# Why can't data centers recycle their water? **URL:** \ **Category:** Factual Questions\ **Created:** [June 8, 2026, 3:20pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751 "2026-06-08T15:20:57Z")\ **Posts on this page:** 20\ **Page:** 7
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [June 11, 2026, 9:03pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/121 "2026-06-11T21:03:04Z")
To make that work you need to build your datacenter immediately adjacent to dense housing. We don’t do that in the USA. Zoning & all that. ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [June 11, 2026, 9:04pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/122 "2026-06-11T21:04:45Z")
It also sounds like more of a northern thing. Water in many parts of the US is already too warm out of the tap in the summer Not all that energy efficient, either ---
**Author:** ![CaveMike](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cavemike/32/16379_2.png) [@CaveMike](https://boards.straightdope.com/u/CaveMike)\ **Post date:** [June 11, 2026, 9:09pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/123 "2026-06-11T21:09:52Z")
Cycling data center heated water back into the municipal system doesn’t help. It would still have to go through the water treatment process which would incur additional per gallon costs without value (the water is already clean). Not to mention that water treatment plants, like data centers, create significant low-temperature waste heat themselves. An alternative version of this is to require data centers to have their own retention system (like @Nightaudit 's suggestion that nuclear plants do), but that comes at additional cost as @engineer_comp_geek pointed out. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [June 11, 2026, 9:15pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/124 "2026-06-11T21:15:32Z")
Use black or grey water in the datacenter’s external cooling loop. IOW, don’t plumb them into the drinking water. Plumb them into the sanitary sewers. With appropriate screens to keep the chunky stuff out and flowing downstream. Whatever water doesn’t evaporate on the first pass through the datacenter cooling towers heads downstream to the existing sewage treatment facility. Paging @robby for a reading on my mostly silly proposal. ---
**Author:** ![TroutMan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troutman/32/6721_2.png) [@TroutMan](https://boards.straightdope.com/u/TroutMan)\ **Post date:** [June 11, 2026, 9:21pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/125 "2026-06-11T21:21:33Z")
> [@TheInkDon](#): > > No, I think what they’re saying is, don’t evaporative cool the water at all: use it, then pump the warmed water back into the municipal water system it came from. I think you’re also missing how much more water you’d need to get the same cooling effect as evaporation. If your water is coming in at 60F and you return it at 90F, it’s going to take around 35 times as much water if my calcs are correct. That mid-size data center using 100,000 gallons per day now needs 3.5 million gallons/day. If anything, this is probably optimistic for any data centers in the South, or elsewhere in summer. You probably can’t get away with much over 90F outgoing, but incoming water might be more like 70 or 80F. > [@LSLGuy](#): > > IOW, don’t plumb them into the drinking water. Plumb them into the sanitary sewers. You’re going to pump raw sewage onto evaporative towers? Screens or not, that’s not going to work well for a myriad reasons. ---
**Author:** ![CaveMike](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cavemike/32/16379_2.png) [@CaveMike](https://boards.straightdope.com/u/CaveMike)\ **Post date:** [June 11, 2026, 9:41pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/126 "2026-06-11T21:41:18Z")
> [@LSLGuy](#): > > IOW, don’t plumb them into the drinking water. Plumb them into the sanitary sewers. That was the proposal as I understood it. It has to go through the water treatment system – it can’t just be dumped into the clean water source. But this puts an additional load on the water treatment facility to treat already clean water (and all that entails). Another option is dump it into the storm sewer system (or directly into nearby water), but this is textbook thermal pollution. This assumes the waste water drains into the same reservoir that it was drawn from. This is guaranteed in Chicagoland where many suburbs draw water from Lake Michigan. Getting rid of heated water is going to be expensive with any method. I think the only cost-effective method is to find a use for the heat that offsets the add cost – like district heating, greenhouses, etc. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 11, 2026, 9:42pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/127 "2026-06-11T21:42:50Z")
> [@TheInkDon](#): > > I like that idea. Warmer water to houses means less electricity or gas to heat it, and a lot of the water use in a home is hot water. Warmer water wouldn’t hurt toilet flushing, car washing, grass/bush watering, etc. Even the chilled water and ice from your refrigerator’s door dispenser would still work, the fridge would just have to cool the water a bit more. What would be more efficient would be to have two different water inputs into the house, one (cool) for general use, and the other (hot) feeding directly into the water heater (which now wouldn’t have to work as hard). Of course, this would add complexity. The other complicating factor is that a lot of folks think that AI is in a bubble right now. When the bubble bursts, we’ll still use data centers, but probably not as many. But, how many, and which ones? It doesn’t make sense to build infrastructure dependent on the existence of the datacenter, if you don’t know how long the datacenter will last. ---
**Author:** ![CaveMike](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cavemike/32/16379_2.png) [@CaveMike](https://boards.straightdope.com/u/CaveMike)\ **Post date:** [June 11, 2026, 9:47pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/128 "2026-06-11T21:47:47Z")
> [@Chronos](#): > > What would be more efficient would be to have two different water inputs into the house, one (cool) for general use, and the other (hot) feeding directly into the water heater (which now wouldn’t have to work as hard). Of course, this would add complexity. I think if you are going to run a second pipe, then you just do district heating where it acts as a heat pipe for the cold water. This eliminates the need to treat the water in the hot system. ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [June 11, 2026, 9:49pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/129 "2026-06-11T21:49:02Z")
> [@Chronos](#): > > It doesn’t make sense to build infrastructure dependent on the existence of the datacenter, if you don’t know how long the datacenter will last. Yeah, lots of “how to make this work” discussion but there’s less engagement on “should we do it at all” ---
**Author:** ![echoreply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/echoreply/32/3641_2.png) [@echoreply](https://boards.straightdope.com/u/echoreply)\ **Post date:** [June 11, 2026, 9:52pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/130 "2026-06-11T21:52:04Z")
> [@Chronos](#): > > It doesn’t make sense to build infrastructure dependent on the existence of the datacenter, if you don’t know how long the datacenter will last. It is very easy for the shell corp that owns it to declare bankruptcy and walk away from an unprofitable data center, hurting any external infrastructure dependent on it. I think the only reasonable choice for non-evaporative cooling is liquid to air heat pumps (aka air conditioners). Use some electricity to pull heat out of the circulating cooling liquid and dump it into the atmosphere. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [June 11, 2026, 10:12pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/131 "2026-06-11T22:12:37Z")
> [@CaveMike](#): > > > [@LSLGuy](#): > > > > IOW, don’t plumb them into the drinking water. Plumb them into the sanitary sewers. > > That was the proposal as I understood it. It has to go through the water treatment system – it can’t just be dumped into the clean water source. No, no, no. I meant _supply_ lightly filtered raw sewage to the cooling towers, then take whatever doesn’t evaporate and add it back into the sewage flowing past the center and on into the existing civic water treatment facility. So they get the same gunk they always did, just with somewhat less water mixed into the goop. I do _not_ mean put clean drinking water in, then dump the used water into the passing sewage flow for (re-)treatment at the civic plant. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 11, 2026, 10:13pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/132 "2026-06-11T22:13:21Z")
> [@LSLGuy](#): > > No, no, no. I meant _supply_ lightly filtered raw sewage to the cooling towers, then take whatever doesn’t evaporate and add it back into the sewarge flowing past into the civic water treatment facility. So they get the same gunk they always did, just with some less water mixed into the goop. That idea stinks. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [June 11, 2026, 10:13pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/133 "2026-06-11T22:13:47Z")
> [@Chronos](#): > > > [@TheInkDon](#): > > > > I like that idea. Warmer water to houses means less electricity or gas to heat it, and a lot of the water use in a home is hot water. Warmer water wouldn’t hurt toilet flushing, car washing, grass/bush watering, etc. Even the chilled water and ice from your refrigerator’s door dispenser would still work, the fridge would just have to cool the water a bit more. > > What would be more efficient would be to have two different water inputs into the house, one (cool) for general use, and the other (hot) feeding directly into the water heater (which now wouldn’t have to work as hard). Of course, this would add complexity. In some areas, there are two different water inputs; one the traditional potable water for drinking and such, while the other supply is from the water treatment plant and is for non-potable use like irrigation or clothes washing. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [June 11, 2026, 10:15pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/134 "2026-06-11T22:15:15Z")
> [@Chronos](#): > > That idea stinks. Maybe co-locate it with an intensive hog farming operation? The neighbors might prefer a data center to another half square mile of hog barns. 🤪 ---
**Author:** ![CaveMike](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cavemike/32/16379_2.png) [@CaveMike](https://boards.straightdope.com/u/CaveMike)\ **Post date:** [June 11, 2026, 10:18pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/135 "2026-06-11T22:18:40Z")
> [@LSLGuy](#): > > No, no, no. I meant _supply_ lightly filtered raw sewage to the cooling towers, then take whatever doesn’t evaporate and add it back into the sewarge flowing past into the civic water treatment facility. Sorry, my mistake! It’s an interesting idea. ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [June 11, 2026, 10:21pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/136 "2026-06-11T22:21:34Z")
No, you were correct. Even “lightly filtered” raw sewage is still gross. ---
**Author:** ![CaveMike](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cavemike/32/16379_2.png) [@CaveMike](https://boards.straightdope.com/u/CaveMike)\ **Post date:** [June 11, 2026, 10:34pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/137 "2026-06-11T22:34:50Z")
> [@LSLGuy](#): > > I meant _supply_ lightly filtered raw sewage to the cooling towers I guess this is indeed done in certain places, especially water-stressed regions. It makes sense. Rather than treat the water all the way to drinking safety standards, tap off at an earlier stage and feed to large users. The water can be clean, but not drinkable. Here’s a link with a few examples: > **[Industrial & Commercial Reuse | WateReuse Association](https://watereuse.org/educate/types-of-reuse/industrial-reuse/)** > > Industrial & Commercial Reuse The Business Case for Industrial Reuse Industrial facilities adopt water reuse for a variety of business reasons: Water Security As persistent drought, increasing demand, and other pressures strain local freshwater... ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [June 12, 2026, 1:00pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/138 "2026-06-12T13:00:26Z")
> [@TheInkDon](#): > > You’d have to figure out upstream/downstream, etc, but assuming downstream users use more water than the data center needs, then the warm water would have a place to go…Of course, there’d be energy usage pumping the water back in against 50-100 psi. > [@CaveMike](#): > > It would still have to go through the water treatment process which would incur additional per gallon costs without value (the water is already clean). No, you’d just have a heat exchanger on the water main like I said in post #73. To reiterate, the municipal water wouldn’t mix with any of the data center water, they just pass by each other and transfer their heat via metal plates, tubes within a tube, or tubes within a tank, etc. No pumping required, no additional treatment/filtration, just a passive “thing” that doesn’t even require electricity except for some temperature probes and perhaps some valves. You’d still need to locate near a municipal pumping station, water tower, or large water main to get enough flow, and it would cause other problems, but I already mentioned those. ---
**Author:** ![CaveMike](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cavemike/32/16379_2.png) [@CaveMike](https://boards.straightdope.com/u/CaveMike)\ **Post date:** [June 12, 2026, 1:04pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/139 "2026-06-12T13:04:28Z")
> [@jjakucyk](#): > > No, you’d just have a heat exchanger on the water main like I said in post #73. Sorry, I misread (or misunderstood) your post the first time through. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [June 12, 2026, 1:49pm UTC](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751/140 "2026-06-12T13:49:08Z")
> [@CaveMike](#): > > Sorry, I misread (or misunderstood) your post the first time through. You can be forgiven, considering alternative proposals, like @LSLGuy ‘s plan to evaporate raw sewage [Previous page](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751.md?page=6) [Next page](https://boards.straightdope.com/t/why-cant-data-centers-recycle-their-water/1030751.md?page=8)