Instructions for making a makeshift filter for drinking water using a ceramic Sterasyl or Supersterasyl cartridge.

You'll need:
A cartridge complete with wingnut and seal, a piece of string, a clean empty plastic bottle, bucket or similar.

Tools:
Something to cut the bottle and make a hole in the bottom of it, something to cut the string.

Method:
Cut the neck off the bottle, then make a hole in the bottom of it big enough to accept the thread of the cartridge. Put the cartridge (with the rubber seal on the threaded portion) upside down inside the bottle, poking the thread through the hole and secure it with the wingnut. Make two small holes near the top of the bottle adjacent to each other and tie a length of string through of a convenient length to hang up.

Using the filter:
Use the best source of fresh water you can find. Never use seawater or urine. Rainwater is ideal, flowing water is generally better than stagnant water - take local advice. If the water is muddy and discoloured, allow it to stand if possible to reduce the suspended particles. Pour the water carefully into the bottle around the cartridge and allow it to come out of the end of the cartridge below the bottle. It will take a few minutes to start dripping. Keep the water around the filter topped up for maximum throughput. Never allow contaminated water to splash or run down the outside of the bottle - this will contaminate the product water and compromise it's safety. If water purification tablets are available they can be used to prevent re-contamination of the water by bacteria.

Other ideas:
Depending on the materials available, a large clean bucket could be used which would reduce the need for topping up. Several cartridges could be fitted to increase the throughput. If heavily contaminated water is used the flow may be reduced. Excess particles and sludge can be removed by lightly scrubbing the ceramic to restore the full flow. Good hygiene must be practised to avoid re-contamination of the filtered water.

Deploying the filters effectively:
A cartridge will last for many months - even with heavy use, at least until supplies of clean water are restored. There is no danger of it "running out". Used effectively, one catridge will supply sufficient water for drinking and basic cooking for 6 or 7 people. They should be handed out individually to responsible community members by someone who has read these instructions and studied the diagram overleaf. Appropriate assistance should be given to help set up and commission the filters if necessary.

Feedback:
These filters have been donated by Greens Water Systems. We need feedback and comments from people in the field to make sure future batches can be put to the very best possible use. Call +44 1522 509383 or email: emergencyfilters@water-systems.co.uk