Muriatic pool acid works the best of anything. But,the fins on the outside of the coil can also get plugged with mud and then the heat transfer cannot occur.: Does anyone know what can be used to clean the deposits out of the inside of a coil.A friend had it done professionally years ago-I cant find anyone to do it.Everyone wants to replace the coil.House is only 9 years old and second coil is already working poorly.Anyone know of a product/brand that will work? Thanks-Matt