FAQs – Frequently Asked Questions
1. Does the BioSand Filter (BSF) kill all the bacteria?
Typically the BSF will remove over 90% of bacteria if installed and used properly. Often, the amount of bacteria left alive will not be enough to make someone sick. However, disinfection using chlorine, or solar rays from the sun, is recommended to remove any remaining bacteria
2. Will the BioSand Filter (BSF) take out parasites?
Yes, typically 100% of parasites are removed if the BSF is properly installed and used. It is important to note that most parasites are highly resistant to chlorine disinfection, so the best way to treat drinking water for parasites is to filter them out.
3. Will the BioSand Filter (BSF) remove the dirt in the water?
Yes, the BSF removes over 95% of the dirt (suspended solids or turbidity) in the water. However, if the water is very dirty (over 70 – 100 NTU-turbidity units) the filter will need to be cleaned frequently which will make it less effective. If the water is very dirty, it should be allowed to settle until it is clear and/or filtered through a fine-woven cloth (folded over many times) to remove most of the dirt before pouring it through the filter.
4. Why do I need to add chlorine to the filtered water? Isn’t the filter enough?
The filter removes most, but not all, harmful bugs in the water, and all of the parasites that have a high resistance to chlorine. Adding chlorine to filtered water will kill the bacteria that survived the filter and prevent recontamination of the water. Without chlorination, those people with low immune systems – especially children under 5 years – can still become sick. Finally, if the raw water is very dangerously polluted, further treatment by chlorine after filtering is necessary.
5. How do I chlorinate?
Dirty water should always be filtered before adding chlorine. Place the chlorine (or bleach) in the storage container that the filtered water runs into. It is recommended to add enough chlorine to kill all remaining bacteria in the water and have a little left over to continue to protect the water. It is difficult to estimate how much chlorine to add to water because it depends on what is in the water and the concentration of the chlorine solution (bleach is usually around 5%). Typically, it is recommended to add between 1 to 5 drops of bleach to every litre of water (or up to one teaspoon for each gallon) and allow 30 minutes before drinking. When there is a very slight chlorine taste and smell then sufficient chlorine has been added. You may add a little less next time to reduce the smell and taste so that people continue to chlorinate their water.
6. How do I check the turbidity of the water to see if it is below 70 – 100 NTU?
Fill a 2 litre plastic bottle with the water. Look down through the water in the bottle. If you can see printing the water is less than 70 - 100 NTU and can be used directly in the filter. If the water is too dirty see Question #3.
7. Does the BSF remove salt from sea water? Pesticides, industrial contaminants or other chemicals?
The BSF does not remove the salt in sea water. Nor does it remove chemical contaminants such as pesticides, industrial contaminants, or fluoride dissolved in the water. Some modifications of the filter are possible to help remove arsenic. Chemical and other contaminants can only be determined through water testing.
8. What does a good (well installed and maintained) BioSand Filter (BSF) look like?
Location: Protected from the weather (dust & wind), birds, animals and insects
Indoors: Placing the biosand filter indoors is preferred
Level: Filter should be placed on a level spot - even floor, not slanted, no bumps
No leaks or cracks: Drips of water or wet spots under the filter will indicate a leak
Lid: Clean on the inside and outside, tight fitting but not sealed
Diffuser: Clean regularly; sand under diffuser should be level and smooth
Smooth and Level: The surface of the sand should be 5 cm (2") below the water level
9. What is the best way to use a filter? How can I make it work better?
Try to get water from the best possible source. Always use the same source if possible. If water is very Ensure the receiving container is clean. Slowly pour contents of bucket into filter, without letting the sediments enter filter, and then replace
The water is measured during the pause period
dirty allow the water to settle for 24 hours then pour the clear water through a fine-woven cloth
(folded many times).
Add 1 to 5 drops of bleach for each litre (or up to 1 teaspoon per gallon) – for example, if the container
is 20 litres then add at least 20 drops.
Remove the filter lid
the lid.
When filtration is complete, cover receiving container.
Repeat process at least once a day
Clean the spout daily.
Do not store food on the diffuser plate
Keep animals away from the spout and filtered water
The BSF will be helpful in cleaning any water except sea water or chemically contaminated water.
Always usethe cleanest source water available and try to use the same source if possible
11. What are the mistakes often made by new users of the BioSand Filter (BSF)?
1. New users want to attach a valve on the spout. This keeps the water level too high and prevents
oxygen from reaching the bio-layer
2. New users ‘swirl & dump’ the filter too often which reduces the effectiveness of the bio-layer
3. New users add chlorine to the water that goes into the filter instead of adding chlorine to the container
that receives the filtered water. Adding chlorine into the top of the filter will kill the bio-layer and reduce
the effectiveness of the filter.
4. New users will often not allow the dirt in the water to settle before pouring the water through the filter
5. New users will often not use the best source of water because it is inconvenient.
6. New users will place the filter outdoors rather than indoors. This increases the risk of recontaminating
7. New users will often put food in the filter as it is cooler in the reservoir
8. Often don’t use the water for all of their needs; bathing, dishwashing, cooking and drinking
9. New users will often use a dipper or scoop to take the water out of the storage container.
This can cause recontamination. The water should be poured out of the storage container.
12. What does the bio-layer look like?
The bio-layer is not visible except possibly as a slight discolouration at the top 5 – 10 cm of the sand.
13. Does anything from the filter dissolve into the water and cause a possible health risk?
No, the cement, sand and bio-layer will by themselves not cause any health risk.
However, if the sand is brought from a river, stream or lake area, it may be contaminated with bacteria
and must be cleaned (washed then dried under the sun or heated) to remove any possible health risk.
Also, the pipe inside the filter including the spout should be disinfected when the filter is installed.
14. How should water from the filter be stored?
The water should be stored in a clean, closed container which allows the water to be removed by pouring
Also, the water should be disinfected using chlorine to prevent recontamination during storage.
15. What if the flow from the filter is very slow?
This means that the top layer of sand in the filter is plugged with dirt. This material should be
removed using the ‘swirl & dump’ technique:
16. How often do I change the sand?
The sand should never need to be changed. It is cleaned by the ‘swirl & dump’ technique described above.
17. How high should the water be above the sand?
The top of the water, during the pause period (the period when no water is flowing through the filter), should be
5cm above the top of the sand. This allows the oxygen in the air to keep the bio-layer alive. If the sand is less
than 5 cm, remove some sand, if it is greater than 5 cm then clean sand should be added.
18. How often can I run water through the filter?
The filter can be used continually. You can add water anytime there is sufficient room in the top of the filter,
although normally the filter is not run at night.
19. What do I do if my filter dries out?
This may happen if the filter is left unused for a long period of time or if there is a leak. The water level must be
established by filling the filter through the pipe (using the spout) so that the water rises from the bottom up
preventing air from becoming trapped in the sand. This can be accomplished in the same way that the initial
sanitation of the pipe is done.
20. What is the optimim water flow rate?
The optimim flow rate when the reservoir is 1/2 full is 0.4 litres per minute or 1 litre per 150 seconds
Friends Who Care Canada
63 Sunlake Way ZSE
Calgary, AB T2X 3E4 Canada
Phone 1-403-278-2780
fwc@friendswhocare.ca