[Clilmence]

What do you do when you only receive water from watercompanies who purify sewage water? Are you obligatory to check with your watercompany how they purify their water? Should you perform wudu with rain instead, just to make sure?

Treated sewage water

In principal, impure water does not become pure merely by the disappearance of impurity and its traces from the water. This is the case even if the impure water is in a large quantity.[i] Similarly, impure water does not become pure merely by filling a large tank with it, regardless of whether or not traces of impurity are apparent in it.[ii]

Hence, sewage water will not become pure merely due to being treated. Pure water (according to the Shariah) and biologically clean water are two different things.

Impure water becomes pure when it flows with pure water.[iii] Similarly, it becomes pure when it enters a large body of pure water.[iv] Large body of water is that water whose surface size is approximately 23 metres square or more.[v]

In both cases (i.e. whether the impure water flows with pure water, or it enters a large body of pure water), the condition is that after mixing with the water, the smell, taste and colour of the water should be that of normal water. If any of the three qualities of water (i.e. its smell, taste and colour) changes due to impurity, the water will be impure.[vi]

Therefore, if treated sewage water is released into a large body of pure water such as a lake or river, the lake or river water will be pure as long as the smell, taste or colour of the water does not change due to impurity. However, if treated sewage water is released to a small body of pure water, the entire water will become impure regardless of whether or not the smell, taste or colour of the water has been affected by impurity.[vii]

Similarly, since water travelling in pipes is flowing water[viii], if treated sewage water flows in the pipes along with pure water, the mixed water will be pure with the condition that the smell, taste or colour of the water is not affected by impurity. This is the case even if the pure water is less than the treated sewage water.[ix]

Note that impure water does not become pure by flowing with impure water, regardless of whether or not there are traces of impurity in it.[x] To become pure, it must flow with pure water. Therefore, if treated sewage water travels in the pipes by itself, it will not become pure.

Another way in which the treated sewage water can become pure is that after impurities have been removed from the water and the taste, smell and colour of the water returns to that of normal water, pure water is poured in the tank containing the treated sewage water till the water overflows from the tank. As soon as the water overflows from the tank, the entire water in the tank will become pure. This is because the water of the tank will be considered flowing water as soon as it overflows when water is poured in it. This is even if the water that overflows is little. The water that overflows is also pure. This is regardless of whether the water is in a large tank or a small tank.[xi]

The above will apply even if the treated sewage water is in a bucket or a container, i.e. if a bucket or container is filled with treated sewage water and thereafter pure water is poured in it till the water in the bucket or container overflows, the entire water will become pure.[xii] Even the water that overflows and falls down will be pure.[xiii]

Note that all the rulings mentioned above are based on the assumption that when the sewage water leaves the home and travels in the pipes towards the treatment plant, the smell, taste or colour of the water changes due to the impurities in it. If the assumption is wrong, the rulings may be different.[xiv] This is because of two reasons: 1) The water that travels in pipes is considered flowing water. 2) Along with impurity and impure water, sewage water also contains pure water. http://www.askimam.org/fatwa/fatwa.p...b3c19b9c320490