I have to have a plumber in once a year to unclog my kitchen sink drain for the last three years. The last plumber who arrived while I was at work told my adult son that I needed to use muratic acid to clean the grease from my drain pipe. The house was a repossession by a bank and I don't pour grease down the drain or in the garbage disposal. I bought some muratic acid but the bottle does not indicate what strength is safe for pvc pipe. Any ideas or suggestions for this procedure would be greatly appreciated.