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JohnnyJordaan t1_jdsi8n1 wrote

They are local pumps in various part of the system to ensure the local pressure is high enough to reach around 6 stories high while then still having enough pressure coming out the tap on the top floor. Buildings that are larger than that needs to use their own pump to pressurise it further to reach the higher floors. They often combine it with a water storage tank on the roof, to not require huge pumps to meet demand when everyone is taking a shower at the same time.


Imhumanator t1_jduastc wrote

Would this mean lower floors could potentially have higher pressure I’m the < 6 story scenario?


JohnnyJordaan t1_jdulje6 wrote

In a large building the pressure would generally be higher in the lower floors as there’s more water ‘leaning’ on it from all the floors above it. However as there are safety regulations for the maximum pressure at any point in the system, they often use pressure valves to make sure it will not rise above a certain pressure (eg 75 psi). So that way you generally won’t notice a difference between the floors in a building. In a small building without pressure valves it’s true that the lower floors will have the highest pressure.


fiendishrabbit t1_jdunnkg wrote

The potential is there, but there are water pressure regulators installed that lowers the pressure in the tap to where it's supposed to be.


fiendishrabbit t1_jdunefw wrote

There are a lot better reasons for a water storage tank on the roof than "to not require huge pumps to meet demand when everyone is taking a shower at the same time".

Pumping into a tank means that the pump does not experience any water hammer effects (which can ruin the pump) and it means that water pressure from the tap is even (since the pressure is determined by the height difference between the water surface and the tap) rather than fluctuating as it would if it was actively pressurized by a pump.


JohnnyJordaan t1_jdupfmm wrote

Those are indeed important advantages but not strict requirements for the system to function, I meant it in that regard.