Boiling water is generally safe if you have older, heavy-duty plumbing systems, specifically:
If the sink is full of cold water, boiling water won't work. It will lose its heat the moment it hits the standing water. Bail out the sink first. boiling water down drain
Pour the water directly into the drain opening in two or three stages, allowing the heat to work on the clog for a few seconds between pours. Boiling water is generally safe if you have
Never pour boiling water into a toilet. The extreme temperature difference between the cold porcelain and the boiling water can cause the bowl to crack instantly due to thermal shock. Similarly, thin porcelain or glass sinks can crack if exposed to sudden high heat. 3. P-Trap Seals heavy-duty plumbing systems