Water tank cooler

I live in Brazil. We are facing the opposite of the problem people have in USA: it is too damm hot. We have two huge water tanks in the top of the house. The roof is isolated, and the house is made with bricks. Most of the time we rely on the solar heater to get hot water. We also have a boiler. The thing is… It is so hot that the 9000 litres of water that we have stored upstairs get also hot.
Is there anything such as a water cooler instead of a boiler? Is there an easy way to cool our water tanks? I thought of buying ice, but I dont want to go 4 flights of stairs up carrying ice.

You can’t be the only person with this problem, I’m sure there’s companies out there that install coolers just for this.
It really shouldn’t be difficult, it’s no different then a refrigerator, except you’d have the evaporators in the tank (and possibly submerged). The question is, how much are you willing to spend on this? In USD, I’d guess a system like this, for a residential installation would run you about a grand, plus $10-$50 a month during the summer, plus a few hundred each time it breaks down if you can’t fix it yourself.

You might even be able to cobble it together yourself if you found a store getting rid of a old reach-in cooler. You’d just have to be careful not to break of the copper lines.
I’d probably also do what I could to bleach it, there’s like to be mold on the coils.

You could also try to set up a pot in pot cooling system. That is, create another tank around your water tank, open at the top. Insulate around the entire thing and fill the space between with wet sand. As the water between the two tanks evaporates it’ll draw heat from the water. When the sand is dry, rewet it so the cycle can start over.
Is it dry in Brazil? It’s not going to work if it’s humid out, the dryer it is the faster the water will evaporate and the cooler the inner pot will get.

Is there anything you can do to better insulate the water, and especially to shield them from the Sun’s heat? A second light-colored roof would help. Also good would be easily removable insulation, so you could take it off overnight for it to cool, then replace it during the day.

Are the tanks open to the air? If so, evaporation will tend to cool the water, if the loss of water is acceptable. That would also help cool it.

Any chance of running pipe between the tank and the house pipes into the ground? Then the ground would help cool the water as it flows into the house. That’s going to cost money, though.

A few other thoughts, if you’re willing to buy ice, just keep the ice in the house, and cool the water as you drink it. Or, just get a pitcher and keep water in your fridge (or on your counter). At least you can have a day or twos worth of water that’s at room temperature instead of outside temperature.

I think I had a similar problem in a very hot country; the ‘cold’ water was so hot it burned. I turned off the water heater and, as it was in the building, the water cooled and stayed cool.

For a few months the ‘hot’ and ‘cold’ taps swapped places. I drank bottled water.

The water is not for drinking - although water here in Brazil is most of the times safe to drink, it tastes weird because of some chemicals they put into it.
I really can’t make the water go all the way down to the ground. The house is quite tall.
The cold and hot water run on separate pipes - the cold water never touched the boiler.
And… it can get pretty humid here in Brazil.
I will check if I still have insulation foam. Might help if I cover the water tanks with it? They are quite huge (could probably fit 6 people sitting inside of it confortably).

What do you do with it? How does it get filled? How often does it get filled?
What’s the ambient (outside) temperature during the day/night? Is the sun on the tank?

Just to clarify:

The water tanks for my apartment block were also on the roof, and the ‘cold’ water got really hot. I turned off the water heater (which was in the bathroom) and the water in there cooled (quite considerably as the apartment had good a/c). The water heater then held enough cold water to use for washing, showering etc and I used the water from the roof as the ‘hot’ water.

We use those tanks because sometimes we dont get enough water. Water comes from the water company, is stored on a tank downstairs and pumped to the big tanks upatairs. It can also be sent to the pool.

The tanks are on the cellar, on the top of the house, therefore they are exposed for a long time. Temperatues can reach 35° c during the day and 30° on the worst nights. Thank god for air conditioning.

We use those tanks because sometimes we dont get enough water. Water comes from the water company, is stored on a tank downstairs and pumped to the big tanks upatairs. It can also be sent to the pool.

The tanks are on the cellar, on the top of the house, therefore they are exposed for a long time. Temperatues can reach 35° c during the day and 30° on the worst nights. Thank god for air conditioning.

A cheaper, (and, of course, possibly less effective), method than a couple of those mentioned, above, would be to wrap the tank in burlap and set a sprinkler to occasionally wet it down. Turning a fan on the burlap would also help. High humidity will interfere with such a plan, but it would still provide some benefit at a reasonably low cost.

If the tank was built with a double wall insulation, such efforts are probably doomed, however.

However, as also noted, if the tank is on the exposed roof, placing a smaller roof or sun shade over the tank to keep it out of the sun would be a good start. The small roof should be set far enough above the tank to avoid trapping hot air under it. Painting the “sun” side of that roof a light color would further increase its effectiveness.

Found a solution. We have a backup system that can pump water from the swimming pool (that is quite large) to the tanks upstairs. We used that twice in 10 years. The swimming pool’s water is quite colder than the water on the tanks. There is another problem - the water runs through pipes on the walls, and they get pretty warm in the sun.