I was originally using cat San non clumping litter which did a good job of reducing odour but it meant that I had to completely empty and clean the tray at least once a week. So I bought some cheap clumping litter to see if that would be any good and I absolutely love it. I love that I'm scooping out all of the urine and poop so all I need to do is top up the tray and completely refresh it every now and then. However, because it's a cheap litter, it uses so much to clump. My sister said that she mixes in a walnut shell litter with hers as it uses less to clump. She's in the US though. I just wondered what clumping litter people here used and why?