in about 10 cm, filled in layers compacted every 15 cm, kept to a total height of 1.5 m at most, and should not sit on earth types that swell when wet.

How do you erect the tank and fit the liner?

Work in pairs, bolt loosely until the rings are complete, and protect the liner from everything. The manual puts a 45 m³ tank at two to four hours to erect, and these are the points that cause damage when rushed:

Never erect in wind. Even in calm conditions, no tank should be left empty without guy ropes to stabilise it.
Bolt heads face inside, laps staggered. Check each joint with a spirit level after the first ring, and tighten bolts only when two rings are complete.
Smooth the inside. Flatten dents and sharp edges, then tape the joints between sheets to protect the liner.
Keep oil away from the liner. No petroleum products on or near it. The manual warns they dissolve the liner and contaminate the water.
Clean feet and hands. Liner handlers work barefoot or in clean rubber soles.
Plan the outlets. Typically one hole serves as the bottom outlet and one as the top overflow, with the remaining hole for inlet or washout. Check the liner seams do not coincide with holes.
For T70 and T95, use a step ladder or scaffold, and lift the liner using rope handlers and a platform at about half the tank height.

What do you do the moment the tank is built?

Fill it, restrain it, roof it and fence it. The manual says a finished steel tank should be filled as soon as possible to stabilise it against the elements and to check for leaks, and that nearly empty tanks without restraint have been blown away in the past.

Restrain. Tie ten guy ropes to the eye bolts and peg them down, or bank soil against the outside to one third of the tank height.
Roof. The roof keeps dust, rain and debris out, protects the liner from sun and stops wind lifting the liner in an empty tank. Keep the roof in use at all times.
Fence and drain. Fence installations against unauthorised people, children and animals, and dig a drainage channel outside the fence to divert surface run-off from heavy rain.
Bladders and onions. Fill until the surface is firm when slapped, per the manual, and do not walk on an empty tank in shoes. The 10 m³ bladder ships with a groundsheet and needs reasonably level ground or it will roll when filled, while Oxfam's 10 m³ onion tank page warns that an unlevel onion tank will spill and collapse when filled.

Fill-time is also when chlorination planning matters, because water stored in a tank is only as safe as its residual. In South Sudan refugee camps, 40 to 58 per cent of households collecting from chlorinated tapstands had no detectable residual in stored household water, per the Bulletin of the World Health Organization.

Who runs the tank after handover?

Name the operator before the tank is full. Oxfam's own installation training covers operating and maintaining the tank and handing it over to a third party such as a local organisation, camp manager or utility, and liner repair. Mechanical damage to the liner is the only likely operating problem, according to the manual, and it needs the tank drained and a patch applied to perfectly dry rubber. Keep a repair kit in the site store, not in the warehouse.

Frequently asked questions

How long does it take to install an Oxfam tank?

Oxfam's manual gives two to four hours for a steel tank and about half an hour for rapid response PVC bladder and onion tanks. That excludes site clearing, platform building and commissioning.

Does an Oxfam tank need a concrete base?

No. The Butyl Products tank has no base structure and can be erected on flat ground cleared of debris. A concrete slab base needs the anchor bolt kit, per the T45 kit page, and soft ground may need a gravel or concrete ring for taller tanks.

How high above the tapstand should the tank be?

At least 1 m, per the erection section of Oxfam's manual, and 1.5 m, per Oxfam's bladder tank page. Design for 1.5 m where the site allows.

How big a tank does a camp need?

Enough for one day of supply at about 15 litres per person per day, per the Oxfam manual's Sphere-based sizing. A 70 m³ tank covers roughly 4,700 people at that rate (our arithmetic).

Can the tank be filled and used straight away?

Fill it promptly to stabilise and leak-test it, but the manual's commissioning guidance does not replace disinfection and residual checks for drinking water. Treat the tank as part of the water treatment system.