First time owner-Black water tank clogged....help!

never had that issue but there is a digest it and you pour 1 pint down the black tank and fill with water and within 24 hrs it will dissolve all solids. I purchase mine from amazon.

Unique Natural Products RV Digest-It Holding Tank Cleaner, 128-Ounce


by Unique Natural Products

then use it after each flush. this is the gal size. Hope this helps.