Was a bit hesitant to buy this after seeing some of the reviews, but having tried every drain cleaner on the market in the past three months and still having a shower that drained away so slowly it was like standing in a paddling pool, I bought two bottles. Because the blockage was so bad, I used the whole of the first bottle, left it for 24 hours and this morning for the first time in months the water just ran away down the plughole, no problem. I can't recommend this highly enough. I am purchasing a couple to have on standby but hopefully won't need them. It is anamazing product.