Is it permissible to perform ablution (wudu') with water from a well whose taste and smell have changed due to its proximity to sewage pits, and will the mosque carpets become impure (najis) if people perform ablution with it?

If the taste of well water near sewage disposal wells changes, it is deemed to have lost its purifying quality, and it is not permissible to purify oneself with it for prayer; this is because the presumption of its change due to impurity is considered valid. For purification, one must seek another water source or purify the well by pouring a large quantity of water into it until the trace of impurity disappears, or by drawing out the water until no trace of impurity remains. The Malikis, Shafi'is, and Hanbalis hold that increasing the water purifies a well that has become impure if the change ceases, and this can be achieved by leaving it until the water increases or by pouring pure water into it, while the Malikis permitted drawing out the water or the disappearance of the impurity's trace by any means. As for the ruling on mosque carpets, if a person performs ablution with impure water and enters the mosque with wet feet, the spot where their feet touch the carpet becomes impure. However, if their feet are dry, it does not become impure. When in doubt about a part of the carpet becoming impure, the original state is purity, and it is not obligatory to abandon the mosque for that reason.