system
Given the following post, respond as if you're commenting on Reddit:
human
[LOTR] How does the plumbing work in an underground Dwarven Kingdom?

Following on from thinkaboutfun's relatively sensible question regarding smells: 

Regards the renouned underground caverns in which Dwarves live, it seems that they'd be skilled at creating vehtinilation, but not everything can be carried away on the wind. 

Where does Dwarven excrement go? 

Is there just a massive cesspit at the bottom of their home, and as they go deeper, do they have to dig another, or do they - urgh - extend the original by digging beneath and letting the previous accumulations drain through? 

Do they make use of these chambers? Are they like ants, and use their waste as an agricultural based recycling?  After a hundred years are the upper levels then renovated into living spaces?

Or do they have a disgusting pulley system of dwarven shit and piss to be deposited outside of their homes in some sort of sloppy fecal volcano? 

Have these fecal volcano holes, these orifices of dwarven cities, these oozing shitholes of the collective Dwarven residents, ever been used as an entry point for goblin infiltrators? 

DID BILBO ENTER EREBOR THROUGH THE SHITTER?
gpt
Have you ever noticed that, whenever dwarves "delve too deep", the creatures that emerge from the black caverns beneath the world are always in a seriously grumpy mood?

Yeah, this is pretty much why.