Help Cat weeing on sofa

[Lorna5]

My 3 year old indoor cat is weeing on my leather sofa i have tried everything but she's still doing it and i'm getting desperate
I've tried taking her to the vets she had cystitis and crystals but this has been treated with antibiotics and diet, i've put dry food in bowls on the sofa i've thoroughly cleaned the sofa, i change the litter tray daily but still she persists. Yesterday i left the room for ten minutes and she had done it. I have now resorted to shutting her in the kitchen but this means our other cat who is 18 is also shut in the kitchen as she does't like to be alone.
I don't want to have to shut them in all the time but i don't know what else to do. I have even considered re homing but i don't want to lose her and the old cat would be bereft.
Please help

[greenkitty]

How many litter trays do you have? The general rule is 1 per cat plus 1 extra so it might be worth introducing a couple more trays to see if this helps the problem.

[Walesgang]

You could also try a different type of litter

Mine prefer a clumping earth type litter

And make sure trays are cleaned regularly and away from food/water

[Lorna5]

Thank you for the replies have tried all of these new litter trays, they are changed daily now washing sofa with biological powder and white vinegar if all fails will have to keep her in the kitchen which i really dont like doing. Havent tried a different litter yet