You have a partial blockage downstream of where the shower drain & the sink drain join into one pipe. You could try a thin plumber's snake, or add some drain cleaner, some bleach, or vinegar. About a liter of vinegar is the safest and should work well enough.
Davis
(davisbigelow.blogspot.com)
To prevent a bathroom sink overflow drain from getting clogged, regularly clean the drain by using a mixture of baking soda and vinegar, and avoid pouring grease, hair, or other debris down the drain. Additionally, use a drain strainer to catch any large particles before they go down the drain.
If your bathroom sink overflows, first turn off the water supply to stop the overflow. Then, use towels or a wet vacuum to clean up the water. Check for any clogs in the drain and clear them if necessary. If the issue persists, consider calling a plumber for further assistance.
A typical bathroom sink uses around 1.5 to 2.5 gallons of water per minute when the faucet is running.
Yes, they work in either.
Common issues with a bathroom sink drain with overflow include clogs, leaks, and slow drainage. To address these issues, you can use a plunger or drain snake to clear clogs, tighten loose connections to stop leaks, and use a mixture of baking soda and vinegar followed by hot water to improve drainage. If these methods don't work, you may need to call a plumber for further assistance.
In my experience, I would say no. Several reasons can prevent the overflow from working. Since the overflow of the sink is rarely used it has a tendency to be blocked at the lower portion where the sink joins the drain pipe. During normal use and over years the holes in the sink drain at the point where the overflow and drain pipe meets has a tendency to clog making the overflow drain slowly. You can notice this when your sink drains with a "gulping" sound. You can test the overflow drain and see how obstructed it is, but do it slowly and do not turn on the faucets on full.
I found someone's Medabon on the bathroom sink.
use slicone glue
To prevent a sink overflow and keep your sink clean, avoid letting water run continuously while using the sink, regularly clean out debris from the drain, and use a sink strainer to catch food particles. Additionally, avoid pouring grease or oil down the drain, as it can cause clogs.
To effectively clean the sink overflow hole and prevent clogs, you can use a mixture of baking soda and vinegar to break down any buildup. Pour the mixture down the overflow hole and let it sit for a few minutes before rinsing with hot water. You can also use a pipe brush or a toothbrush to scrub the area gently. Regularly cleaning the overflow hole will help maintain proper drainage in your sink.
See the link below.
You could use a bathroom and use hot water :)