Estimating NaDCC Quantities for Shared Water Points in Temporary Shelters

The amount of NaDCC (sodium dichloroisocyanurate) you need for a temporary shelter depends on three variables: the number of people using each shared water point, the daily water volume drawn, and the target free chlorine residual at point of use. A practical starting figure is roughly 1 to 2 NaDCC tablets (typically 3.3 g or 670 mg available chlorine each, depending on product form) per 20 litres of water, dosed to achieve 0.5 mg/L free chlorine after a minimum 30-minute contact time. From that baseline, multiply by daily demand, the number of water points, and the planned supply period, then add a 15–25 % buffer for losses, breakage, and population fluctuation.

Why Shared Water Points Change the Calculation

Shared water points serve multiple households or family groups from a single tap, standpipe, or collection container. Unlike individual household dosing, a shared point must treat a larger, variable volume and account for irregular draw patterns—peak use in the morning and evening, lower use overnight. This means:

• Total daily volume per point can be several times higher than per-household use.
• Chlorine demand increases with turbidity and organic load from many users.
• Residual must be verified at the tap, not just at the storage container, because recontamination can occur in shared distribution lines or at the point itself.

Planning therefore requires treating each shared point as its own dosing unit rather than scaling a per-person household figure linearly across the whole shelter.

Step-by-Step Supply Calculation

1. Define population and water demand per point

Identify how many people draw water from each shared point. Emergency planning commonly uses 15–20 litres per person per day for drinking, cooking, and basic hygiene. A shared point serving 50 people may need to treat 750–1,000 litres daily. Confirm whether the point also serves adjacent shelters or transit populations, because under-counting leads to under-supply.

2. Select the NaDCC product form and dose

NaDCC is available as tablets, granules, or powder. Tablets are the most common format for point-of-use treatment in shelters because they are pre-measured and reduce handling errors. Verify the available chlorine content per tablet or per gram of granules—this is distinct from the total tablet mass. For example, a 3.3 g NaDCC dihydrate tablet typically delivers approximately 60 % available chlorine by mass, or roughly 2 g of available chlorine per tablet. Confirm the exact specification from the manufacturer’s technical data sheet before calculating, because “NaDCC” alone does not define the dose.

Standard guidance for humanitarian emergency water treatment calls for a target free chlorine residual of 0.2–0.5 mg/L at point of use. At the dosing container, aim slightly higher (0.5–1.0 mg/L) to compensate for demand and contact time. Exact dose depends on source water quality; turbid water consumes more chlorine. Pre-filtering through cloth or a simple sediment filter reduces demand and NaDCC consumption.

3. Calculate daily NaDCC need per point

Use the formula:

Daily tablets (or grams) = (Daily volume in litres × Target dose in mg/L) ÷ (Available chlorine per tablet or per gram in mg)

Example: 800 litres/day × 0.5 mg/L target = 400 mg of available chlorine needed per day. If each tablet provides 670 mg available chlorine, one tablet treats roughly 1,340 litres at that dose—so one tablet per day covers 800 litres with margin. Adjust upward if water is visibly dirty or if you must maintain residual after 30 minutes in a warm climate.

4. Scale across all shared points and the supply period

Multiply the per-point daily requirement by the number of shared water points, then by the number of days you must cover without resupply. A shelter with four shared points, each serving 60 people, needing 30 days of autonomous supply, would require:

If you use granules instead, convert using the same available-chlorine principle and verify scoop or measuring device accuracy.

Storage and Handling Considerations in a Shelter Environment

NaDCC is sensitive to moisture, heat, and direct sunlight. In a temporary shelter context:

• Keep tablets and granules in sealed, opaque containers that can be opened and closed quickly.
• Store away from food, fuel, and acidic substances—contact with acids releases chlorine gas.
• Do not pre-dissolve large quantities of NaDCC in water for extended periods; prepared solutions lose potency faster than dry product. Prepare fresh solution daily or per shift.

Label all containers clearly with the chemical name, concentration, and hazard warnings. Only trained persons should handle bulk NaDCC. Provide basic personal protection—gloves and eye protection—for anyone preparing stock solutions at shared points.

Accounting for Variable Demand and Resupply Gaps

Population in temporary shelters shifts. New arrivals, departures, and consolidation of water points change daily volumes mid-planning cycle. Build in a review checkpoint—ideally every 7–10 days—where you measure actual draw volume and residual chlorine at each point, then adjust the remaining supply forecast. If a point begins serving twice its original population, double the allocated NaDCC immediately rather than waiting for the next scheduled delivery.

Logistics teams should treat NaDCC as a consumable with a defined shelf life (confirm the expiry from the manufacturer; typically 2–3 years for sealed tablets, shorter once opened). Do not plan supply solely on the basis of initial population counts without a mid-cycle review.

Quality Verification at Shared Points

Even with correct dosing, shared water points can fall below target residual if demand is high or if users bypass the treatment container. Provide a simple chlorine test method—such as colorimetric test strips or a DPD liquid kit—at each shared point so that a shelter hygiene promoter can verify residual daily. If residual is consistently below 0.2 mg/L at point of use, increase dose or address source water quality before increasing NaDCC volume indiscriminately.

Common Planning Errors to Avoid

• Using per-household dose for a shared point: shared points aggregate demand and recontamination risk; dose per litre, not per household.
• Ignoring contact time: if users draw water immediately after dosing, residual will read low even though the dose was correct. Design the point so water sits for at least 30 minutes.
• Confusing NaDCC mass with available chlorine: a 3.3 g tablet is not 3.3 g of chlorine; use the available-chlorine figure from the product data sheet.
• Neglecting the buffer: broken tablets, moisture damage, and population spikes require a safety margin, not a bare minimum.

If you are confirming NaDCC specifications, supply volumes, or formulation options for a specific shelter deployment, share your estimated daily volume per shared point, the number of points, and your target supply duration so we can help you finalise the quantities.