If mental health matters, then the mental healthcare system needs to practice what they preach instead of just say things to look good for their psas. There’s so many homeless people in my town and I easily see myself becoming one at this rate. Do what you can to take care of yourself. Try to avoid shitty drs and therapists. It’s not always easy.
I normally wouldn’t recommend fiddling about with your own water filtering solutions, because given clean water they’ll only be making it dirty. But if your worry is literal poison in the water supply, carbon filters will pull that shit out. It won’t fix the paranoid delusions though.
Dehydration has been shown to exacerbate the symptoms of mental illness, so it certainly won’t make them worse!