Compass investigation: Cayman’s water – Where it comes from, where it goes …

Cayman’s most precious resource comes from 150 feet below ground and snakes through a modern array of devices to arrive at your home at the flip of a faucet handle. Fresh water, so crucial and so scarce in nature, has always been the lifeblood of a prospering community, and advances in desalination technology have been the hidden engine fueling Cayman’s growth over the last few decades.

The local population has tripled since the advent of the Water Authority in 1983, and the demand for fresh water has increased exponentially as more people have come to call Cayman home.

The water you drink, the water you bathe in, and the water you use to irrigate your lawn all come from the same place: Extraction wells that use the ground as a natural filter. Modern ingenuity has allowed companies to pull fresh water out of seawater and to pipe it tens of miles away from the source.

RELATED STORY: Dealing with wastewater 

The water business, unlike others in a capitalist society, benefits from being a utility. Manuel Thomaz, the general manager for Cayman Water, likens the water grid to a “legal and natural monopoly,” and he said that competition between rival water companies could have drastic repercussions for society.

“You just have one pipe going into your house,” said Mr. Thomaz, explaining what he means by natural monopoly. “It would be very expensive to have two or three pipes coming in to the same homes for different operators.… It’s really a very serious business. Everybody needs water. You cannot live without water. And when water is not [of] the proper quality, you’ll have public health issues in the region.”

The water that comes out of Cayman’s taps is tested at 25 different sample points by the Water Authority to ensure that it is clean and that there are no problems in the distribution network.

Cayman’s water supply ranks as one of the most efficient in the region in terms of water loss, but interestingly, the public does not seem to know it. According to the 2010 census, 88 percent of Cayman households have potable water available through their water mains, but 79 percent of households consume bottled water.

Frank Armas, plant manager for Cayman Water, stands in front of the trains of semi-permeable membranes that serve to separate the fresh water from the salt water. – Photos: Taneos ramsay

Seven percent of Cayman residents receive their water through cisterns, and another five percent use wells. Those numbers skew higher if you are in East End, North Side or the Sister Islands, but for the most part, Cayman households have far better access to fresh water than they did two generations ago.

“We need to really explain to everybody what it takes to get 100 percent quality water, 24 hours a day, in their taps,” said Mr. Thomaz. “Consumers don’t imagine how much effort that takes. You just give value to the water service when you don’t have it in your tap. Then you think, ‘Oh god, what am I going to do now?’ But in developed countries, it’s normal to just turn the tap and the water is there.”

The history of Cayman’s water supply

Historically, the people of the Cayman Islands relied on cisterns to collect and store rainwater, and Grand Cayman’s natural topography contains three significant freshwater lenses. A lens is defined in hydrology as a layer of fresh groundwater that floats on top of a dense layer of seawater.

Those oases – located in Lower Valley, East End and North Side – were enough to sustain a very small population, but as Cayman began to grow, there was a fear that the natural resource would be exhausted.

Cayman Water, a private sector company that is a fully owned subsidiary of Consolidated Water Co., was the first party to provide fresh water to residents of Grand Cayman. Cayman Water was developed in 1973 for the purpose of providing water and wastewater services to Governors Harbour, and after two years, it was capable of producing 20,000 gallons of fresh water per day.

Back then, the only method for converting saltwater to fresh water was distillation. The seawater would be boiled, and the resulting vapor would be collected and cooled. As the resulting product condensed, it would produce both pure water and a waste product that mostly consisted of brine.

The latest energy recovery devices are an improvement on the DWEER concept first adapted by William T. Andrews of Consolidated Water.

That process was less than ideal for a number of reasons. For one, it would take a significant amount of heat – created by diesel-fueled impellers – to boil the water and rid it of its impurities. Second, the seawater, steam and hot brine created an extraordinarily corrosive environment for the machinery.

Distillation was not necessarily economically efficient, but it was the best process available at the time. Cayman Water was slowly able to ramp up its production and storage capacities over the next few years, and in 1979 it was granted an exclusive 20-year license to process and supply water.

But as that private sector company began to thrive, the government also saw a need to become involved with the water infrastructure. The Water Authority came into existence in 1983 and began safeguarding the island’s natural groundwater resources and plotting out the future of development in Cayman.

“The geology of the Cayman Islands is unique. It’s a very porous geology that we have here,” said Hannah Reid, corporate communications officer for the Water Authority. “Our limited fresh water lenses ‘float’ on the saline groundwater and are recharged by rain. The saline groundwater is directly connected to the sea.

“When we abstract groundwater for our [reverse osmosis] plants, we’re not tapping into a freshwater lens. We’re actually pumping from the saline groundwater, which is basically seawater in terms of its composition.”

Cayman Water kept the responsibility of providing water to the residents of Seven Mile Beach and West Bay, and the Water Authority began distributing water to George Town and beyond. The Water Authority also took on the task of providing sewer services to Cayman’s growing population.

The lay of Cayman’s water table changed for good when the first reverse osmosis plant was built in 1989, and now, decades later, the two companies have maintained and deepened their partnership.

Today, there is one reverse osmosis plant in Cayman Brac, and there is also a containerized plant that may ultimately be transferred to Little Cayman. Little Cayman does not have any significant freshwater resources, and only 14 percent of households in the Sister Islands are connected to the water grid.

Manuel Thomaz, general manager of Cayman Water, explains how some of the plant’s automated features work.

The Water Authority owns four reverse osmosis plants in Grand Cayman, but it allows Cayman Water to manage the daily operations at the facilities in Red Gate, North Side and North Sound.

Cayman Water pulls the salt out of the water at those plants and sells it to the Water Authority, and the Water Authority in turn sells it to nearby customers. That operating agreement is set to elapse soon, but Cayman Water’s Mr. Thomaz said it has been good for both parties and he hopes it continues into the future.

“It’s good for us because it’s our business. It’s our life,” he said. “I think we do it in the most efficient way possible. It’s good for them because they have well operated plants and they know we know how to maintain the plants. When they get the plants back, they know they’ll be receiving them in good shape.”

Potable water

Creating potable water from saltwater, it turns out, comes down to some pretty simple science.

Drinking water comes from groundwater drawn from 150 feet beneath the surface, and it’s not drinkable in its natural form. It’s salty and filled with impurities. It is pumped to the surface and passed through filters that screen anything larger than five microns, the size of a human red blood cell.

Click to enlarge

“Pre-filtration is much easier than if we abstract water directly from the open sea,” said Mr. Thomaz. “When you get it from wells, water comes in very good shape. It’s already somewhat filtered. We get it from deep in the ground, so we don’t get stones and we don’t get algae. It’s still seawater, but it comes from the ground. If you had it coming from the open sea, more pre-treatment would be needed.”

After the water is filtered, it’s sent through a network of vessels with semi-permeable membranes designed to filter out salts. The water is sent through the membrane array at extremely high pressure, and the membranes separate the fresh water into one collection point and a brine solution to another.

For every 10 liters of water taken from an extraction well, the process yields four liters of fresh water and another six liters of brine solution. The brine solution is eventually recycled and sent to a disposal well deep underground, and the fresh water continues the journey from plant to your sink.

When the salt is being removed from the fresh water, the seawater is pushed through the pipes at a pressure rate of 800 pounds per square inch. The brine solution still maintains that force and energy when it’s separated from the potable water, and it took a local invention, the DWEER – Dual Work Energy Exchange Recovery device – to make the process of desalination more energy efficient.

The DWEER – which has since been improved upon – was invented here in Cayman by William Andrews, a former director of Consolidated Water, and it allowed the residual energy from the separation of fresh water and seawater to be reused in the process.

“When the water comes through the feed wells, you have to get up to 700 or 800 PSI,” said Karlene Singh, a project engineer who works in business development for Cayman Water. “When you literally push the pure water out of the membranes, what you’re left with is a concentrate at very high pressure. So instead of just disposing it straight to the disposal well and losing that pressure, this device – an energy recovery device – takes that brine and uses it to pressurize the low-pressure feed water. The brine transfers its energy and becomes low pressure, and then you can just dispose of it.”

Cayman’s groundwater also contains hydrogen sulfide, which lends a funky smell and taste to the potable water. The sulfur is removed through a degassifier tower, and other essential elements – such as tiny amounts of chlorine – are added to the water before it arrives fully drinkable at your kitchen sink.

By the time the water arrives at your home, it has had 99.9 percent of the salts stripped from it, and the World Health Organization dictates that it must have less than 600 milligrams of total dissolved salts. In Cayman, it’s even cleaner, measuring less than 200 milligrams of dissolved salts per liter.

Once the salt has been removed, the potable water is ready to slide through the pipes and out to the thousands of households that get water service on Grand Cayman. Cayman Water produced 898 million gallons of potable water in 2017, and it’s currently constructing another plant to ramp up production.

Giant tanks hold millions of gallons of water at the Cayman Water plant off the Esterley Tibbetts Highway. – Photo: Taneos Ramsay

Maintaining the plants

Cayman’s reverse osmosis plants are finicky creatures with lots of moving parts, and Cayman Water has built and maintained a warehouse full of the pieces needed to keep water production rolling.

The local plants have a production capacity of 3.7 million gallons per day, and they are capable of producing water at half-capacity on generator power alone. In three years, Cayman Water plans to have a daily production capacity of 4.9 million gallons and a storage capacity of 13 million gallons.

Those capabilities have been designed with a Hurricane Ivan-level disaster in mind. Mr. Thomaz said that if a major disaster befell Cayman, the community would have enough water in storage for four days.

“I think we have a very resilient system,” he said. “Our new infrastructure is hurricane-proof. It would have to be a very strong storm to affect us. But the thing is, we are totally dependent on electricity, so we have installed generators that produce energy for part of our water production capacity.”

Cayman Water’s reverse osmosis plants have placed all their electronic and computer equipment on the second floor, far out of the reach of the devastation that could be unleashed in an islandwide storm. The actual location of the pipe systems – which were at one point identified only by employees with institutional knowledge – can now be found by GPS even in the midst of storm-related debris.

The level of automation at Cayman’s water plants might surprise some. For instance, Cayman’s plants are autonomous, and they run at full speed until the water storage tanks are full. When the tanks reach full capacity, the computers tell the pumps to stop producing and the plants turn off by themselves.

The plants can also tell when people are using water at a volume greater than normal, and they can compensate by automatically sending more water into the system.

“We have five pressure settings throughout the day,” said Mr. Thomaz. “For the day, it’s at high pressure, 60 PSI. We send the water out at 60 PSI pressure, and if by any chance that pressure gets lower, it means the network is demanding more pressure, so the pumps just pump a little bit more to keep the pressure at 60. From midnight to 5 a.m., that’s the lowest pressure setting. It’s 45 PSI, but if by any chance there’s demand, the pressure tends to go down, so pumps will spit out more to keep the pressure up. Those pumps are always up and down to keep the pressure at that level.”

Cayman Water has also conducted computer simulations to map pipelines and demands on different areas and to project the effects of tourism and population growth 10-20 years down the line.

But one of the main things working in Cayman’s favor is its relative youth. The population boom on Grand Cayman has mirrored the rapid improvement in desalination technology, and Cayman has been able to lay its water pipe network with both incremental and long-term growth in mind.

The pipes – made of PVC, which have a lifetime of 50-100 years – are so sturdily built and rigorously monitored that Cayman Water loses less than 10 percent of its water to leaks. By contrast, Jamaica has losses of nearly 71 percent of its produced water, and the World Bank estimates that 32 billion cubic meters of water is lost annually due to leakage in developing countries.

“It’s really amazing how this company can have non-revenue water below 10 percent. It’s not at all normal even in the best utilities around the world,” said Mr. Thomaz, who previously worked in Portugal’s water industry before relocating to Cayman. “Desalinated water is very expensive, so every gallon you lose is like throwing Cayman dollars out the window, and that’s why Cayman Water is so focused on controlling and reducing its non-revenue water levels even further.”

The costs of being prepared for every water-related emergency are playing out in Cape Town, a heavily populated city in South Africa that is experiencing a profound water shortage. A lengthy drought and poor foresight in the field of water desalination has led Cape Town to the verge of a total water shortage, and its residents have been forced to ration water in order to preserve the existing supply.

Cape Town is the first major city that faces a total water shortage, and the government is building water desalination plants to stave off the humanitarian crisis. Day Zero – the day when Cape Town will have no water left in its municipal supply – was believed to be imminent, but was recently pushed back to 2019.

“They don’t know what’s going to happen,” said Mr. Thomaz of Cape Town. “It’s going to be a national security issue. And the thing with South Africa is they just react to things. This was forecasted 10 years ago, that this could happen, and they didn’t do anything. Now, they face a problem and they have tenders out to do four desal plants. There’s no reason why a coastal country should be short of water, besides the money to build plants. But when you’re talking about an essential product like water, money is secondary. When you face drought and a total shortage of water, money is nothing.”

Support local journalism. Subscribe to the all-access pass for the Cayman Compass.

Sign in, or subscribe


  1. A bit long and somewhat complicated and confusing article.
    I would have started with a map of the island showing water supply source for each area and another map showing how each area disposes its dirty water.

    The way I understood, the water to George Town comes from underground, not directly from sea, as I thought, then purified.

    If seven percent receive water from cisterns and five from wells, then why these numbers are higher if you are in East End or North Side? 7&5 % where? Confusing.

    Where does water for reverse osmosis plants comes from? The one that supply Red gate and North Sound?

    I also disagree with the assumption that people don’t know the water is safe to drink. You read about it in onboard magazine. Yet, every houshold I personally know uses bottled water. At work, we drink water from large blue bottles. Something is not right here and it is not the lack of awarness. PVC pipes? People are not stupid. If water smells and tastes good they would drink it. So why people refuse to drink tap water?

    • What can I say, the article left me ( a lay person) with more questions than answers. In my opinion it is not very concise.

      And I still want to know why people don’t drink tap water. Spending so much time, efforts, money and resources to produce and advertise clean water people don’t drink?

      I would also want to know how health hazards for workers at biological waste treatment plant are mitigated. Volatile organics in wastewater may be vaporized or air-stripped during treatment. Many of the compounds are carcinogens and/or mutagens, so sewage workers may be at increased risk of cancer or adverse birth defects.

      How about rupture hazard from water storage tanks? Are they double wallled?

      I hope Part 2 of the investigation is coming to complete the picture.