Water Towers.


Do they really store drinking water? Are they used to store water for fighting fires? It seems impractical to store basically a drum of water hundreds of feet in the air.

In: Engineering

The point is that if you lose power to the town they can still supply water via gravity. No need for pumps

They arent for either really. They’re used to help pressurize the water system. Pumps fill them up with water, they’re elevated, and that means if some section of the pipes loses a lot of water it drains down from the water towers and overall pressure is maintained.

>Do they really store drinking water?


>Are they used to store water for fighting fires?

Also yup since hydrants are connected to the drinking water supply. It’s easier to have one pipe system for everything.

The reason for the towers is easy. Water flows out of them naturally. If your town has a water tower and the power goes out, your water will still be there (and as just discussed, the **fire department’s** water will still be there).

The towers are also good because they smooth out water demand. Most water usage happens at two times: in the morning as people shower and get ready for work, and in the evening when more cooking and hygiene happens. To put some numbers on it, let’s say a town has a peak use of 60,000 gallons per hour at peak usage and uses 240,000 gallons per day. Using a water tower, the town can use a smaller, cheaper pump that runs continuously to fill the tower during off-hours and the tower drains during peak hours when the pump can’t keep up.

They store drinking water while also providing pressure to push water out of faucets with force. That’s the reason they’re up in the air like that.

It stores water for any purpose, and it’s tall because that’s an easy way to maintain pressure without running the pumps continuously. The demand for water isn’t constant, and electricity prices aren’t constant. You want to pump water into the tower when electricity prices are low, 3AM for example, and then you can use it when demand exceeds your pumping capacity, or energy prices are high.

Basically it works like a hydraulic system. The pressure exerted on the water by gravity helps to pump out the water from your tap by giving it pressure.

In flat areas like the American Midwest, they are used to pressure water for faucets and such. The reason you only see them in flatter areas is because in more hilly areas you can just use a reservoir in the hills

[Hear you go.](https://www.youtube.com/watch?v=yZwfcMSDBHs)

tl;dw: Basically, they maintain pressurization regardless of the demand on the system. If there’s a sudden spike in demand, it can take several minutes for pumps to come online so water towers make up the difference. Also, if there’s a drop in demand, the water produced by the now surplus pumping pushes the water back into the water towers.

It handles the surges in demand, so that pumps only need to be sized for average demand instead of peak demand.

yes, drinking water, the municipal water that everyone uses. Not sure if that includes the firefighting lines, though I suspect it does. The height is necessary to keep pressure. The height and the huge size make it work perfectly and completely passively – it maintains pressure even as it’s drained (height), and the shear size means it levels out the load on the water system.


They’re fine for small towns/areas. There aren’t a lot of fires there anyway, and firefighters in those areas are volunteers and barely even do anything to put the fire out, so I don’t think running out from trying to stop a fire is an issue. Though if it does run out, so what? It’s just a small town, and the water will be refilled by the next day

Just in case you’re curious 2.307 ft = 1 psi. So 23 ft is 10 psi. Generally the bottom of the bowl is 100’ up, and the top is 140’ So 45-60 PSI depending on how full it is. If you put a pressure gauge in your house, you would see it rise and fall diurnally.

Fire protection is huge for homeowners insurance rates, which in turn affects housing prices.

And, like others have said, you can treat the water in batches, and still maintain a constant pressure.

20 PSI is the magic number. Under 20 and a boil order is issued.

Most water is treated well water. The simplest is simply chlorinated. These days, it’s usually just sodium hypochlorite (bleach). Next is fluoridated if there isn’t enough naturally (hydroflurocylic acid). Next would be filters, kinda like the water softener in your house but as big as your house. It gets backwashed just like yours. (As a side note, deep wells can contain radium and barium which get concentrated in the backwash, and in the last 10 years people have started dealing with that)

Last but not least is surface water treatment, which is a whole different animal.

Some places use low pressure reverse osmosis (LPRO). Here’s a disturbing fact: let’s say your legal limit for barium is 2 mg/L. If your well has 3, then they’ll run half of it through the RO and blend it with the other half, so now it’s down to 1.5, which is within the limit.

I worked for a municipal engineering design firm for many years, then jumped ship 7 years ago to work directly for a municipality.

What else do you want to know?

The purpose isnt necessarily to store water, but to pressurise it.

Water flows downhill. This means that is you have a reservoir of water up on a hill feeding houses down in the valley below, gravity will cause the water to flow from the reservoir to the houses, and have enough pressure at the end to flow out of of taps.

This is a problem if you live somewhere very flat – if your water supply is at the same level as your end user, there is now no drop in height to create that flow, and we need to do it artificially.

You could just attach a pump to your water supply to push the water through and pressurise it, but water use isn’t predictable – you would need a way to have a big pump running when lots of people need water, but somehow also turn it right down when only a few people are running taps. At the moment we just don’t have a way to adequately detect and pressurise a system quick enough for this to work.

The answer is the water tower. To create a nice consistent pressure, we want a change in altitude between the supply and end user, so we can just make that ourselves by lifting the water supply up into the air. The water is up high, and as it flows down the pipework to the houses below it creates a suitable head of pressure.
Because it is a big tank up in the air we do need to pump water up there to fill it, but rather than needing to do this continually and vary the pump to match the demand, we can just pump up water when the tank gets below a certain level, turn it off when the tank is full, and then let the tank empty as it is used – turning the pump back on when the level drops again. This is a much simpler system as we just need to turn the pump on/off to fill a tank, rather than trying to vary it to match demand.

Rule 7 requires that you search the sub before posting.

**Please read this entire message**

Your submission has been removed for the following reason(s):

* ELI5 requires that you *search the ELI5 subreddit for your topic before posting*.
Users will often either find a thread that meets their needs or find that their question might qualify for an exception to rule 7.
Please see this [wiki entry](http://www.reddit.com/r/explainlikeimfive/wiki/how_to_search) for more details (Rule 7).

If you would like this removal reviewed, please read the [detailed rules](https://www.reddit.com/r/explainlikeimfive/wiki/detailed_rules) first. **If you believe this submission was removed erroneously**, please [use this form](https://old.reddit.com/message/compose?to=%2Fr%2Fexplainlikeimfive&subject=Please%20review%20my%20thread?&message=Link:%20https://www.reddit.com/r/explainlikeimfive/comments/p4kvsl/eli5_water_towers/Please%20answer%20the%20following%203%20questions:1.%20The%20concept%20I%20want%20explained:2.%20Link%20to%20the%20search%20you%20did%20to%20look%20for%20past%20posts%20on%20the%20ELI5%20subreddit:3.%20How%20is%20this%20post%20unique🙂 and we will review your submission.