High Rise Potable Water Systems (& waste system) - How they work

[lowp]

I would like to understand better some details on how the high rise water systems work in Bangkok and have a few other related questions as well. Most buildings have a ground level system that pumps water to a huge tank on the roof and then there is a rotation of user-side pumps with a pressurized cylinder/bladder to even out the flow between pump spin ups.

Our building has about 5 metered lines from the street that goes I assume, to a pump housed somewhere with riser pipes to the roof tank. With a 50 story building, are there one way valves located in the riser pipes every floor or so to keep water from going down again? (would a failure is one or more of these valves tend to cause a deep rumbling at times transmitted through the concrete?) Also this building had its 8-10 inch "filler" galvanized pipes submerged in the roof tank water that were severely rusted away after only 5 years (knife edge thin) - is this normal or defective pipes? (these pipes are at the top of the tank pointed vertically down and were extended into the water most of the time). Should they have been shorter to begin with or was water level too high or defective pipes? The managers whom I don't trust at all, just chopped about 30 inches of the ends and fitted pvc pipe as the solution, but I am worried about the rest of entire building and its riser pipes... never saw such rusting away in just 4-5 years. They chopped off similar ends in the fire sprinkler tanks etc that also rusted away. I also notice that there is no sacrificial anode installed in these tanks. why not?  (in the west there is a zinc rod in hot water tanks) Is this a violation of Thai construction code? I fear this whole building's pipes are being eaten away. Also in the roof tanks (which ran dry twice) How does the water level controller work? (it does not seem to be a float type mechanism (one sees in a toilet), but rather there is a vertical 2-3 inch pvc pipe with some vertical slots cut into it. Also shouldn't there be an alarm that goes off in the tech office when the water level drops below a certain point? All they said was that a relay had failed (seems like a single point of failure) - we can't have this tank that serves 1600 units run dry with no warning... Also is it standard to have 5 small meters/lines coming into a large building? seems pretty half ass. If anyone has some details and/or diagram showing from the street supply line to a pump, riser system to roof tank and controllers etc for how it is done in BKK I would appreciate it. I also could use some explanation on the high riser sewer tank system too... it seems they have multiple tanks (why) and some high pressure equipment running (why) and in general why even have a holding tank at all? as it is connected to the sewer system. Do high rises in the USA - West have holding tanks? Again thanks in advance for the answers.

[MRToMRT]

4 hours ago, lowp said:

huge tank on the roof and then there is a rotation of user-side pumps with a pressurized cylinder/bladder to even out the flow between pump spin ups.

In a high rise it usually gravity fed from the roof tank and then at each floor theres a PRV (pressure reduction valve) installed as there can be a very high delivery pressure due to head meters.