Hi janmk - what are you washing the beds with? Is it possible the smell is still there and your dog is "marking" it, rather than actually needing to empty his bladder? You could try spraying them with one of the pet-specific cleaners and see if that helps.
If not, how long as he been doing it? Just wondering if there's some sort of trigger. Sorry, not overly helpful really but didn't want you to go unanswered!
I have two dogs. One pees quite often in the beds either in the utility or in the lounge. With a 5 month old I really don't need the hygiene issues or the washing !
I have had her we tested at vets - all clear and tried pheromone plug ins and collar . The other dog is lost since I moved the bed from the lounge and even sat in Lo's car seat . Any ideas how I can stop this behaviour ?