I tried it today....and it works great!
I just put my pvc parts in and let them simmer away for an hour. I'm not sure if they needed that long, but that's how long I left them in.
Just be sure to rinse them in soapy water after your're finished (I rinsed mine in clean tap water until it ran clear, then noticed that when I towel dried them, quite a bit of black dye came off on the towel. After I cleaned them in soapy water, I rinsed them extra well to be sure I got all the soap out, and no more dye came off on the towel.
They're back in the tank now, and look great....I mean, they're practically invisible against my black background. Can something that's invisible look great?