I had a thread recently about one of my girls peeing/pooing in the house but not in the litter tray.
The thread is here www.mumsnet.com/Talk/the_litter_tray/2350165-Cat-has-unhousetrained-herself
It was suggested that maybe it was arthritis but since my post, the girls spent a week at my parents whilst we were on holiday and had no issues using the trays.
Since returning home, she's started doing it again. Almost always by the front door. We've put plastic sheeting down by the door and she wees on that but also I think in other parts of the hall. The whole hallway and a lot of the house smells of cat wee and it's just awful.
I'm thinking it's probably territory related, any tips on how to get her to use the trays again, or even better start peeing outside like she used to?