Where sewer backups happen in Ottawa: 311 reports by ward, 2019–2025

Updated 2026-09-16

Seven years of City of Ottawa 311 records on basement flooding from sewer backups, ranked by ward, with the months they happen and what homeowners in the busiest wards can do.

What the numbers cover

From January 2019 to December 2025, Ottawa residents made 5,001 requests to 311 about sewer backups. Of those, 4,752 were filed as drain trouble with basement flooding and 249 as a backup after City sewer cleaning. The yearly count ranged from 620 in 2024 to 856 in 2025, the highest of the seven years.

Street and yard drainage is a different problem and is counted separately: 8,554 requests about catch basins, surface drainage, backyard flooding and blocked catch basin pipes. Water on a lawn or street is not the same as sewage coming up through a floor drain, so this guide ranks wards by backups only and shows drainage alongside.

The 12 wards with the most sewer backup reports since the 2022 ward change

Alta Vista leads with 335 backup reports, 14% of the 2,357 placed on the new ward map, and 16.6 per 1,000 households. College follows with 289 and Capital with 183. Together the top three hold 34% of reports.

The list is mostly older urban and inner-suburban wards: Alta Vista, College, Capital, Kitchissippi, River, Bay, Rideau-Rockcliffe and Knoxdale-Merivale. These are areas with many older homes, most built before backwater valves were standard. Newer suburbs file more drainage reports than backup reports.

Sewer backup 311 reports by ward, 15 November 2022 to 31 December 2025 (new ward boundaries)
Rank	Ward	2023	2024	2025	Backups since 15 Nov 2022	Drainage reports, same period	Backups per 1,000 households (approx.)
1	Alta Vista (Ward 18)	138	72	115	335	224	16.6
2	College (Ward 8)	102	72	101	289	151	12.9
3	Capital (Ward 17)	55	38	86	183	140	10.1
4	Kitchissippi (Ward 15)	55	38	63	167	108	7.3
5	River (Ward 16)	77	41	38	162	157	7.6
6	Bay (Ward 7)	43	39	55	149	147	7.0
7	Rideau-Rockcliffe (Ward 13)	39	42	58	145	109	7.0
8	Knoxdale-Merivale (Ward 9)	70	25	41	139	129	8.4
9	Rideau-Vanier (Ward 12)	35	44	45	129	95	4.5
10	Somerset (Ward 14)	31	28	43	107	136	4.2
11	Gloucester-Southgate (Ward 10)	18	18	33	71	101	3.7
12	Barrhaven West (Ward 3)	30	22	11	66	133	n/a (redrawn)

Before the ward change: 2019 to 2022

The old ward map, from January 2019 to 14 November 2022, gives the same leaders. Alta Vista had 318 backup reports (15.8 per 1,000 households), College had 292 (13.0) and Kitchissippi had 253 (11.1). Bay and Rideau-Rockcliffe came next with 209 and 206. For drainage, the suburban wards led: Gloucester-South Nepean had 415 reports and Cumberland 401.

When backups happen

Backups happen all year, and single storms drive the peaks. August has the most reports over the seven years (645, or 13%), but 258 of those came in August 2023 and 130 on one day, 10 August 2023. Spring is the other risk period: March and October each had 459 reports and April had 436, including 145 in April 2019, 67 of them on 15 April. February is the quietest month with 346.

Drainage reports follow the seasons more closely. May to August holds half of them (4,300 of 8,554), and December and January have 242 each.

What it means if you live in one of the top wards

If your home is in Alta Vista, College, Capital, Kitchissippi or River, especially an older house with a basement floor drain, assume a heavy rainstorm can push sewer water back into the basement. A backwater valve on the sanitary line is the main defence. A sump pump handles groundwater around the foundation and does not stop a backup.

The City's Residential Protective Plumbing Program pays part of the cost of a backwater valve, sump pump or storm lateral disconnection when the work is done with a permit. Check the program page for current amounts and eligibility before you book. Also check that your home insurance includes sewer backup coverage, and ask whether a valve lowers the premium. If you have already had a backup, a camera inspection of the lateral shows whether roots, a sag or a break are part of the problem.

Method

The source is the City of Ottawa 311 service request files on Open Ottawa, one file per year for 2019 to 2025, downloaded on 16 September 2026, with ward names from the Wards 2022-2026 layer and household counts from the City's mid-2021 population and household estimates by ward. The files hold 2,275,101 requests in total (2019: 356,715, 2020: 297,644, 2021: 299,245, 2022: 308,925, 2023: 321,193, 2024: 319,310, 2025: 372,069). 2 rows were skipped as malformed (one in 2024 and one in 2025, each an address with an unquoted comma that shifted the columns; neither was a topic covered here).

A request counts as a sewer backup when its description contains "Drain Trouble Basement Flooding" or "Backup From Sewer Cleaning". Drainage reports are those containing "Catchbasin Investigation", "Surface Drainage", "Backyard Flooding" or "Catch Basin Pipe Blocked", not counting discarded needle calls. Left out: road catch basin and maintenance hole calls (mostly covers and road repairs), sewer odours, spills, cave-ins, and lost keys or animals in sewers. 101 backup requests had no ward and appear only in the city totals. A 311 report is a call, not a confirmed backup, and many backups are never reported to the City.

Ward boundaries changed when the new council term began on 15 November 2022. Requests before that date are counted on the old 23 wards, and requests from that date on are counted on the new 24 wards; the 2022 figures in the new-ward table cover 15 November to 31 December only. The household estimates are on the old boundaries, so the rate per 1,000 households is exact for the old wards and only approximate for new wards that kept their number and name. Wards 1, 2, 3, 19, 21, 22 and 24 were redrawn or renamed, so they get no rate.