Bathtub drain odor problem

Good day,

our bathroom was recently renovated, and during this a plumber replaced the drain overflow fitting. After about four months, we have now noticed the following problem: a strong, unpleasant smell (feces) is coming from the bathtub.

The bathtub is used only rarely, about once every two weeks.

What could be the cause, and how can this problem be solved?

Thank you very much

Exactly that, the rare use. Try pouring water into the drain and repeat that for the next few days.....and observe or smell.

Shower on the ground floor here too. I pour water down the drain every few weeks. Alternatively, I was told about oil. It doesn’t evaporate that quickly.

Shower on the ground floor for us too. Every few weeks I put water into the drain. Alternatively, I was told oil. It does not evaporate as quickly.

The problem is different. The water disappears because it is pulled out by the suction of the air. However, this happens even faster with oil because it is lighter.

But in general, oil has no place in wastewater.

We will then try to pour the water into the drain more often. Let's see. Thank you.

The problem is different. The water disappears because it is pulled out by the suction of the air. However, this happens even faster with oil because it is lighter. But in general, oil has no place in wastewater.

Hajoo then one could just connect a vacuum cleaner.. I believe more in evaporation than suction. By the way, when you wash your dirty dishes, what do you do with the frying fat and oil?