# Why did the Romans bother to build aquaducts? **URL:** \ **Category:** Factual Questions\ **Created:** [January 6, 2011, 1:28pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602 "2011-01-06T13:28:26Z")\ **Posts on this page:** 19\ **Page:** 2
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [January 6, 2011, 8:18pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/21 "2011-01-06T20:18:46Z")
> [@mbh](#): > > This. The law of communicating vessels is lovely in theory. Getting it to work properly in the real world is a nontrivial engineering problem. Especially with bronze-age technology. Your point is probably still valid, but the Roman empire was iron age, not bronze age. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [January 6, 2011, 9:38pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/22 "2011-01-06T21:38:05Z")
Required watching: [![](https://img.youtube.com/vi/oK0NRgbZVmA/hqdefault.jpg "History of the World Part 1 Plumbing") ](https://www.youtube.com/watch?v=oK0NRgbZVmA) ---
**Author:** ![Jake](https://avatars.discourse-cdn.com/v4/letter/j/f475e1/32.png) [@Jake](https://boards.straightdope.com/u/Jake)\ **Post date:** [January 6, 2011, 10:03pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/23 "2011-01-06T22:03:17Z")
(Aside)…How did they “Un-filter” the water when it reached its destination? Or did they just drink sandy water? ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [January 6, 2011, 10:09pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/24 "2011-01-06T22:09:47Z")
Sand settles. The water commish ensured the highest quality water went for drinking. Some aquaducts were covered almost entirely. Sand and some silt are about the easiest things to deal with. ---
**Author:** ![smiling\_bandit](https://avatars.discourse-cdn.com/v4/letter/s/e9a140/32.png) [@smiling\_bandit](https://boards.straightdope.com/u/smiling_bandit)\ **Post date:** [January 7, 2011, 12:48am UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/25 "2011-01-07T00:48:40Z")
Another reason to have high-level pipes - Once you got the water inside Rome, you had to break up the piping and redirect it. That would be a lot harder with underground pipes when you don’t have backhoes and complex printed construction plans on a hydroengineer’s PC. You’d have to figure out where the pipes go, try not to tear them up while not completely wrecking an entire street or square. That’s a bit annoying even today. ---
**Author:** ![Pantani](https://avatars.discourse-cdn.com/v4/letter/p/87869e/32.png) [@Pantani](https://boards.straightdope.com/u/Pantani)\ **Post date:** [January 7, 2011, 4:40am UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/26 "2011-01-07T04:40:55Z")
Frontinus is your goto man for Roman aquaducts. He wrote a nice little account of how he reparied and improved the aquduct system under the Emperor Nerva. I also suspect he would have been the worlds most boring person to be stuck next too at a dinner party with his lengthy list of water volumes and discriptions water quality. One of the things you need to realise is that slave labour isn’t free, indeed for specialised and skilled labour it can be very expensive. Repairs seem to have been generally done by, in Rome’s case, two work gangs. One paid for by the public purse and one by the imperial purse. Repairs would include cleaning out sand and silt and, more problematic, calcium carbonate deposits. Leaks were plugged and illegal private tapping of the supply was found and eliminated. Major works would usually be put out to contract. ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [January 7, 2011, 9:48am UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/27 "2011-01-07T09:48:16Z")
A sealed water system also has the risk of [hammers](http://en.wikipedia.org/wiki/Water_hammer) occurring, which can increase pipe pressure immensely. With lead pipes (almost certainly with a folded seam) such events would rip pipes apart. I remember an article (maybe _Scientific American_ in the 70’s) that indicated that Roman engineers understood hammers and built suitable remediation in sealed systems, but this understanding may have informed the decisions to use open aqueducts. Si ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [January 7, 2011, 10:12am UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/28 "2011-01-07T10:12:52Z")
> [@Quercus](#): > > Also pressure-tight pipes require a lot more maintenance and tend to fail catastrophically, wheras a leaking sloped aqueduct just loses some water. Leaking hardly matters – the Roman water system had no turnoffs – it ran all the time. Water not used just ran out the end, into the ground or the sea. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [January 7, 2011, 1:03pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/29 "2011-01-07T13:03:34Z")
Leaking mattered, as it affected the flow. Flow was important. By the time the water arrived, it probably mattered a lot less. I believe that when they needed to actually pipe it and pressurize it, they did when it MUST be done, such as when clearing a valley and getting the water to flow up hill. The Romans didn’t like dealing with the blowouts, etc. There are books written by the builders, by the folks left to maintain the system and there is much known on the subject. Maintenance and more maintenance, like any public utility, was key. And, lest we forget what the Romans figured out: K.I.S.S. Keep it simple, silly. We tend to believe that something ‘more advanced’ (pressurized pipe or a system that doesn’t waste much) is somehow better. What made things better for them was saving time, materials and some other things. Like so many historical projects, it’s easier to wrap one’s brain around the math, tools and engineering, but oft seems impossible to get one’s brain around the culture. That drives the final project. This lesson carries over through all times. . ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [January 7, 2011, 1:13pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/30 "2011-01-07T13:13:19Z")
Weren’t the aqueducts a tempting target for military invaders? I recall Rome was under seige a few times. Poisoning the water with dead animals would be a rather nasty strategy (much like using catapults to fling carcasses over walls). I’ve seen pictures of the remaining aqueducts and they seem to meander across the countryside. It’s looks like defending them would be very difficult. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [January 7, 2011, 1:16pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/31 "2011-01-07T13:16:10Z")
> [@](#): > > I believe that when they needed to actually pipe it and pressurize it, they did when it MUST be done, such as when clearing a valley and getting the water to flow up hill. The Romans didn’t like dealing with the blowouts, etc. Romans didn’t use pipes to clear valleys – they built aqueducts on bridges to maintain the slope _over_ the valley. The _Pont du Gard_ is Southern France is a still-existing triple-tiered example of this > **[Pont du Gard](https://en.wikipedia.org/wiki/Pont_du_Gard)** > > The Pont du Gard is an ancient Roman aqueduct bridge built in the first century AD to carry water over 50 km (31 mi) to the Roman colony of Nemausus (Nîmes). It crosses the river Gardon near the town of Vers-Pont-du-Gard in southern France. The Pont du Gard is one of the best preserved Roman aqueduct bridges. It was added to UNESCO's list of World Heritage sites in 1985 because of its exceptional preservation, historical importance, and architectural ingenuity. > The bridge has three tiers of a... ---
**Author:** ![Uncertain](https://avatars.discourse-cdn.com/v4/letter/u/6a8cbe/32.png) [@Uncertain](https://boards.straightdope.com/u/Uncertain)\ **Post date:** [January 7, 2011, 1:26pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/32 "2011-01-07T13:26:31Z")
> [@Schnitte](#): > > as long as one end of the line lies higher than the other, water will flow from the latter to the former And you’ve got yourself a perpetual motion machine. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [January 7, 2011, 2:12pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/33 "2011-01-07T14:12:09Z")
> [@CalMeacham](#): > > Romans didn’t use pipes to clear valleys – they built aqueducts on bridges to maintain the slope _over_ the valley. The _Pont du Gard_ is Southern France is a still-existing triple-tiered example of this > > [Pont du Gard - Wikipedia](http://en.wikipedia.org/wiki/Pont_du_Gard) When a valley was far too deep, they had the pipe go down and narrow and build pressure down hill and then have it flow up, but preserve overall end-to-end grade, too. Inverted siphons crossed river valleys in the Aqueduct of the Gier, one of four supplying Lyon. Huge arched structures were not built over all valleys. ---
**Author:** ![Bridget\_Burke](https://avatars.discourse-cdn.com/v4/letter/b/7cd45c/32.png) [@Bridget\_Burke](https://boards.straightdope.com/u/Bridget_Burke)\ **Post date:** [January 7, 2011, 2:28pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/34 "2011-01-07T14:28:22Z")
The Alamo thread on this board reminded me of the aqueduct in [San Antonio, Texas](http://www.waymarking.com/waymarks/WM4505_Mission_Espada_Aqueduct_San_Antonio_Tx). ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [January 7, 2011, 2:45pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/35 "2011-01-07T14:45:33Z")
> [@](#): > > When a valley was far too deep, they had the pipe go down and narrow and build pressure down hill and then have it flow up, but preserve overall end-to-end grade, too. > > Inverted siphons crossed river valleys in the Aqueduct of the Gier, one of four supplying Lyon. Huge arched structures were not built over all valleys. Most interesting. I had not heard of this before. On the other hand, it seems to be the exception, rather than the rule. I can’t find any other examples of such inverted siphons, but there are plenty of aqueduct bridges spanning valleys. And the very use of extended aqueducts running into Rome and other cities, rather than running water through underground pipes, shows that the Romans preferred to use unpressurized gravity flow to pressurinzed flow through pipes: When a valley was far too deep, they had the pipe go down and narrow and build pressure down hill and then have it flow up, but preserve overall end-to-end grade, too. > **[List of Roman bridges | Aqueduct bridges](https://en.wikipedia.org/wiki/List_of_Roman_bridges#Aqueduct_bridges)** > > 1.List of ancient architectural records § Bridges | > 2.List of Roman sites in Spain General overview > 1.Roman architecture | > 2.Roman engineering | > 3.Roman military engineering | > 4.Roman technology Other Roman building structures ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [January 7, 2011, 2:55pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/36 "2011-01-07T14:55:58Z")
Spoke too soon. Here’s a fascinating page with a listing of over 60 siphons (elsewhere he says 70. I certainly count more than 70), and pix from two other examples besides Lyon: > **[Siphons in Roman (and Hellenistic) aqueducts](http://www.romanaqueducts.info/siphons/siphons.htm)** > [@](#): > > The overview below lists some 60 Greek and Roman siphons. Elsewhere on this website literature was collected on more than 600 Roman and Greek aqueducts. This leads to the suggestion that 1 out of 10 aqueducts were equipped with a siphon. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [January 7, 2011, 3:30pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/37 "2011-01-07T15:30:54Z")
They used them when they really needed to. I’ve seen it noted that they didn’t like blowouts and leaks, so opted for them when it made sense. ---
**Author:** ![JoelUpchurch](https://avatars.discourse-cdn.com/v4/letter/j/f05b48/32.png) [@JoelUpchurch](https://boards.straightdope.com/u/JoelUpchurch)\ **Post date:** [January 7, 2011, 8:31pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/38 "2011-01-07T20:31:01Z")
The Romans often did the siphons as a series of smaller pipes, rather than a single large pipe to reduce the pressure and because they didn’t have the technology to reliably build larger pipes. The siphon across the river Garon had 18 pipes. They also preferred to have their aqueducts above ground to make it easier to find and repair leaks. There is an extensive discussion of aqueducts in **The Ancient Engineers** by L. Sprague De Camp, which is one of my favorite non-fiction books. ---
**Author:** ![Mk\_VII](https://avatars.discourse-cdn.com/v4/letter/m/5f9b8f/32.png) [@Mk\_VII](https://boards.straightdope.com/u/Mk_VII)\ **Post date:** [January 7, 2011, 9:25pm UTC](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602/39 "2011-01-07T21:25:33Z")
They would have wanted to avoid people tapping ground-level pipes to get their own private water supply upstream. [Previous page](https://boards.straightdope.com/t/why-did-the-romans-bother-to-build-aquaducts/566602.md?page=1)