My dad needs help getting off drugs who do i talk to?

i used to smoke weed but my dad helped me stop he got me in a program to stop but then my dad just turns right around and smokes weed himself i found a bong and like five pipes under his bed i want to talk to him but i dont know how what do i do please if you have a answer please contact me my dads life is falling apart my dad lost his house due to weed and is living with my grandparents he works at a bar as a bouncer and a concrete finisher he used to be so happy but now he is always angry or sad please help me