Hi there. We have a dog who is very geriatric! He is quite blind, and just recently he has started to urinate and pass feaces just outside our backdoor rather than finding somewhere in the garden. The biggest problem is the urine which is so strong it makes my children gag. The smell is totally rank and is a major source of embarrassment when people visit. We wash the area with Phenol and hot water but the smell returns within two hours. Can you suggest anything that we can do to deter him from doing his business so close to the back door?