Google's Liquid Cooling

I see frequent mentions of AI wasting water. Is this one such setup, perhaps with the CDU using the facility's water supply for evaporative cooling?

The CDU is inside the datacenter and strictly liquid to liquid exchange. It transfers heat from the rack block's coolant to the facility coolant. The facility then provides outdoor heat exchange for the facility coolant, which is sometimes accomplished using open-loop evaporative cooling (spraying down the cooling towers). All datacenters have some form of facility cooling, whether there's a CDU and local water cooling or not, so it's not particularly relevant.

The whole AI-water conversation is sort of tiring, since water just moves to more or less efficient parts or locations in the water cycle - I think a "total runtime energy consumption" metric would be much more useful if it were possible to accurately price in water-related externalities (ie - is a massive amount of energy spent moving water because a datacenter evaporates it? or is it no big deal?). And the whole thing really just shows how inefficient and inaccurately priced the market for water is, especially in the US where water rights, price, and the actual utility of water in a given location are often shockingly uncorrelated.

I have encountered a lot of references to AI using water, but with scant details. Is it using water in the same way a car uses a road? The road remains largely unchanged?

The implication is clear that it is a waste, but I feel like if they had the data so support that, it wouldn't be left for the reader to infer.

I can see two models where you could say water is consumed. Either talking about drinkable water rendered undrinkable, or turning water into something else where it is not practically recaptured. Tuning it into steam, sequestering it in some sludge etc.

Are these things happening? If it is happening, is it bad? Why?

I'd love to see answers on this, because I have seen the figures used like a kudgel without specifying what the numbers actually refer to. It's frustrating as hell.

AWS had a similar article a couple months ago:

https://www.aboutamazon.com/news/aws/aws-liquid-cooling-data...

In either case I cannot find out how they dump the heat from the output water before recycling it. That's a problem I find far more interesting.

I looked very hard but I don't see a way to subscribe to your newsletter?

> there is a massive influence operation that seeks to destroy knowledge, science, and technology in the United States

Agreed. Started with big tobacco by discrediting the connection to lung cancer, playbook copied by many and weaponized by Russia.

> There is no subjective measure by which the water used by AI is even slightly concerning.

Does not follow from your first point. The water has to be sourced from somewhere, and debates over water rights are as old as civilization. For one recent example, see i.e. https://www.texaspolicy.com/legewaterrights/

You are probably correct that the AI does not damage the water, but unless there are guarantees that the water is rapidly returned "undamaged" to the source, there are many reasons to be concerned about who is sourcing water from where.

The water is "used" in the sense that it evaporates. At a global average rate of 1 liter per kilowatt-hour of energy, Google claims.

Slightly old but interesting https://blog.equinix.com/blog/2024/09/19/how-data-centers-us...

This article will help you. https://www.construction-physics.com/p/how-does-the-us-use-w...

> ...actual water consumed by data centers is around 66 million gallons per day. By 2028, that’s estimated to rise by two to four times. This is a large amount of water when compared to the amount of water homes use, but it's not particularly large when compared to other large-scale industrial uses. 66 million gallons per day is about 6% of the water used by US golf courses, and it's about 3% of the water used to grow cotton in 2023.

> I have encountered a lot of references to AI using water, but with scant details.

Here you go: https://en.m.wikipedia.org/wiki/Cooling_tower

Data centers use evaporative cooling towers which evaporate water to reject heat to the atmosphere.

Even without AI the whole water conservation topic is kinda silly.

The margin at which it makes sense to save water varies wildly by location, but the cultural dominance of the western USA infiltrates everything.

Here in Zürich, my office briefly installed water saving taps. This is a city of less than half a million where the government maintains 1,200 fountains that spew drinkable water 24/7. But someone at the California HQ said saving water is important and someone at the Swiss subsidiary said yes sir we'll look into it right away sir.

Does this evaporated water stay in the loop and condense out later? Is an extra liter on the front end needed in the line until the first liter falls out of the back end?

What does that mean for environmental impact? Hydroelectric power uses water in the sense that the "used" water is at a lower altitude. What happens once that is done, is what matters.

Depending on what global average means, it seems like that's quite a lot of cycling of evaporation unless they are releasing steam at 800C

Looking up overall water usage, the US uses 27.4Billion gallons a day residential and 18.2 Billion gallons industrial. It surprised me that industrial was lower, but I guess the US manufactures less these days.

If the 1kwh per litre were accurate then judging by this calc https://www.google.com/search?q=(27.4billion+gallons+*365)*+... 37 857 903.3 terawatt hours

0.1% of The residential water use of the US would be enough to cool the entire Electicity output of the world (about 30,000TWh)

(of course, with these things it's easy to slip an order of magnitude(or several) so best check my numbers)

It means different things in different places, depending on where the water was sourced and the counterfactual of what would otherwise have happened to it. For example if you source surface water that evaporates, and the local rainshed feeds that watershed, then it's virtually closed-loop. If you're pumping fossil water out of an aquifer, and it rains over the ocean, then it's the opposite.

It's on the same level as people using incandescent light bulbs. Well we clear 160k Euros after taxes and have public medical care, and electricity is 10c/kWh here, so why does it matter what bulbs we use?

We live in an area surrounded by grass fed cows, so what does it matter if we throw away 3/4 of our steak?

Without regard to how plentiful resources are in our particular area, being needlessly wasteful is in bad taste more than anything. It's a lack of appreciation of the value of what we have.

For water specifically - it is generally speaking the most valuable resource available, we just don't appreciate it because we happen to have a lot of it.

Yes see: https://www.austinchronicle.com/news/2025-07-25/texas-is-sti...

While I'm not saying waste when things are plentiful in general is okay, I think water is a unique case that can be treated differently.

Comparing to energy costs isn't the same because using the energy for the incandescent bulb consumes that energy permanently. The gas/coal/fuel can't be un-burned. Although solar changes this as the marginal cost of that energy is free.

Comparing to food is similar. Once the food is wasted it is gone.

Water is typically not destroyed, it's just moved around in the water cycle. Water consumption in a region is dictated by the throughput the water cycle replenishes the reservoirs you're pulling from. "Waste" with water is highly geographic, and it's pretty reasonable to take exception to California projecting their problems to geographic regions that they aren't important.

I suppose in some desert-ish climate the extra moisture given to the air doesn't rain down nearby but moves with the wind somewhere far away where it rains. So there might be an effect of using locally precious water even if it's a closed loop on a continent level.

Ayyo chill. Don't let on that you know their plans. People aren't ready to know about the operations yet, so you'll come across as off balanced

> For water specifically - it is generally speaking the most valuable resource available, we just don't appreciate it because we happen to have a lot of it.

And for water specifically, the second order effects from "water saving" programs can be actually negative. Not enough water means that sewers don't work properly any more, leading from events of stink to helping fatbergs grow [1].

To make it worse, the "obvious" idea of scaling down sewer mains doesn't work either because the sewers are (at least in Europe) also used as storm drains, so if you'd scale down the sewers you'd get streets flooded.

[1] https://www.wiwo.de/technologie/blockierte-kanalisation-die-...

It doesn't even pass the sniff test because the "AI wasting water" argument comes from liberals based on ecological concerns, whereas the systematic attack on knowledge/science comes from conservatives who explicitly do not give a crap about ecological concerns

My understanding is that most new data centers don't use evaporation cooling these days, at least in water-sensitive areas. Hard to find solid data on this either way, though.

Of course, if you're using dry cooling, it uses more electricity, so hopefully you're using solar, not a source that uses evaporative cooling to produce electricity (if in a dry climate).

Anti-science sentiment isn’t exclusively a conservative thing, there are definitely anti-science liberals as well.

It still takes energy, chemicals and therefore pollution to clean water once it's been turned into greywater.

In the same way that there are toads with 6 legs, but most animals with 6 legs are insects.

Also, water is not readibly fungible as it’s not generally economic to ship large distances. So either you have it, or you dont.

If you do have it, often you have more than you can store or use effectively (the rest just runs off).

If you have a lot of water, then going to a bunch of effort saving it is indeed silly.

If you don’t have a lot of water, then it is indeed essential.

Sun is continuously running a very nice distillation cycle the size of the world that makes fairly clean water just fall out of the sky. It's only a question of where does it fall, and how much. If you want it even cleaner, wait a couple centuries for it to filter down underground, and get it from there - besides maybe a bit high mineral contents, that can easily be removed, it's essentially free, clean water. The only question is how much it's replenished in the area you're taking it from.

There's plenty of areas where there's more rainfall, than there is outflow/evaporation, with water continuously replenishing deep groundwater. "Saving water" in such areas is of little concern besides the basic, economic one of well maintenance - each one can only pull so much, and more usage means more wells, and more upkeep.

It's nothing like either of those things because both of those things have harms to other people and those harms scale linearly with the amount of consumption. Wasting steak isn't problematic because you run out of cows it's problematic because of the climate impact of raising them.

Saying that saving water is "about respect" or something is idiotic. Saving water is about ensuring there's enough water to go around. This is something you need to do in places where water is scarce and not where it isn't. And if you waste time and energy on saving water you are ultimately making the world poorer.

Obviously I'm simplifying things by talking in absolutes here, but what I said above about "the margin at which it makes sense" gets at the truth of the matter. Installing water-saving taps in Zürich is almost certainly a net harm to the environment.

This is one of those cases where we fly by and don't think much about it because we live in a plentiful environment. The more detailed we get, the more we realize that everything has a cost, and wasting water is not free as in beer. Have we also considered the disposal costs of wastewater?

I used to live in a place where water was infinite. Fast forward 20 years, now it's not anymore, the fish bearing watersheds ultimately bear the price, but everyone is still unmetered and there isn't low flow anything. If you piss away precious resources for no good reason and claim it's not wasteful, shame on you.

Yes, I have considered the disposal costs of wastewater! Yes, I still think importing hundreds of stainless steel widgets from China and then having a plumber spend who knows how many hours installing them is almost certainly a net negative. If you piss away precious resources doing that then shame on you.