Krylon Fusion (plastic paint) as well as the Rustoleum equivalent have been used and tested many times over in the hobby. Main uses have been for DIY filter as well as commercially made canister filter intake/outlets and other PVC products. The key to making sure it is safe is to let it dry and cure completely, often suggested time I have seen is one week to be safe. I would recommend rinsing thoroughly as well. If you're not certain or just want to see others opinions, do a google search you will find that this has been done with success for some time now.
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