Why does your dog pee on the floor after you leave home?

This usually happens to an already house trained dog out of separation anxiety when you leave. Find a book on Dog Training that includes a section on separation anxiety for the best advice.

It could be that you are leaving them alone too long and they just can't hold it. The younger and older dogs may have this problem more often since they do not have full bladder control.

It might be to mark the territory, it may feel like it is in charge when you are gone and it wants to let everyone know that the house belongs to it.

It will not be to "punish" you for leaving, they don't do naughty things in revenge.

They may need a house training refresher course with diligent attention to their bladder habits for a period. This may be needed due to a new scary thing or sound or other change in their environment that is unsettling to them and their routine.

There may have been thunder, a car backfire, fireworks or other loud sounds that scared them while you were gone. It may not have been a problem for them if you had been home to reassure them, but on their own it was just too much to handle. There are special coats for them that really help with this. One brand is called Thunder Shirts.

It may be that they need a medical check up to be sure there is no injury, infection or other medical condition that is causing it.