Tap water smells musty

Why does the water coming from the faucet smell like a riddle? Strangely, it is only at one faucet, the one in the bathroom. At all other water points, it does not happen. My question is whether something like that can also be caused by the faucet. There are plastic pipes everywhere. The water from the tap smells when you bring your nose close and drink water directly from the tap. I also thought it was the drain at first, but then it would always smell.

Drainage, I thought at first as well, but then it would always smell

No, only when it gets wet. Just take a glass with you into the kitchen and see if it still smells then. Then you'll know for sure if it's the water.

No, only when it gets wet. Just take a glass into the kitchen and see if it still smells then. Then you'll definitely know if it's the water.

Or the other way around: Water from the kitchen into the bathroom drain

I’m trying, but I don’t think it’s coming from the drain

This is new construction, I do not know exactly how the pipes run off the top of my head

Especially with new construction, you should have photos from the construction phase, right?

Especially with new constructions, shouldn't there be photos from the construction phase?

...and plans are also not uncommon