The sinks in our home can be a dangerous place for toddlers. As they are learning to become independent, they often want to experiment and play with water, faucets, and sinks. To prevent burns while your toddler washes his hands, consider turning off the hot water to the sink completely. There should be a shutoff valve under the sink.
If you’d still like to have the hot water function on the sink, a mixing valve can help lower the temperature so that it’s only warm, and not too hot to burn sensitive skin. These Sloan Mechanical Mixing Valves have been working great for over a year now. I have them installed at all the sinks that my son uses. It’s a pretty quick installation if you’re handy and should be a quick job for a plumber if you’re not comfortable doing it yourself. My son helped me install them so it doubled as a fun learning process.