Clean the drain with salt and boiling water
Have used a drain cleaner (granules from the supermarket) for our sink in the kitchen, since it was a little bad. Guys, keep your hands off that stuff. That does not do anything, but everything clogs everything.
We worked exactly according to instructions. Unfortunately, the drain cleaner worked like concrete and sealed the entire runoff. In the end we had to disassemble the drain and scratch out the "concrete".
To save a lot of work and money, we recommend all, take normal salt and tilt about 1/2 cup full of it in the drain and then boiling water afterwards. Makes the drain super free.
