A small one.What PLC's would be used for home heating system?
A bigger one.What PLC's would be used for a water waste plant?
Homework ?
Short answer is anyone you have can be used for either
Home heating: An Allen Bradley MaxiLogix 1970-L212 with the double column compensatory and the quad-syncro digital outputs.
Water/Waste water: Another Allen Bradly, the FuzzyLogix 3214-S1422 and depending on the area of the world you might want to add the reverse polarity thermo-stator flange boot (just to be on the safe side).
I'd go with a retroencabulator that is tuned for the modial interaction of magneto reluctance AND capacitive reactance.
https://www.youtube.com/watch?v=NpnEiOOfu1Q
I was also going to suggest the median earth tilt erector corrector, that little blue module.
you can’t tell people to stop pooping for a week.