بسم الله الرحمن الرحيم
If a potter kneads the soil with impure water when making the pot, then the use of such a baked pot made with filthy soil will be permissible and wudhu will be correct with the water that is present in it.
أفضل التطبيق العصري على مسائل القدوري
للمفتي محمد أشرف الاشاعتي
Vol.1 Pg.152