How can a house and its contents be purified after being exposed to water spray from a fountain that contained a dog, knowing the difficulty of washing everything seven times, one of them with earth?

The presence of a dog in a pond or fountain does not affect the purity of the water. Abundant water, such as in ponds and fountains, does not become impure if an impurity falls into it unless one of its characteristics (color, taste, or smell) changes. This is supported by the Hadith (definition) of Bi'r Buda'ah. The fundamental principle is that water is pure unless its impurity is certain due to a change. Therefore, clothes do not need to be washed from fountain spray unless its impurity is certain, and one must be wary of obsessive doubts.