| Caveat: I come from the monitoring and control system side, so I've only learned about the actual water treatment part as a side effect from working on monitoring and control systems for it. 1) My understanding is there is very little actual hazard here, provided the pipes are in reasonable shape and there isn't a source of contamination. One example of a source of contamination: dead ends in plumbing (eg, an old branch that's been capped off). The stagnant water can grow bacterial colonies which can then contaminate everything downstream from where the dead end branches off. The residual chlorine can fight this but it's of course better to not have the dead end at all. 2) The problem with the dips is it's not possible to distinguish between the "expected" nightly dips and real problems. For example: do you just ignore all alarms between 3am and 6am? or should that be 7am? Is there another check (+alarm) to be sure the clock is correct (and do you now need a secondary clock source for that) and that DST is respected? Or do you build something very complex that checks against recent flow rates before raising the alarm -- in which case, how do you test that code and ensure it never breaks (keeping in mind it's safety-related and it's very hard to unit test real-world flow meters, chlorine sensors etc). This gets difficult because you might have different plumbers / maintenance people doing things (adding branches, fixing leaks, etc) that might change the physical layout and not even realize there is control software that might be affected by changes. You can add more sensors to try to check for some of these potential conditions but each sensor costs even more money and adds more complexity. A lot of this is really "CYA". If something ever did happen and a resident got sick (or worse) from the water, and it came to light that not only were there alarms every night but they were specifically suppressed, even though that might be a rational decision given the facts, at best, that decision would still be faced with a lot of scrutiny and at worse it could be considered criminally negligent. 3) It's basically not possible to flush the ENTIRE building, because you'd have to open every fixture (every sink, shower, and flush every toilet). In this case, the solenoid dumped water from what was effectively the main line through the building which everything branched from, so from any apartment running the water for maybe a minute would get you fresh water from that main line. So I'd rank this in the middle of what you said: "quality was probably (usually) fine before, definitely more likely to be fine now, and if an alarm goes off at any time it's real". |