Cat pee/Crystals in urine

My cat is about 6 years old, and was neutered at the age of 1. I am still having issues with him peeing on my furniture and carpet. I have been through 3 couches in the past 3 years. At first i thought it was because we had adopted a second cat after we had him, so we ended up getting rid of her. Then it started again, so we took him to the vet and found out he had crystals in his urine. He has been on special cat food ever sense. Well, it didn't start getting much better, so awhile later we took him back, and he still had the crystals. Is there anything else we can do to get rid of the crystals to avoid them coming back? It seems every year or so they start to come back.

[opus88]

first of all are you feeding canned food and NOT dry?...this is the biggest contributing factor of urinary tract problems......he doesn't especially need a special diet like what the Vets will sell you....but he does NEED canned food and lots of water.
I have a kitty with the same problem and a change for dry to wet made all the difference.
also encourage him to drink, if need be buy one of those kitty fountains....many cats like the running water and love to lap at it.
and everywhere he has pee'd will need to be cleaned with a special enzyme pet product that removes the scent, not from our noses but from theirs...or he will continue to pee there thinking its a litter box....cats are ruled by their noses.

heres an excellent site to read and understand more about how diet affects the urinary tract of kitty.....please get him transitioned over to a good canned diet asap...

post again if we can help answer anymore questions..good luck to kitty..

http://www.catinfo.org/?link=urinarytracthealth