water towers …


How do water towers work? Where does the water come from? How does it get in there? How much? WHY! What do we do with it? Why are they in such random places ???

In: Engineering

It’s easier to pump water up to a tower and then use gravity to distribute it than it is to pump water directly to where it will be used. Each household could have its own pump and bring the water up to each apartment, but by having a single system and using gravity to keep water always pressurized, things are a lot less complicated and easier to fix, not to mention cheaper.

So basically water towers are there for storage, mainly in older towns. During the busy times of the day 5-7 am and 6-9 pm, when people are showering, cooking, etc. Some cities water pumps can’t keep up with the load. Water towers were invented to help combat that. Basically during the rest of the time, they slowly get filled up, so when the time comes when there is an increase in water demand, the water will get taken out of the tower and distributed to houses. They’re built high up so that gravity can help maintain the water pressure.

Water towers are used to provide water to buildings that are higher than the water source.
When the water source is higher than the building, gravity will carry the water there. However, if the building is taller than the water source, then a pump is required to get water to all outlets in the building. Water towers are built to be higher than the surrounding buildings so pumps aren’t needed to get water from the tower to the surrounding buildings, just one large pump is needed to fill the tower itself. Many rural towns have water towers but some city buildings also have water towers set up on the roof since they are often taller than their water sources. This means that so long as there is enough water in the tower, everyone connected to it will have access to some water, even during blackouts or mains water failures.

So I’m a controls engineer, and while I’ve never designed or programmed a water system, I’ve done some deep dives into their instrumentation and control schemes and therefore have a fair understanding of how they work.

Water towers are a way to pressurize a water system without constant use of mechanical means. The water generals comes from a well or reservoir, and if the municipality has a treatment plan then what is in the tower will be treated (chlorinated or filtered, other chemicals possibly to raise pH, etc.).

Towers are filled from pumps on the ground that take the water from whatever source and fill the tower. This saves money, because the pump only has to run until the tower is full. In a large city (I have some knowledge of the water system in the las Vegas valley), they use pumps to keep the mains pressurized because there is always demand. At lower demand times, the system can use less pumps but they always need pumps. Smaller towns don’t, so a tower allows them to keep the mains pressurized without a pump running. The tower also acts as a buffer so that the pumps don’t even have to be sized to keep up with instantaneous demand, the pump can be a smaller unit that fills the tank as it gets low.

I assume placement isn’t random, but that it is the best location for proximity to the water source and elevation to allow for the pressure needed to push water where it’s needed.

It’s for storage, to buffer the plumbing system against the ebb-and-flow of a community’s daily water demands, and to help guarantee that water is delivered to its users at high pressure. The water pressure in a closed system of pipes, depends primarily on how much vertical distance there is between the user and the water level in the reservoir. If the city’s water reservoir were a big lake that’s 5 meters downhill of everyone’s house, then you could plumb everyone’s faucets up to that lake, but the water wouldn’t run when they tried to run a bath. Not unless they used a pump to push the water uphill from that lake, anyway.

But if instead the town dammed up a little lake which was 20 meters *above* them on a big hillside, then they could just run a sealed pipe system straight from that lake to their houses, and when they ran the shower, it would come out with plenty of force – no pumping needed.

Damming up a lake at the top of a hill is an expensive and sometimes risky idea, and sometimes there isn’t a hill at all. So the next best thing is to put a great big water tank at the top of a big metal tower.

Usually, the water gets up there by being pumped from some larger reservoir that’s closer to ground level. Sometimes, if the tower serves a very remote area, it might be filled by a big water-tank truck coming by periodically.

A public water supply must maintain 3 basic standards- quality, demand, and pressure. Quality is handled at the water plant, then water is pumped out to the distribution system. Water towers equalize demand and, more importantly, pressure. If your town uses 2 million gallons a day, the plant’s pumps can make a constant 1400 gallons a minute 24/7 and keep the towers full. Spikes in demand from morning and evening showers are accounted for with adequate tower volume. Pumps and chemical dispensers last longer under constant load.

Pressure, however, is primary. Water distribution lines crack, and joints fail. Adequate pressure(>35 psi) means that clean water leaks out and icky ground water doesn’t leak in. Keep in mind that water lines often go under roads, cars leak oil, ag chemicals wash off into streets, roadkill happens, etc. Gross, right? Well the height of the water column in the tower is what determines pressure in the lines. Shape and volume of a water tank don’t actually influence pressure like we imagine they might. It’s a straightforward .43 psi per foot of water height. If power goes out at the plant, the supply in the tank keeps pressure high enough to keep your water safe until we can fix it.

As for being in odd places, the towers go where a spot is available. Same reason county roads are bendy- they’re often built on parcel borders where land is cheaper and easier to get.

Think of a water tower as a rubber band between the supply and demand sides like [this](https://i2.wp.com/66.media.tumblr.com/41a34e595c5b56173c03be8486ff95be/tumblr_inline_pjj52sYjyM1qzrgfe_500.gif?resize=500%2C281&ssl=1) so there are no huge spikes/dips in what the pumps “see” in the system. There is a video on them [here](https://www.youtube.com/watch?v=yZwfcMSDBHs)

Water towers are filled with excess capacity from the local water company when the public demand is lower than average (i.e.11PM – 4AM) and they are used as a buffer to meet demand when it spikes, i.e. 6AM when lots of people are taking showers before work.

Let’s say the town uses an average of 24 million gallons per day. So the town builds a water plant that can produce enough to meet the average demand, now there is a problem that overnight you have to cycle pumps on and off because of low demand, causing extra wear and tear on the pumps. But more importantly you can’t meet the extra demand in the morning because your pumps can only move 1 million gallons/hour but demand has spiked to 2 million gallons/hour. It is not economically feasible to have double the number of pumps needed just for the morning rush and you can’t just ‘hit the gas’ on pumps to get them to work faster without sacrificing power efficiency(expensive) and equipment life(even more expensive). This also doesn’t take into account the water treatment plants needed to make the water meet health and safety standards which are huge investments in their own right.

So if you add a water tower, you can keep the pumps and treatment plants running at the ideal speed and when demand is low the towers refill, and the towers feed the system during peak demand.

Water only flows downhill.

This is a problem if you live somewhere very flat, as without a slope between the source of the water and your end user, it won’t flow from one to the other.

You can get around this by using a pump to push the water – the pump creates the pressure needed to move the water instead of the slope. The problem is that you don’t want you pump working when nobody is using any water as you will just burn it out, but if you turn it off you won’t have water available when people do need water.

One solution is a water tower. By lifting the water up high in the air, you artificially create a slope in your pipes. So your water always has enough pressure to flow along the pipes and out of the tap.

One downside is that you need to get water up into the tower in the first place, but for this use a pump is a good choice – you can turn on the pump, fill up the tank on the tower, then turn the pump off again. Let the tower empty naturally as people use the water and just turn on the pump again when the level gets low.