I know Mike Butler (Landlording on Autopilot) recommends including in your lease agreements that a service call that is due to an issue that is the tenant's responsibility (and he gives examples of which ones those are) will be charged a service call fee (like 25 bucks) + repair costs. This is supposed to encourage them to fix things themselves, or get them to be more proactive on alerting you.
I've never tried it, because my concern is that tenants would instead just clam up to keep from being charged and I'd end up with a bunch of deferred maintenance nightmares.
But I suppose there might be a kernel of that that you could adapt for your purposes since it's an issue that keeps coming up. Truthfully, though, they live in the unit and you don't. Leaky fixtures are your responsibility (even if you charge them for the fix), but you can't possibly fix them IF THEY DON'T LET YOU KNOW THERE'S A PROBLEM. And water bills because they didn't tell you about a leaky fixture are certainly not your cost to bear.
I think this is more a tenant-training (and possibly tenant screening) issue than a repair issue.