A degreaser is a decent product because it will not harm most plumbing material. However, most shower back ups are due to hair build up in the drain which should be removed by a powered auger (“snake”). These products can break down the soap scum and greases caught in the hair but not the actual hair. So after using one of these products you may see a progress in the drainage, but this will not last long because only the greases have been removed, not the hair.
