Talk:Combined sewer

article name and topic
this article should be called combined sewer or combined sewer system. it is about the system. the overflow aspect is a subordinate detail and in any case we need an article on the system before we can start discussing the overflow phenomenon. Phasechange 23:40, 30 September 2006 (UTC)

introductory paragraph
This paragraph was complex as written. Tried to simply so reader doesn't have to background knowledge to understand. Cleanedwater (talk) 19:51, 13 August 2009 (UTC)

design history
Added detail to first paragraph on where combined systems are located. Made sizing information more specific. Clarified that the devices are regulators.

combined sewer overflows
Existing definition was incorrect. CSO are not an apparatus, they are the flow of combined sewage discharged from the pipe. Cleanedwater (talk) 18:51, 14 August 2009 (UTC)

mitigation of CSO impacts
Added specific examples of how municipalities have mitigated CSO in Michigan. Modified paragraph on storage to discuss facilities that just provide storage. Added paragraph on retention treatment basins that store and treat combined sewage to prevent CSO.

Cleanedwater (talk) 20:24, 14 August 2009 (UTC) Discussion on screening and disinfection facilities could be added in the future.

Deleted information on discussion of New York basin and did not update because not familiar with it. Text says it provides mechanical treatment so it is not just a storage facility. However, it is not clear if it provides disinfection. The ability of the basin tanks to store a 100-year storm seems questionable since most municipalities cannot afford to design to this large of a storm event. Something may have been misinterpreted here. Reference to raw sewage flowing into a body of water is also incorrect since it is diluted, combined sewage that would overflow (that my even have been treated depending on how the basin operates). Deleted information is being stored here for future updating if desired:

As described above, in the initial setup, water would flow through the relief structure out into a body of water. In this new arrangement, the water would be diverted through a channel into a treatment building. Typically, only mechanical treatment (screening of solids) would be completed. The sewage which previously flowed into the water, would flow into a large storage tank, typically underground. That tank would have the capacity to hold runoff from all but the largest storms which occur once every 100 years or less. Once the storm passes, the facility's pumps would send the retained water back into the system to be treated under the normal dry-weather process. The result of this effort is the near elimination of raw sewage flowing into the body of water. An example of this type of system is currently being constructed for the New York City Department of Environmental Protection (NYCDEP) in Brooklyn at Paerdegat Basin.

Cleanedwater (talk) 20:24, 14 August 2009 (UTC)

Added globalize tag
I added a "globalize/USA" tag to this article because the article is mostly relevant to the United States, so I thought it needed a more global perspective. Combined_sewer Jarble (talk) 05:43, 18 March 2012 (UTC)

UK overflow/storm sewers
This section was tagged as needing a citation.

''There is in the UK a legal difference between a storm sewer and a surface water sewer. You do not have a right of connection to a storm sewer under section 106 of the Water Industry Act. These are normally the pipe line that discharges to a watercourse, downstream of a combined sewer overflow. It takes the excess flow from a combined sewer. A surface water sewer conveys rainwater; legally you have a right of connection for your rainwater to this public sewer. A public storm water sewer can discharge to a public surface water, but not the other way around, without a legal change in sewer status by the water company''

According to the law in question, this is 100% true.

(1)Subject to the provisions of this section—

(a)the owner or occupier of any premises, or

(b)the owner of any private sewer which drains premises,

shall be entitled to have his drains or sewer communicate with the public sewer of any sewerage undertaker and thereby to discharge foul water and surface water from those premises or that private sewer.

(2)Subject to the provisions of Chapter III of this Part, nothing in subsection (1) above shall entitle any person—

(a)to discharge directly or indirectly into any public sewer—

(i)any liquid from a factory, other than domestic sewage or surface or storm water, or any liquid from a manufacturing process; or

(ii)any liquid or other matter the discharge of which into public sewers is prohibited by or under any enactment; or

(b)where separate public sewers are provided for foul water and for surface water, to discharge directly or indirectly—

(i)foul water into a sewer provided for surface water; or

(ii)except with the approval of the undertaker, surface water into a sewer provided for foul water; or

(c)to have his drains or sewer made to communicate directly with a storm-water overflow sewer.

Source: http://www.legislation.gov.uk/ukpga/1991/56/part/IV/chapter/II/crossheading/communication-of-drains-and-private-sewers-with-public-sewers

72.200.151.13 (talk) 20:41, 29 August 2015 (UTC)


 * The value of the paragraph in question seems questionable to this article after reviewing the General interpretation section of the referenced law (which appears equivalent to the Definitions section of US law.)


 * The general interpretation of drain and lateral drain (seemingly equivalent to lateral in US usage) implies the former includes yard drainage and the latter typically include roof runoff and groundwater accumulations from cellars. Under US usage, yard drainage, roof runoff, and cellar groundwater would be collected only in combined sewers defined at 40CFR35.2005(b)(11) as a sanitary sewer and a storm sewer. Is this practice sufficiently widespread in the UK that most sewerage collection systems are functionally combined sewers?


 * Can someone provide a reference citation for a UK definition of combined sewer? Is the difference significant enough to require a separate article (or perhaps a separate section in this article) rather than the paragraph at issue?


 * Perhaps problems involving differing definitions of storm sewer or surface water sewer might better be addressed in the storm drain article. Alternatively, confusion over differing definitions of storm-water overflow sewer, disposal main, discharge pipe, or outfall line might better be addressed in the outfall article. Thewellman (talk) 22:45, 29 August 2015 (UTC)

Need better description of combined sewer at the start
The article jumps straight into the topic of CSO. Should we not first explain a bit better what a combined sewer is before talking about CSO? Should there be two distinct pages, one on combined sewer and one on combined sewer overflow? Also there is probably quite a bit of overlap with the article on sanitary sewer overflow.EvM-Susana (talk) 09:40, 2 September 2015 (UTC)


 * The article structure you find confusing has resulted largely from your reorganization to place the history near the end of the article. I suggest the guideline for such article structure should be disregarded for this article, since sewer history is so important to understanding the definition of combined sewers and why they evolved as they have.


 * I would prefer to leave CSOs in this article -- although integrated into the history to explain what was initially an expected part of sewer function has become less acceptable with changing environmental perceptions. Perhaps the CSO confusion might be clarified by determining if the term combined sewer overflow describes an event in American English or a structure in British English.


 * I suggest adding the combined sewer overflow information to the sanitary sewer overflow article would unnecessarily increase confusion about the difference between sanitary sewers and combined sewers. The causes of the two overflows are quite different.  Combined sewer overflow is an expected event based on frequency of runoff flows exceeding treatment facility design capacity; while sanitary sewer overflows are sewer system malfunctions caused by obstructions, infiltration/inflow, or exceeding sewer system design capacity.Thewellman (talk) 16:30, 2 September 2015 (UTC)


 * We have suggested to put the history section towards the end for all projects tagged under the WikiProject Sanitation... I think it helps the reader to quickly grasp a new article if the headers follow a similar order this time. If it works for all the other articles, it should also work for this one. I see your point though and have therefore moved that part from the history section that explains the reasons for why it's combined back to the front. Note that the history section also has quite a bit of overlap with the history section of the sanitary sewer article. This could be improved. (actually I have to correct myself, the history section on sanitary sewer is quite short. I would have thought "sanitary sewer" should be the overarching term and then there is combined sewer versus separate sewers underneath that term (the distinction between historic (=combined sewer) and modern (=separate sewer) is not really valid, e.g. in Australia and I thought in Germany as well combined sewers were or are still built until quite recently or even nowadays). - About CSO and SSO, when you look on the page of SSO it states there "Sanitary sewer overflow (SSO) is a condition in which untreated sewage is discharged into the environment prior to reaching sewage treatment facilities. In Europe the term Combined Sewer Overflow (CSO) is often used." This makes it seem like the distinction that you made (while logical) is not used like that by all people. We should clarify this issue on both pages. EvM-Susana (talk) 21:44, 2 September 2015 (UTC)


 * I understand combined sewers are fairly common in cities sewered before the second world war; and few of these cities have rebuilt their inner city infrastructure to separate sewage from stormwater runoff; although more recent suburban residential developments may have separate sanitary sewers to minimize combined sewer overflow events. The defining difference between combined sewer overflows and sanitary sewer overflows is the location of the overflow event.  Sewage treatment plants serving a combined sewer system are typically built with a bypass structure to avoid flooding or otherwise damaging sewage treatment plants. This bypass may be identified as a combined sewer overflow in British English; and the bypass structure is the location of combined sewer overflow events.  Sanitary sewer overflows occur at random low spots in the collection systems and may cause sewage to flood residential structures or flow down city streets rather than being routed through a conduit designed to avoid damage and disease risks prior to reaching natural waterways. I will work on finding reference citations to add this difference to the SSO article and to the CSO portion of this article. Thewellman (talk) 05:21, 3 September 2015 (UTC)
 * Sounds good. I am not an expert on this but I think in Germany for example we tend to have combined sewer systems but nowadays more and more focus on local rainwater management (many new houses have cisterns) and local infiltration of rainwater. In that case, there may not be a need for having two sewers (one for sewage and one for rainwater). Incidentially, a collague sent me this link about history of wastewater treatment. It links to a book chapter, I am not sure if it's normally available without having to pay for it but in any case here is the link to the pdf file: http://www.bvsde.paho.org/bvsacd/leeds/cooper.pdf You might be able to draw from it.EvM-Susana (talk) 08:27, 3 September 2015 (UTC)
 * There is a comprehensive report on CSOs and SSOs that was prepared by USEPA. "Report to Congress: Impacts and Control of CSOs and SSOs." August 2004. http://water.epa.gov/polwaste/npdes/cso/2004-Report-to-Congress.cfm I think you'll find everything you need in there. Chapter 1 provides a basic introduction to CSOs & SSOs. Moreau1 (talk) 00:52, 4 September 2015 (UTC)

I have my doubts about the section on Smart Infrastructure
I think the new section on "smart infrastructure" is doubtful in the sense that laypersons would find it hard to understand. The sources cited are pretty much primary research papers, aren't they? If not, can you give some actual examples (for cities where this has been implemented), ideally with Wikilinks to other pages where this is described more. To me it sounds a bit like wishful thinking - something that could be implemented but rarely has so far. But would be happy to be convinced otherwise if you make further clarification edits? EvMsmile (talk) 00:15, 30 October 2015 (UTC)

External links modified
Hello fellow Wikipedians,

I have just added archive links to 1 one external link on Combined sewer. Please take a moment to review my edit. If necessary, add after the link to keep me from modifying it. Alternatively, you can add to keep me off the page altogether. I made the following changes:
 * Added archive https://web.archive.org/20061111132442/http://www.thompsonrpm.com/screens/pdf/TRPM-TN002.pdf to http://www.thompsonrpm.com/screens/pdf/TRPM-TN002.pdf

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External links modified
Hello fellow Wikipedians,

I have just added archive links to 1 one external link on Combined sewer. Please take a moment to review my edit. If necessary, add after the link to keep me from modifying it. Alternatively, you can add to keep me off the page altogether. I made the following changes:
 * Added archive http://web.archive.org/web/20130515150901/http://www.seattle.gov/mayor/media/PDF/120521PR-SPU-CSO-FAQs.pdf to http://www.seattle.gov/mayor/media/PDF/120521PR-SPU-CSO-FAQs.pdf

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Creating new page on CSOs?
Im am wondering if it makes sense to create a new page on Combined sewer overflow analogous to Sanitary sewer overflow. Subsections on CSO are quite large...Mll mitch (talk) 09:41, 14 April 2016 (UTC)
 * Would the new combined sewer overflow article describe the structures or describe the events? It would be important to reach agreement about nomenclature prior to breaking part of this subject out into another article. Thewellman (talk) 16:33, 14 April 2016 (UTC)
 * I don't know - perhaps describe both? EvMsmile (talk) 12:04, 15 April 2016 (UTC)
 * I suggest a description of the infrastructure installed where combined sewers are designed to overflow (called storm water regulators in American English) should be retained in the combined sewer article focused on infrastructure. If a new article is created to describe the nature and consequences of combined sewer overflow events, it should begin with a disambiguation hatnote explaining the regulator function. Wikipedia administrator Diannaa recently informed me the talk page of the new article should include a properly formatted copied template; and the edit summaries for transferred material should be in the following form: copied content from page name ; see that page's history for attribution Thewellman (talk) 18:32, 15 April 2016 (UTC)
 * Thanks for this. Sounds good. I don't know enough about these things, but am hoping that others will move this forward. Which new artcle did you mean in your sentence: "Wikipedia administrator Diannaa recently informed me the talk page of the new article should include a properly formatted copied template" ?EvMsmile (talk) 13:13, 17 April 2016 (UTC)
 * I mentioned this because I, too, was a bit surprised. As I understand the guidance document, a completed copied template should be included on the talk page of the destination article whenever material is copied or moved from one article to another. As I understood this proposal was to create a new combined sewer overflow article by transferring text from the existing combined sewer article, I believe the destination article in this case would be the new combined sewer overflow article. The following text is copied from the administrator's message on my talk page: Thewellman (talk) 14:53, 17 April 2016 (UTC)
 * "While you are welcome to re-use Wikipedia's content, here or elsewhere, Wikipedia's licensing does require that you provide attribution to the original contributor(s). When copying within Wikipedia, this is supplied at minimum in an edit summary at the page into which you've copied content. It is good practice, especially if copying is extensive, to also place a properly formatted copied template on the talk pages of the source and destination.... You can read more about the procedure and the reasons at Copying within Wikipedia."
 * "describe the structures or describe the events" - Here CSO events are illegal, thus CSO structure would be preparation for committing a crime (and therefore also a crime in itself). Is that legal in the US?! Please put in a sentence about the legal situation in the US, thank you. 2A01:C23:6DFC:8200:6D58:E25C:DF79:ADCA (talk) 19:50, 9 July 2022 (UTC)
 * You didn't mention where overflows are illegal. The legal situation in the United States varies somewhat with the age of the sewered area.  New construction usually assigns a high priority to preventing overflows, but densely built older infrastructure often includes earlier combined sewers (with CSO structures) where overflows may be tolerated as preferable to the cost of, or damage caused by, retrofitting separate sewer systems into historic districts. Thewellman (talk) 21:09, 9 July 2022 (UTC)

Suggestion to move the part on ancient sewers to the history article
I am wondering if we could move (or shorten and link) the part on "ancient sewers" (https://en.wikipedia.org/wiki/Combined_sewer#Ancient_sewers) rather to history of water supply and sanitation. What is described there fits in my opinion more in a history article and less with an article that is trying to described what "combined sewers" are all about. The information would not be lost - the reader would be re-directed across. It would make this article more focussed and avoid that the same information appears in two articles. - I would only leave the part here that really deals with what we think of nowadays as "combined sewers" i.e. those pioneered in the UK etc. EvMsmile (talk) 12:04, 15 April 2016 (UTC)
 * I agree. I transfered information about ancient sewers to History_of_water_supply_and_sanitation where I think it fits better. I also think the history section of this article could be improved through contextualizing more history (examples) and the evolvement of combined sewers.--Mll mitch (talk) 08:42, 18 April 2016 (UTC)

History section still needs further work
I've streamlined the history section a bit more, taking out what I found unnecessary detail about the lenghts and directions of sewers in London, where this info is anyhow there in identical wording in this article: history of water supply and sanitation. Rather than focussing here only on London and Paris we should explain:
 * how did combined sewers really work before everyone had indoor plumbing
 * where and when did people first move away from combined sewers to sanitary sewers and why?
 * what are more recent developments in combined sewers, do they still get built nowadays and why

I.e. the historical developments from combined sewers to split systems needs to be made clearer. I would do it myself if I had the information at my fingertips, but I don't. EvMsmile (talk) 06:38, 22 April 2016 (UTC)
 * There is a reference already cited in the article than answers your questions at a basic level: Burrian et al, "The Historical Development of Wet-Weather Flow Management" (1999). As discussed in the Burrian article, the majority of the engineering profession had recommended, until the 1930s-1940s, that urban areas be built with combined sewer systems. As communities grew, the prospect of building additional sewage treatment plants with sufficient capacity to treat the corresponding increase in stormwater was deemed to be not cost-effective. Therefore, since that time, new communities (often these have been suburban areas) were built with separate storm sewers. See pp. 7-9. Burrian also has a brief discussion of contemporary thinking (c. 1999) about the possible construction of new combined sewer systems in certain situations (p. 16). The references cited provide additional details. Moreau1 (talk) 04:32, 24 September 2016 (UTC)
 * Could you please add this information to the article? I think that would be good. EvMsmile (talk) 15:06, 24 October 2016 (UTC)
 * I have moved the content from the history section that was about sewers in general to history of water supply and sanitation and then replaced it with an excerpt (we could also transclude more paragraphs if we like). I felt it's better to have the general sewer history stuff (London, crowding, cholera, etc) in one place rather than repeated over several articles. It that information from the Burrian article about specifically how sanitary sewers became more preferred over combined sewers hasn't yet been added this should still be done. Actually, I think it's already in there but I didn't see it at first; I have now renamed that section to "Development" but I am unsure if it should become part of the "History" section? EMsmile (talk) 14:03, 25 August 2021 (UTC)