Hello,Customerand welcome to Just Answer.
I'm so sorry Felix is having this problem and I completely understand your frustration.
First I would suggest not leaving anything on the floor in the laundry room, like dirty laundry or a laundry basket, as these things are attractive to him and it has become a habit to urinate in these places. Cleaning the floor with an enzyme based cleaner like Nature's MIracle, Zero Odor or Urine Off, if available in your area, is much easier than getting the smell out of the clothes; however, Nature's Miracle does make a laundry detergent that might help with that problem. It's important to clean the areas where Felix has soiled so that he doesn't smell his own urine and choose to return there.
Even though he has been checked out by the vet and did have crystals at one time, he still may have a problem with crystals, a urinary tract infection or inflammation causing discomfort, and that's why he's urinating in places other than his box. He should be eating a diet that minimizes crystal formation like Hill's s/o or Royal Canin s/o. These are sold only by vets. Also, make sure he's drinking a sufficient amount of water and being fed canned food only, as dry food encourages urinary problems in male cats.
Crystals can clump together and cause a urethral blockage which is a medical emergency, so watch for symptoms of that, like pain, frequency and/or not producing any urine at all, or just a little bit at a time. If this is going on for such a long time, he could have chronic interstitial cystitis or inflammation of the urethra and/or bladder. Here is more information: CLICK
If the litterbox in the laundry room is the only one you have, try adding a second one in a different location and this should help, as cats like to have a choice. Also, try adding a litter called Cat Attract to his regular litter and this should encourage him to return to his litterbox because it contains herbal attractants. You can find this litter in most pet supply stores.
Try a cat appeasing pheromone called Feliway, which helps with inappropriate elimination and also helps reduce stress. If you've had any changes in your household recently, like renovations/construction, painting, new furniture, changes in your routines, etc., this can all contribute to stress/anxiety in cats, as they are creatures of habit.
Here is more information on Feliway
I know you're located in Canada, so if they don't carry Feliway, look for any 'cat appeasing pheromone' in the pet supply store. It comes in both a spray and plug in diffuser which resembles a plug in air freshener, but has no scent to humans. You can spray feliway in the areas he's been soiling and this will make him think he has already 'marked' there (wait for it to dry completely--about 20 minutes--before letting him in the area).
I hope you found my suggestions helpful and if so, please take a moment to rate my answer positively and provide positive feedback. Thank you!
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, and I will be glad to continue our conversation.
I hope all will be well with Felix!