[dhampi]

Presumably a lot less expensive than pumped hydro to build.

[thereisnospork]

Pretty much zero chance of that. The complexity (moving parts, machined parts, number of generators, number of electrical interconnects (etc.) is so much higher per kilogram basis compared to pumped hydro. Much of the country does half of pumped hydro (storing potential energy in water towers) and delivers it to your door for fractions of a penny per kg, a price that includes a complete distribution network and sourcing/purification of the water.

[nerdsniper]

My understanding is that water towers mostly exist as something to “pump against”, rather than being a vessel that gets filled and emptied repeatedly like a battery would. It does vary in level a bit, often with a circadian rhythm (but also randomly pulsatile). I just don’t think it’s a significant portion of the total water flow that its pressure supports.

[napkinartist]

You have to dredge pumped hydro though. Silt accumulation is a challenging engineering problem and erases capacity over time.