A Pump House Disguised as a Cottage
The Sanjo City Waterworks Bureau Osaki Water Purification Plant Intake Pump Station Pump House (三条市水道局大崎浄水場取水ポンプ場ポンプ室) is a 1933 intake building on the east bank of the Igarashi River in Nakashin, Sanjo City, Niigata Prefecture, and it was listed as a Registered Tangible Cultural Property on October 28, 2011. Sanjo's water supply begins here, where river water is drawn up and sent inland to the treatment works.
It is a single-storey timber building, 13.7 meters by 7.3 meters, under a gabled sheet-metal roof. A small gabled porch projects at the front and a hip-roofed annex at the back. The walls are finished in mortar.
Nothing about the exterior says pump. The Agency for Cultural Affairs describes it as looking like a neat small house, and the Niigata branch of the Japan Society of Civil Engineers says much the same. Inside, at the center of the floor plan, sits an intake well 5.6 meters across. A cottage skin wrapped around a machine room with a well in its heart is what makes this building worth a detour.
Why an Architect Bothered
The Sanjo City Waterworks Bureau Osaki Water Purification Plant Intake Pump Station Pump House stands on its own below the levee, roughly 350 meters west of the treatment works, where anyone walking from town to the river would see it.
Sanjo City explains that the plant's process structures, the filters and reservoirs, were left plain, while the buildings that people see were given elegant, original designs. This pump house heads that list. Its designer was Hasegawa Tatsuo, an architect with a practice in Niigata city.
Building a small house rather than a machine shed on the riverbank reads as a deliberate choice to make the new waterworks feel like part of everyday town life. Together with the intake station gate just to the east, the pump house shapes a historic riverside scene.
What to Look For
Start with the roofs. The main gable, the smaller porch gable and the hipped annex behind step down in size, and from the front the porch gable echoes the main one. That echo is what makes the building read as domestic.
The city's reference photograph is taken from the northeast, the angle that best shows the porch against the long body of the building. You cannot see the intake well from outside, but knowing that a 5.6-meter well sits at the center explains the building's depth.
Sanjo City's water division says the raw water today is river-bed groundwater collected through a perforated pipe 410 meters long buried under the river. The intake method may have changed since 1933, and the city does not say what equipment the building now houses.
Visiting
The interior of the Sanjo City Waterworks Bureau Osaki Water Purification Plant Intake Pump Station Pump House is closed. The building lies outside the main plant below the Igarashi River levee, so even when the treatment works open for cherry blossom season, check with the city whether the intake station is included.
For the exterior, stand to the northeast to take in the porch and the long body together; the intake station gate stands just to the east and fits in the same frame. Directions and opening conditions are collected on the Sanjo City Waterworks Bureau Osaki Water Purification Plant page.
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Q&A
- When was the Osaki Water Purification Plant intake pump house built?
- It was completed in 1933 and listed as a Registered Tangible Cultural Property on October 28, 2011, along with eleven other structures of the plant.
- What does the Osaki intake pump house look like?
- A single-storey timber building, 13.7 meters by 7.3 meters, with a gabled sheet-metal roof, a gabled front porch and a hipped rear annex. It looks like a small house, but it holds an intake well 5.6 meters across.
- Can you go inside the Osaki Water Purification Plant intake pump house?
- No. The interior is not open. It stands outside the main plant, so ask the Osaki plant office (0256-38-3539) whether it is included in the spring opening.
- Who designed the Osaki Water Purification Plant intake pump house?
- The buildings of the plant were designed by Hasegawa Tatsuo, an architect based in Niigata city, while the hydraulic scheme was supervised by the waterworks engineer Moniwa Chūjirō.
- How far is the intake pump house from the Osaki treatment works?
- About 350 meters to the west, on the east bank of the Igarashi River, with Route 289 in between.
Basic Information
| Name | Sanjo City Waterworks Bureau Osaki Water Purification Plant Intake Pump Station Pump House |
|---|---|
| Location | 316 Nakashin, Sanjo City, Niigata Prefecture |
| Designation | Registered Tangible Cultural Property (Building) |
| Year Designated | Registered 2011/10/28 (Heisei 23) |
| Quantity | 1 building |
| Dimensions | Single-storey timber building with sheet-metal roof, 13.7 meters by 7.3 meters, building area 132 square meters |
| Owner | Sanjo City Waterworks |
| Public Access | Interior closed; stands outside the main plant on the east bank of the Igarashi River, so check access in advance |
References
- Cultural Heritage Database: Sanjo City Waterworks Bureau Osaki Water Purification Plant Intake Pump Station Pump House (Agency for Cultural Affairs, in Japanese)
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00008834
- Registered Tangible Cultural Property: Sanjo City Waterworks Bureau Osaki Water Purification Plant (Sanjo City, in Japanese)
- https://www.city.sanjo.niigata.jp/soshiki/shimimbu/shogaigakushuka/bunkazai/bunkazai/1740.html
- Sanjo City Waterworks Bureau Osaki Water Purification Plant (Japan Society of Civil Engineers, Niigata branch, in Japanese)
- https://jsce-niigata.com/introduction/article/049/art049.html
- How tap water is made (Sanjo City Water and Sewerage Division, in Japanese)
- https://www.city.sanjo.niigata.jp/soshiki/kensetsubu/jogesuidoka/jousuidonituite/jousuijo/4621.html
Last verified: 2026.09.25
