Where Columbus water comes from, and what that means for a shower
A shower in Columbus runs on one of three things: the Scioto River, Big Walnut Creek, or a field of wells in the Scioto River valley. Which one depends on the address, because three treatment plants divide the city between them and they do not all run the same process. This page follows the water through the reservoirs and the plants, back through the 1904 typhoid outbreak and the 1908 plant that answered it, out to who is on Columbus water and who is not, and forward to the fourth plant now being built. Where the city's own documents disagree, the page says so.
Last updated September 2026 · Figures are the city's, Ohio EPA's and the US Geological Survey's, read September 2026 · No prices on this page; the Estimate Builder carries those · Part of the knowledge base
Where a Columbus shower's water starts
The city's own water quality report says the system uses surface water from the Scioto River and Big Walnut Creek, together with ground water pumped from sand and gravel deposits of the Scioto River valley. Two rivers and a well field is the whole of the supply.
The rivers do not run straight to a treatment plant. Reservoirs stand in between, and there are four of them rather than the three most people can name. Three are in-stream reservoirs the city maintains: Hoover on Big Walnut Creek, and Griggs and O'Shaughnessy on the Scioto. The fourth almost never comes up: the John R. Doutt Upground Reservoir, an off-stream basin in Delaware and Union counties near Richwood, completed in 2014. A fifth body of water in the picture is not the city's at all. Columbus holds rights to draw from Alum Creek Reservoir to supplement Hoover in dry periods, and its own reservoir brochure says plainly that it does not own or operate it.
The three plants, and what each one serves
Three treatment plants stand between those sources and the tap, and an address decides which one. The Dublin Road Water Plant treats Scioto River water and serves downtown Columbus and the western and southwestern parts of Franklin County. The Hap Cremean Water Plant on Morse Road treats Hoover Reservoir water out of Big Walnut Creek, with supplemental water pumped from Alum Creek Reservoir in dry periods, and serves what the city's 2024 annual report calls the largest area, including northern and northeastern Franklin County and The Ohio State University. The Parsons Avenue Water Plant treats well water and serves southeastern Franklin County. Between them, by a figure Ohio EPA and the city both publish, the three supply an average of about 145 million gallons of drinking water a day.
| Plant | Where its water comes from | In service | Serves | Rated capacity, as the city states it |
|---|---|---|---|---|
| Dublin Road Water Plant | The Scioto River, by way of Griggs and O'Shaughnessy reservoirs and the John R. Doutt Upground Reservoir | 1975, on the ground where the 1908 plant stood | Downtown Columbus and the western and southwestern parts of Franklin County | 80 million gallons per day |
| Hap Cremean Water Plant, Morse Road | Hoover Reservoir on Big Walnut Creek, with supplemental water pumped from Alum Creek Reservoir in dry periods | Opened 1956, took its present name in 1988 | The largest area, including northern and northeastern Franklin County and The Ohio State University, in the words of the city's 2024 annual report | 125 million gallons per day |
| Parsons Avenue Water Plant | Wells in the Scioto River valley | 1984 | Southeastern Franklin County | 50 million gallons per day |
Those are rated capacities as the city's 2024 annual report states them, not what the plants treat on a given day. An older set of production figures is also in circulation, and the two should never be read side by side: putting them in one line makes the plants look as though they shrank. All three service areas are the city's 2024 annual report's own words.
The difference between the plants is not only geographic. The city's water quality report says that when groundwater is used, screening, initial sedimentation, ozone and ultraviolet disinfection are not needed, so the Parsons Avenue plant leaves out several steps the two river plants run. A shower on the southeast side and a shower downtown are both on Columbus water, and the water in them did not start in the same place or go through the same process.
How Columbus got here, in order
The city says its first water supply system, a well and a pumping station, went into operation on May 1, 1871. That date comes from city documents; no independent publisher confirming it was found for this page.
What happened next is the reason the rest of this page exists. A physician later recounted, in the Ohio Archaeological and Historical Quarterly, that an explosive outbreak of typhoid fever occurred in Columbus in February 1904. His account describes a city with two water supplies at the time: one drawn raw from the Scioto River, the other from wells along Alum Creek. The same account traces the outbreak to a broken bulkhead at the Columbus State Hospital that sent sewage into the Scioto opposite the water intake. It also gives a count of cases and of deaths, which this page does not repeat, because the account states no case definition and no population base.
Work on Griggs Dam began in 1904 and the reservoir went into service in 1905, supplying the plant on Dublin Road that Griggs still supplies. The eleventh edition of the Encyclopaedia Britannica, published in 1911, recorded that the city had completed works for filtering and softening its water supply in 1908. The city's own account of that plant is the sentence that gets repeated most: it says the 1908 plant, known internationally as the Columbus Experiment, "was the first water plant to combine filtration and water softening." Notice what the city's sentence does not carry. There is no geographic qualifier in it, not "in the United States" and not "the largest," and any version that has one has had it added.
The city credits Charles Hoover with the co-discovery of a water softening process using lime and soda ash, and describes his brother Clarence as the chief chemist and bacteriologist of sewage treatment. It says their work reduced the number of deaths from typhoid in Columbus in the early twentieth century. It attaches no figure to that sentence, and this page adds none.
The reservoirs arrived in a slow sequence after that. O'Shaughnessy Reservoir, in Delaware County near Powell, was built in 1925 to add water for the Dublin Road plant. Hoover Reservoir was built on Big Walnut Creek near Westerville, across Franklin and Delaware counties, and here the city's own documents disagree with each other: its reservoir brochure says 1955, its historical timeline says 1953, and the Columbus Metropolitan Library's record of the dam says the project was completed and dedicated in 1955 and the dam officially opened in 1958. Two of the three land on 1955, which is what this page prints. The library's record also says the reservoir is named for two brothers, Charles P. Hoover and Clarence B. Hoover, for their careers with the Columbus waterworks. The same Hoovers.
The plants are younger than the water they treat. By the city's own account, the Hap Cremean Water Plant opened in 1956 on Morse Road and took its present name in 1988; city records put the Dublin Road plant standing today in service in 1975, on the ground where the 1908 plant stood, which had itself replaced the works of 1871. The Parsons Avenue plant went into service in 1984, and this is the second place the city's documents disagree: one city page gives 1979 for that plant, which the city's own timeline records as the year construction began, five years before it started up.
Then a dry year made the argument for storage. The city's historical timeline records that a severe drought in 1988 depleted the reservoirs and that water use restrictions were imposed on customers. The Doutt reservoir and the standing rights on Alum Creek are both answers to a year like that one.
Who is on Columbus water, and who is not
Columbus does not serve only Columbus. The department, called the Department of Public Utilities until it became Columbus Water and Power on May 14, 2025, provides water and sewer service to dozens of surrounding communities under contract. This page prints no count of them, for a plain reason: the department's own documents give three different numbers. Three of its own recent documents give three different totals, and they mix water contracts with sewer contracts, so none of them is printed here as the number. The population figure is steadier. The 2024 annual report puts the estimated service population at about 1.4 million, while Ohio EPA's assessment of the new plant puts the population inside Columbus itself at approximately 900,000.
The city also publishes a list of places it does not serve, and for a homeowner that list is the more useful of the two. It names Canal Winchester, Pickerington, parts of Westerville, and townships such as Blendon that Aqua Ohio serves. Westerville appears on both lists, in different parts of the same city, which is the clearest sign available that the boundary follows addresses rather than city names. Ohio EPA carries Westerville City as its own public water system, number OH2503411, drawing on Alum Creek, separate from the Columbus Public Water System, number OH2504412.
Delaware County addresses are largely on Del-Co Water Company instead, as the hardness page sets out, a separate utility whose own page says its primary sources are the Olentangy River, O'Shaughnessy Reservoir and Alum Creek Reservoir. A Delaware County house can be drinking water that started in the same reservoir as a Columbus house and passed through a different utility's plant. Outside all of those systems a house is on a private well, which is a different set of questions with a page of its own. Hardness is the part of this a shower actually feels, and each utility's published figures sit on the hardness page rather than here. Which utility serves each town in the service area is on the providers page, and what the city's annual report measures, PFAS included, is on the water quality report page.
What that means for a shower today
Columbus still softens its water at the plant, which is the direct descendant of what happened in 1908. The city's water quality report says soda ash or caustic soda and hydrated lime are added to remove the calcium and magnesium ions responsible for hardness.
Chlorine is the disinfectant. The same report says chlorine is used as the primary and secondary disinfectant to kill disease-causing organisms, and that ultraviolet light disinfection is used for additional disinfection at both the Dublin Road and Hap Cremean plants. It is worth saying what that report does not say. It never uses the word chloramine, and it tabulates its own results under the heading Total Chlorine.
Fluoride is added as well, and the city says only that it is added as required by the State of Ohio. It names no statute and gives no start year more precise than a decade, so no start year is printed here.
The city also adds zinc orthophosphate, which it describes as a food grade additive, and adjusts the water's pH so that the treated water is less corrosive. That is corrosion control, and it is aimed at pipe rather than at water. It is also the point where the city's part of the system meets the house's: what the supply pipe inside a house is made of is the homeowner's to know, and it is the subject of a neighboring page.
On lead, this page prints the city's own words and adds nothing to them. Columbus Water and Power says the lead concentration in the drinking water leaving its plants is below the level of detection, and that most homes in the Columbus area do not have lead service lines. In 2024 the city established a Lead Service Line Replacement Program aimed at removing all public and private lead and galvanized service lines within the city; its own documents give more than one finish year for that work, so none is printed here, and the supply pipes page carries the detail. A homeowner who wants to know about one address rather than about the area can look that address up in the city's service line inventory.
Two of the three sources are open water, and open water changes temperature with the year. The US Geological Survey's gauge in Hoover Reservoir recorded monthly mean water temperatures of about 1.7 degrees Celsius, roughly 35 degrees Fahrenheit, in January 2026, and about 28.3 degrees Celsius, roughly 83 degrees Fahrenheit, in July 2025. Read that for what it is: a measurement in the reservoir, not at anybody's tap. No published figure was found for the temperature of cold water at a Columbus tap in any season, and none is claimed here. The plain inference, and it is an inference, is that the cold side of a shower valve is colder in February than in August, which is why a handle set in the same place does not give the same shower in both months. The valve doing that mixing has its own page.
The fourth plant, now being built
Columbus is building a fourth water plant. The city's project site calls it the Home Road Water Plant and says it is being built along the Scioto River in Delaware County, drawing from O'Shaughnessy Reservoir; Ohio EPA, in its environmental assessment, calls the same project the Fourth Water Plant. It is designed to add 48 million gallons a day to the system.
The reason is arithmetic rather than alarm. Ohio EPA's assessment says that without more capacity the Columbus service area faces a 35 million gallon a day deficit of treated water by 2050, measured against maximum day demands, with a projected 2050 service area population of 1.7 million.
The dates in circulation disagree, and both are worth having. The city's project site says construction of the water plant facility is scheduled to start in late 2026 and that the plant is anticipated to be completed by early 2033. Ohio EPA's assessment, dated January 2025, recorded a goal of bringing the new facility online by the end of 2030. The city's project site is the newer document and its dates are the ones this page prints; the earlier target is here so that a reader who meets it somewhere else knows which is which.
None of that changes a bathroom this year. It does say that the water in a Columbus shower is planned decades ahead, by a system that has been supplying this city since 1871.
The short version. A Columbus shower runs on the Scioto River, on Big Walnut Creek, or on wells in the Scioto valley, treated at one of three plants: Dublin Road, Hap Cremean or Parsons Avenue. Four reservoirs hold the surface water, and a fifth, Alum Creek, belongs to somebody else. A typhoid outbreak in 1904 was traced to sewage reaching the river beside the intake, and the city says the 1908 plant that followed was the first to combine filtration and water softening. The water is still softened, disinfected and treated for corrosion at the plant, and a fourth plant is going up in Delaware County. Every figure here belongs to the city, to Ohio EPA, to the US Geological Survey or to a library.
Sources
Every figure, date and quotation on this page comes from one of these documents, read on the date given. Where two of them disagree, the page says so.
- Columbus Water and Power, City of Columbus, 2025 Drinking Water Consumer Confidence Report, 2026; read September 2026.
- Ohio Environmental Protection Agency, Ohio Public Water Supply Lakes, undated; read September 2026.
- Columbus Water and Power, City of Columbus, Public Utilities Annual Report 2024, 2025; read September 2026.
- Columbus Department of Public Utilities, City of Columbus, Facts on Columbus Water Reservoirs, undated; read September 2026.
- City of Columbus, Columbus Water Supply Historical Timeline, undated; read September 2026.
- Ohio Environmental Protection Agency, Finding of No Significant Impact and Environmental Assessment, City of Columbus Fourth Water Treatment Plant, Site Preparation and Electrical Substation, January 6, 2025; read September 2026.
- City of Columbus, Water Treatment History, undated; read September 2026.
- Ohio History Connection, Ohio Archaeological and Historical Quarterly, Notes on the Prevention of Communicable Diseases in Columbus, 1890 to 1945, by Herbert M. Platter, M.D., volume 57, pages 393 to 397, undated; read September 2026.
- Encyclopaedia Britannica, eleventh edition, Columbus (Ohio), 1911; read September 2026.
- Delaware County Historical Society, Landmarks of Delaware County: O'Shaughnessy Dam, undated; read September 2026.
- Columbus Metropolitan Library, Aerial view of Hoover Dam and Reservoir, Columbus Memory collection, undated; read September 2026.
- City of Columbus, News Release: Department of Public Utilities Transforming into Columbus Water and Power, May 14, 2025; read September 2026.
- Columbus Water and Power, City of Columbus, Water and Sewer Contract Communities, undated; read September 2026.
- Del-Co Water Company, Del-Co's Water Sources, undated; read September 2026.
- US Geological Survey, National Water Information System, monthly statistics, Hoover Reservoir at Central College OH, site 03228400, retrieved September 5, 2026; read September 2026.
- Columbus Water and Power, City of Columbus, Columbus Fourth Water Plant, frequently asked questions, undated; read September 2026.
- Ohio Revised Code, codes.ohio.gov, Section 6109.20, Maintaining fluoride content of public water supply, effective December 14, 1978; read September 2026.
Common questions
Where does Columbus tap water come from?
From two rivers and a well field. The city's own water quality report says the system uses surface water from the Scioto River and Big Walnut Creek, together with ground water pumped from sand and gravel deposits of the Scioto River valley. Four reservoirs hold the surface water: Hoover on Big Walnut Creek, Griggs and O'Shaughnessy on the Scioto, and the John R. Doutt Upground Reservoir in Delaware and Union counties, completed in 2014. A fifth, Alum Creek Reservoir, is not owned by the city, which holds rights to draw from it to supplement Hoover in dry periods.
How many water treatment plants does Columbus have?
Three, with a fourth being built. The Dublin Road Water Plant treats Scioto River water and, by the city's 2024 annual report, serves downtown Columbus and the western and southwestern parts of Franklin County. The Hap Cremean Water Plant on Morse Road treats Hoover Reservoir water out of Big Walnut Creek and, by the same annual report, serves the largest area, including northern and northeastern Franklin County. The Parsons Avenue Water Plant treats well water and serves southeastern Franklin County. The same annual report rates the three at 80, 125 and 50 million gallons a day, and Ohio EPA puts their combined average at about 145 million gallons of drinking water a day.
Is Columbus tap water river water or well water?
Both, depending on the address. Two of the three plants treat surface water: Dublin Road takes the Scioto River, and Hap Cremean takes Big Walnut Creek by way of Hoover Reservoir. The third, Parsons Avenue, draws from wells and serves southeastern Franklin County. The city's water quality report says that when groundwater is used, screening, initial sedimentation, ozone and ultraviolet disinfection are not needed, so the well plant leaves out several steps the river plants run. Saying that Columbus is on river water is true of most of the city and not all of it.
Why is the 1908 Columbus water plant called the Columbus Experiment?
Because of what it combined. The City of Columbus says the 1908 plant on the Scioto, known internationally as the Columbus Experiment, was the first water plant to combine filtration and water softening. That is the city's own wording, and it carries no geographic qualifier: it does not say in the United States, and it does not say the largest. The 1911 Encyclopaedia Britannica recorded that the city had completed works for filtering and softening its water supply in 1908. The plant followed an outbreak of typhoid fever in Columbus in February 1904.
Does Westerville have its own water system?
Yes. Ohio EPA lists Westerville City as its own public water system, number OH2503411, drawing on Alum Creek, separate from the Columbus Public Water System, number OH2504412. Columbus complicates the picture: the city's own list of contract communities names parts of Westerville among the places it serves and parts of Westerville among the places it does not. That is the honest answer for a homeowner anywhere near the edge of the city. The boundary follows addresses rather than city names, and the utility that bills an address is the one that can say which system it is on.
What does Columbus add to its drinking water?
By the city's own water quality report: soda ash or caustic soda and hydrated lime to remove the calcium and magnesium that make water hard, chlorine as the primary and secondary disinfectant, ultraviolet light for additional disinfection at the Dublin Road and Hap Cremean plants, fluoride as required by the State of Ohio, and zinc orthophosphate with a pH adjustment to make the treated water less corrosive. Ohio Revised Code section 6109.20 requires a public water system to keep fluoride between eight-tenths and one and three-tenths milligrams per liter where the natural level is lower.
Why is Columbus building a fourth water plant?
To add capacity before the system runs short. Ohio EPA's environmental assessment says that without it the Columbus service area faces a 35 million gallon a day deficit of treated water by 2050, against a projected service area population of 1.7 million. The plant is designed to add 48 million gallons a day. The city's project site calls it the Home Road Water Plant, says it is being built along the Scioto River in Delaware County, and schedules construction to start in late 2026 with completion in early 2033; the Ohio EPA assessment of January 2025 recorded an earlier goal of the end of 2030.
Does Columbus water change temperature with the seasons?
The source does, measurably. The United States Geological Survey gauge in Hoover Reservoir recorded monthly mean water temperatures of about 1.7 degrees Celsius, roughly 35 degrees Fahrenheit, in January 2026, and about 28.3 degrees Celsius, roughly 83 degrees Fahrenheit, in July 2025. That is a measurement in the reservoir and not at a tap; no published figure was found for the temperature of cold water arriving at a Columbus tap in any season, so none is claimed. The plain inference is that the cold side of a shower valve is colder in February than in August.
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