Essential: Tend not to pour boiling water into a drain In case the pipes are made of PVC, Pex, or CPVC since it might melt the joints (source). Also, watch out In case you have a porcelain sink: don't pour boiling drinking water (or pretty very hot drinking water) directly https://express-page.com/story3884297/the-fact-about-how-to-clean-drains-in-arar-that-no-one-is-suggesting