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Comment by vidarh | Hacker News Reader

> It seems like we're mixing up terms here and miscommunicating. I thought we were talking about actually replacing the water here (as in, down the drain, fresh water from the tap)

We are. I changed it while you were writing.

Everything I'm seeing suggests typical loss to backwash of the filters for a short course pool is in the 5k - 10k liters of water a day range, possibly less if you invest in expensive additional filters. 5k a day is ~1.8 million liters a year.

To get below a full replacement every year for a small short-course pool, you need to lose less than 1370 liters a day, or ~1.4 m^3

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You're shifting things from normally needing to fully drain and fill the pool multiple times a year from specific contamination events to now talking about routine backwashing events, which I agree do happen as a part of normal routine maintenance (a part of the "partial drain" and "good filtering" I was talking about before).

I agree you'd probably use something like 5-10k liters of water for a backflush for filters that size, but that wouldn't normally be a daily thing. The amounts needed here would be highly variable depending on a wide range of factors.

I still stand by if you're having to actually fully drain and refill your pool multiple times a year (as in, an actual drain and fill, not slow partial replacement from weekly/every other week filter flushes) you're either very unlucky or you don't know what you're doing maintaining the pool.

This went into the weeds a little bit, but I've tried going over the figures again. I'm not sure if I'm missing something here or someone got some units wrong somewhere, but data centers seem to use far more water.

A medium size data center consumes 300k gallons of water per day [0]. That's over 400 million liters per year.

Even if we go with the highest estimate vidarh gave of 1.8 million liters per year for a full-size olympic size swimming pool, that's a tiny fraction of what a typical data center uses.

[0] https://www.eesi.org/articles/view/data-centers-and-water-co...

> A medium size data center consumes 300k gallons of water per day

Not always true. This can vary greatly based on datacenter design. A medium sized datacenter proposed near me was planned to only use 300 gallons a day for example.

Your source even points to this being highly variable, assuming you pay attention to their wording.

> Large data centers can consume up to

"Can consume", "up to". Not some hard truth that they will consume that much.

Fair point. If you divide the 163.7 billion gallons annually among the 5426 data centers, the figure does come out lower at ~30 million gallons or ~100 million liters annually. That's still far, far larger than the largest swimming pools.

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