Do you know what type of crystals (eg. Struuvite or calcium oxalyte)? Very often, the problem when crystals occur is diet - and it can often then be solved with dietary change (which may include changing water source).
One other thing to bear in mind is lifestyle. Crystals can only form in the urine when the urine is concentrated. In simple terms that means that avoiding letting the urine become concentrated will help avoid crystals. That in turn means higher water intake and potty stops more often (you don't want a dog with crystal problems eating too much dry food or being asked to hold their bladder for long periods).
