About what? Are there any surviving pre-Roman architectural manuals or treatises? Or other significant sources? (not rhetorical questions, I'm not a professional historian and might be missing something and in any case it would be very interesting to read about them).
> we don’t know
We (well not we... usually only enthusiasts/people working in the area) do of course know a lot. Just quite a bit less than about the Romans. What matters the most here is that Greek/etc. plumbing/sanitary practices have very little exposure in popular history.
Well, it depends on what you mean by "popular" history. Popular, were? I grew up in Greece and I learned early on about the Minoan palaces with running water (and internal heating). As to the sanitary practices of mainland Greeks, I remember this joke, variously starring Aesop or Socrates:
Aesop (or Socraters) goes to the public baths. He takes off his clothes, enters the water, rubs himself, etc, then comes out and says to the official: "that was great. Now, were do I go to get cleaned?".
Greeks had public baths, like the Romans and they were probably as filthy as those of the Romans. I've also seen plenty of archeological evidence of plumbing and sewage in various museums around Athens. IIRC there is a section of the floor in the Akropolis Museum covered by glass so one can see the underlying archeological layers, including the terracotta pipes used to carry water. These may have been from Roman times though, I can't say I remember.
(Theories those pipes carried steam for ancient Greek robots with cogwheel brains have been debunked).
You must be joking.
I am not saying the Romans were the first, but surely we can do better than “of course there were others, but we don’t know”.