Does a washing machine in the USA render Najis clothing Tahir? For example, if one had a wet dream, is it sufficient to put the Najis trousers in the washing machine (mixed with other clothes, and washing detergents, etc.)? Or if I had blood on my t-shirt, can I just wash it in a washing machine to make it Tahir? Or must I place the Najis clothing under water once to get rid of the Najasah, and then once again place it under running water? What is the ruling of Ayatollah Sistani on this?

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Question: In the West, there are many public laundry places in which Muslims and non-Muslims wash their clothes. Is it permissible for us to pray in the clothes washed in such facilities, especially when we have no knowledge whether or not the washing machines are connected to the kurr water2 at some stages of the washing, and whether or not it purifies the clothes in the process of washing?

Answer: There is no problem in praying in those clothes that were pure before washing them [in such facilities] as long as you are not aware that they have become impure. [In other words, what goes in the public washing machine as pure comes out as pure unless you are sure that it has become impure.]
Similarly, [you can pray in] the impure clothes [that were washed in the public laundry machines] provided that you are reassured:
– that the impure element, if any, has been washed away;
– that the pure water covered the entire impure area twice (if it had become impure by urine and even if the water was connected to kurr source as an obligatory precaution) or just once (if it had become impure by other elements);
– and that the water was removed from the clothes by wringing or other similar method [i.e., spinning of the machine] if it was qalil.
However, if you are not sure and just have conjecture that the garment has been purified as per religious requirement, the previously impure garment will still be considered impure and praying in it would not be valid.

https://www.sistani.org/english/qa/search/34299/