Kojima Seisakusho

What Kojima Seisakusho does

Kojima Seisakusho Co., Ltd. (株式会社小島製作所) is a Nagoya-headquartered, privately held Japanese manufacturer founded in 1919 that designs, produces, and sells building drainage equipment and system joints. The company's product portfolio is anchored by the CORE single-pipe drainage system, which uses internal guide swirls to move water efficiently through a single stack rather than conventional multi-pipe layouts; this system is described as holding high market share in its category and was specified in landmark projects such as the 2011 Tokyo Skytree. Complementary offerings include the Moe Nine fire-prevention joint (heat-expansion material blocks the pipe during fire, certified by MLIT and the Fire Safety Center), the Vinyl Core resin-based single-pipe system co-developed with Maezawa Kasei Industry in 2016, the Manku Kit air-pressure leak testing system co-developed with Tetsuken Construction, drainage fixtures and manholes, and renovation/maintenance services via the JUST Method that replaces pipes without breaking floor slabs.

The company monetizes primarily through B2B hardware sales of drainage system components, with a secondary services stream from renovation and maintenance projects. Go-to-market is enterprise field sales targeting apartment developers, general contractors, equipment installation companies, and public-sector housing bodies (UR City Development Organization, formerly Housing and Urban Development Corporation), executed through pipe-material trading distributors and direct sales teams based at the Nagoya headquarters and the Tokyo Metropolitan Core Center (MCC); a direct online channel, haisui.com, was launched in 2010 to complement the distributor network. Pricing is quote-based with a publicly downloadable catalog, and the company executed price revisions across multiple product lines in May-June 2026 amid Middle East-related supply chain pressures disclosed in April 2026.

Operationally, Kojima operates a 51-100 person organization with three Japanese sites: the Nagoya headquarters (which includes a 9-story experiment tower used for drainage performance testing since 1977), the Tokyo MCC sales office, and the Kuwana Kojima Logistics Center. The company holds ISO 9001 certification (since 1998), maintains 86 patents as of 2022, and has received 14 consecutive years of invention encouragement awards from Chubu regional and Aichi Prefecture bodies. It is family-owned, currently led by President Kojima Hisanori with Chairman Kojima Seizo, and counts Nagoya Small and Medium Enterprise Investment Co. as a major shareholder following a 1982 capital increase to 45 million yen.

Name

Kojima Seisakusho

Legal name

株式会社小島製作所

Website

https://kojima-core.co.jp

Company type

Private

Founded year

1919

Operating status

Operating

Headcount range

51–100 employees

Short description

Kojima Seisakusho is a privately held Nagoya-based Japanese manufacturer founded in 1919 that designs, produces, and sells building drainage equipment and system joints—including single-pipe drainage, fire-prevention joints, and resin-based systems—for developers, general contractors, and public-sector housing bodies in Japan.

Ownership category

akta.pro rank

Product category

Building Drainage Equipment

akta.pro primary industry

Plumbing & Building Drain/Waste/Vent (DWV) Pipe & Fittings (IMANADAG)

akta.pro secondary industry

Drainage, Waste & Vent (DWV) Systems & Components (IMADALAE)

Keywords

• Building drainage equipment
• Single-pipe drainage systems
• Fire prevention joints
• Drainage pipe renovation
• Leak testing equipment

Headquarters

HQ city

Nakagawa

HQ country

Japan

HQ region

Asia

Offices3 records

Markets served

GTM type

B2B

Offering type

Hardware or Manufacturing

Cost components

Supply Chain, Personnel, Technology or R&D, Marketing or Sales, Operations, Infrastructure

Revenue model

1. Building Drainage Equipment Manufacturing and Sales: Design, development, manufacturing, and sales of architectural building drainage equipment and system joints including single-pipe drainage systems, fire prevention joints, manholes, and drainage fixtures.
2. Maintenance and Renovation Services: Drainage pipe update, renovation, and maintenance services providing new product proposals and construction methods.

Go-to-market motion1 record

Distribution channels3 records

Marketing channels4 records

Core offering

Kojima Seisakusho designs, manufactures, and sells building drainage equipment and system joints under its own brands CORE, Moe Nine, Vinyl Core, and Manku Kit, including single-pipe drainage systems, fire-prevention joint fittings, drainage fixtures and manholes, and air-pressure leak inspection kits. The company also provides drainage pipe renewal, renovation, and maintenance services for existing buildings. Its products serve apartments, hotels, nursing facilities, schools, hospitals, and public buildings in Japan, with named installations including Tokyo Skytree.

Product overview

Kojima Seisakusho is a manufacturer specializing in building equipment drainage equipment and system joints. The company offers a comprehensive portfolio of drainage solutions including the CORE single-pipe drainage system as its core product, the fire-resistant Moe-Nine joint system, traditional drainage fixtures and manhole products, the Vinyl Core resin drainage system (resulting from alliance with Maezawa Kasei Kogyo), the Manku Kit for leak testing using air pressure technology, and drainage pipe renewal/reform/maintenance services. The products serve various building types from low-rise to ultra-high-rise residential, commercial, and public facilities, with applications including Tokyo Skytree.

Differentiator

Problem solved

Functional benefit

Brands

• CORE: 단관식 배수 시스템으로, 아파트와 호텔 등에 사용되는 주요 제품군
• ビニコア
• モエナイン
• 満空キット
• JUST工法

Products and services

• CORE Single-Pipe Drainage System (単管式排水システム CORE) Single-pipe drainage system with superior durability, workability, and drainage capacity that supports comfortable drainage environments in buildings. Achieved high market share in Japan's single-pipe drainage system industry. Serves developers, general contractors, and equipment construction companies specifying drainage for mid- to high-rise residential buildings.
• Moe Nine Fire-Prevention Joint System (延焼防止材付継手 モエナイン) Fire-resistant joint system where fire-resistant (heat-expansion) material blocks the pipe during fires, preventing heat, flames, and smoke from spreading to upper floors. Holds Ministry of Land, Infrastructure, Transport and Tourism certification and Fire Safety Center evaluation. Targets high-rise residential, hotel, nursing care, school, and hospital buildings where fire compartmentalization is critical.
• Drainage Fixtures and Manholes (排水金具・マンホール) Building equipment drainage fixtures and manhole covers that suppress water clogs and odors, maintaining sanitary drainage system environments and comfortable living. Targets developers, contractors, and public-sector building projects.
• Vinyl Core Resin Drainage System (ビニコア) Resin version of Kojima's single-pipe drainage system, offering powerful and silent performance, with superior drainage performance, sound insulation, workability, impact resistance, and corrosion resistance. Suitable for a wide range from mid-rise to ultra-high-rise residential buildings. Developed in alliance with Maezawa Kasei Kogyo.
• Manku Kit Air-Pressure Leak Test Kit (満空キット) Drainage system leak inspection kit that uses air pressure instead of water for testing, addressing problems with traditional water-filled (満水) testing methods. Environmentally friendly approach developed with Tetsuken Construction (鉄建建設). Targets contractors and maintenance teams performing drainage system validation in new and renovated buildings.
• Drainage Pipe Renewal, Reform and Maintenance Services (排水管更新・リフォーム・メンテナンス) Drainage pipe renewal, renovation, and maintenance services for existing residential and public-housing buildings, offering innovative products and methods — including the patented JUST Method — as a drainage equipment manufacturer focused on comfortable living environments. Targets renovation contractors and housing management bodies updating aging drainage systems with minimal occupant disruption.

Quantifiable outcome

• 40% improvement in drainage performance with CORE joint 80A series
• +2 more outcomes

Named customers6 records

Segments4 records

Ideal customer profiles3 records

Technology focussed No

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature5 records

Partnerships

Four partnerships are on record, tiered core and major.

• Maezawa化成工業 (Maezawa Kasei Industry)coreStrategic or Co-development Partner · 29 February 2016Strategic alliance forVinyl Core (ビニコア) resin-based drainage system. Combined Kojima's drainage system expertise with Maezawa's resin molding capabilities. Product offers superior drainage performance, sound insulation, workability, impact resistance, and corrosion resistance.
• シーシーアイ (CCI)coreStrategic or Co-development Partner · 15 October 2010Collaboration with soundproof drainage pipe manufacturer CCI to develop Moe Nine (モエナイン) fire prevention drainage system. Heat-expansion material expands during fire to block pipes, preventing fire spread.
• 鉄建建設 (Tetsuken Construction)majorStrategic or Co-development Partner · 1 January 2007Joint development of full-empty test jig (満空試験治具) for air pressure-based leak testing. Also collaborated on JUST method for drainage pipe renovation without breaking floor slabs.
• 長谷川鑄工所 (Hasegawa Casting)majorStrategic or Co-development Partner · 1 April 2005Production efficiency partnership for drainage equipment and manhole casting. Later expanded to stainless steel drainage equipment under P-trap COM brand in 2008.

Scale indicators4 records

Recent moves9 records

Expansion highlights5 records

Broad incumbents

• LIXIL Group: Major Japanese building products conglomerate with broad portfolio including plumbing fixtures, drainage systems, and bathroom/kitchen products. Targets similar developers and contractors but with much greater scale and product breadth than Kojima's niche focus.
• Cleanup Corporation: Japanese kitchen and bathroom fixtures manufacturer serving similar residential and commercial construction customers in Japan, with overlapping building equipment focus though broader product scope.
• Sekisui Chemical Co., Ltd. Major Japanese chemical and building products company with significant pipe and plumbing product lines, serving similar infrastructure and construction markets. Operates at substantially larger scale with diversified product portfolio beyond drainage.
• TOTO Ltd. Japan's largest plumbing fixtures manufacturer with broad product portfolio spanning toilets, washbasins, and drainage-related fittings. Operates at much larger scale than Kojima but serves overlapping developer and general contractor customers in Japanese building projects.
• Kubota Corporation: Japanese industrial conglomerate with pipe, valves, and infrastructure product lines serving water and drainage applications, including ductile iron pipes for building and municipal use. Much larger and more diversified than Kojima.
• Rinnai Corporation: Japanese water heating and building equipment company serving similar construction and B2B customer base, with overlapping building equipment focus but a much broader product portfolio and global presence.
• Panasonic Corporation: Japanese electronics and building products conglomerate with housing equipment including plumbing, water heating, and bathroom products serving similar B2B construction customers in Japan, though at much larger scale and broader scope.

Regional players

• Geberit AG: Swiss-based global leader in building drainage systems (single-pipe drainage, installation systems, plumbing technology) with direct product overlap to Kojima's CORE offering, but primarily serves European and global markets rather than Japan.

Direct peers

• Nihon Hume Corporation: Japanese manufacturer of concrete pipes and drainage infrastructure products (hume pipes), serving similar municipal and building drainage applications. Comparable niche focus on drainage systems though different material base than Kojima.
• Maezawa Kasei Industries: Strategic co-development partner on Vinyl Core resin drainage system. Japanese manufacturer with overlapping focus on drainage pipes and resin-based building products, serving similar developers and contractors in Japan.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat4 records

Key risks7 records

Key highlights7 records

Customer concentration

Compliance3 records

Revenue estimate

Valuation estimate

Number of profiles

Profiles2 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Kojima Seisakusho