Read more: About us

About us

Kolk is a manufacturer and supplier of fittings such as valves, hydrants, check valves and accessories for water supply and sewage network. We are expert in supplying the (drinking) water market at home and abroad. In addition to the delivery of products, we also offer specialized project support. About our organisation Our modern company has a rich history. We have a flexible organization with short lines of communication and a complete focus on the customer needs. Flexibility, reliability, quality and durability are the core objectives of the organization. Our products and services Our range of products includes valves, hydrants, flange fittings and accessories. We have, based on years of knowledge and experience, specialized in the supply to the (drinking) water supply market. Our focus on this market is to act as a "one stop shop". We also offer professional project support to pipeline projects. Features of the product range of Kolk Our product range is characterized by: high-tech products, innovative solutions a wide range of products, a large stock, Inhouse production and coating facilities, Short delivery times, Flexible product adaption to customer demand. All our products meet all relevant national and international standards and product qualifications. Our customers On the Dutch market, we have been a reliable partner for a long time for the major water supply companies and their suppliers (contractors). Our products are delivered to international groups and contractors for the European and African markets.
Check our references.  More about Kolk We have a wide range of stock, so you can get qualified products in short time. Our qualified staff is at your service. Thanks to our many years of experience you can always count on expertise advise. Want to know more about Kolk? Please contact us or leave a callback request.
Read more: History


Appendagefabriek Kolk was founded in 1922 with support from the Dutch water supply companies. The aim was to ensure the supply of materials for the construction and the expansion of the drinking water network. Upto today Kolk is an independent family business where the fourth generation is active. With the knowledge and experience obtained by our rich history Kolk is able to develop products ever further and improve and modernize them.     Knowhow and experience are the basis for progress Kolk has evolved over the years from a traditional manufacturing company to a modern flexible organization. This development is centered around knowhow and experience.     Highlights from the history of Kolk Below is a summary of some highlights from the history of Kolk. 1923: The first hydrant The first Kolk hydrant was designed in 1923. Our hydrants are still a household name in the market. From 1923 until after World War II In the past Kolk has delivered many products to the former Dutch colonies such as Indonesia, Suriname and the Netherlands Antilles. The 60s: shipbuilding In the sixties the shipbuilding market, particularly tanker construction a was an important  user of the products. The 70s and 80s The construction of the Oosterschelde storm surge barrier in 1979 received parliamentary approval after which construction has started. Kolk has delivered all valves for the barrier. From past to present Technological developments have always influenced the history of Kolk. The developments in the drinking water supply market in recent years have initiated the following developments at Kolk: an extension of the product range, product innovation, short delivery times and modern distribution channels The products and manufacturing techniques are constantly adapted to the latest technology developments and the needs of the market. The organization now focuses on assembling, coating and testing of high-quality products and where the raw materials and components are sourced through a worldwide network of qualified suppliers. Do you want know more about Kolk? This page tells you more about the history of our company. Do you want to know what we can do for you and what value Kolk offers? Let us introduce ourselves further to you. Read more about the production, our quality policy, corporate social responsibility and our team. You can also contact us or leave a callback.
Read more: Team


At Kolk an enthusiastic, customer focused and professional team is awating for you. The team is characterized by craftsmanship, years of experience, good cooperation and stability. We daily translate the company goals like flexibility, reliability and quality in solid action. Learn more about the team Kolk? Let us introduce ourselves to you. Introducing ourselves We would like to introduce the team to you: Managing director Johan Kolk Operations manager Raymond van Stegeren Sales Mathilde Romme-Poelman Secretary and administration Rinske Kuper – Reuvers Financial control Anne-Marie Deterd Shop manager Michael Koning
Read more: Facilities


The facilities of Kolk provide for the full control of the production cycle in-house, from design to delivery and administration. Kolk’s factory is equipped with modern machinery. Delivery reliability and short lead times are core values in our policy. This translates into an efficient production process in all phases. Design and engineering The design department uses 3D CAD systems which are used for engineering of proprietary products and for customized solutions. The use of these systems leads to effective production, shows all the details and makes any problems are immediately clear. Production Our modern machine park is tailored to the needs of the market where quality, flexibility and production costs are important preconditions. The production and stock levels are set to short market delivery times. The production facilities consist of: Machining (CNC) Parts production Steel blasting and coating (GSK certificate) Assembly, hydro and functional festing and final quality control Packing and dispatch Important values in our organization are delivery reliability and short delivery times. Production capacity and production are fully geared to this goal. Coating of the products plays a crucial role in this. Kolk can by independently performing all coating operations guarantee the quality and turnaround time. Machining The facilities consist of: Turning (CNC) Milling (CNC) Drilling and tapping All machining operations are concluded with a final quality check. Parts production All components needed are manufactured both in house and sourced from qualified suppliers. The required raw materials consist largely of castings which we obtain worldwide from qualified foundries. After a thorough inspection and testing, we machine and coat these castings further in-house. Steel Blasting and powder Coating The (powder epoxy) coating facilities consist of a submersing robot for series production and two manual spray blocks for single pieces and large pieces. The process and process control certified by GSK (RAL-GZ 662). We apply coating with epoxy powder AKZO Resicoat (GSK certified).  Assembly, Hydro and functional testing and final quality control When Kolk we have assembly lines for serial and single piece assembly. There is a process control system implemented in order to ensure the quality and flexibility. All products are hydrostatically tested and functionally tested to the relevant standard requirements. Following testing, we carry a complete final inspection before the product is released for packaging and shipping.    
Read more: Quality


Quality is our first priority at Kolk. Our products meet the highest standards, but also reliability, delivery reliability and sustainability play an important role. In each work process we strive for a high customer satisfaction and a long-term partnership with our clients. ISO quality management system Kolk's goal is to fully meet the demands and expectations of the customer and where possible to exceed them. To facilitate this goal, there is a quality management system according to NEN-EN-ISO 9001: 2008. The ISO quality system is certified by KIWA. Product quality All products at Kolk are designed and manufactured in accordance with national and international standards and guidelines. Kolk products feature all the required certifications.  Mission and vision Kolk The mission of Kolk describes our core values and “raison d'être” of our identity. The vision explains what we want to achieve and where we are going. A clear formulation of our values and the future. Mission Kolk wants to be a flexible and reliable partner for all the companies involved in the water supply network and to keep a wide range of quality products in stock that will be acquired produced and distributed with a focus on sustainability. Kolk core values are: economically sound pricing policies appropriate range on stock product quality innovation delivery reliability thinking along and collaboration with its customers.  Corporate Social Responsibility (CSR) based on the principles of People, Planet and Profit / Prosperity as defined in the international standard ISO 26000 is the basis for our operational management in all its aspects. Vision A reliable, safe and economical (drinking) water supply is a primary need for humanity. Sustainable development with balanced and equal respect for people (People), the environment (Planet) and prosperity (Profit / Prosperity) is of great importance to ensure this water for present and future generations.

Corporate Social Responsibility (CSR)

Corporate sustainability is a precondition for the future of next generations. Caring for people, planet and profit fits in with the policy of Kolk. Our approach focuses on the continuity of the business, employment and the welfare of the staff and the service to our customers. Corporate social responsibility (CSR) is an integral part of our business and culture. CSR policy at Kolk Corporate Social Responsibility (CSR) based on the principles of People, Planet and Profit / Prosperity is defined in the international standard ISO 26000. This is the starting point for the business in all its aspects and Kolk has implemented this and put into action. CSR Performance Ladder Kolk has chosen the demonstrable implementation of its CSR policy through the introduction and certification of a management system based on CSR performance ladder. CSR values into practice Kolk has the defined the CSR core values which are of importance and relevant for the operation of the company and translated them into policies and various measures. This CSR core values are: Good governance and fair business Staff and Working Environment Social importance Stakeholders and stakeholder dialogue For details of our CSR values please refer to our CSR policy statement
Read more: Certificates


Quality management system ISO 9001:2015 Quality management system
Download certificate Product certificates Kiwa BRL-K602 Valves and other accessories for drinking water transport and distribution systems
Download certificate BRL-K614 Fire hydrants
Download certificate BRL-K772 Ductile iron pipes and fittings for the transport of drinking water
Download certificate BRL-K773 Ductile iron fittings for piping systems of PVC-U or PE (drinking water)
Download certificate BRL-K775 Ductile cast iron joints for pipes of nodular cast iron, steel, PVC-U or PE
Download certificate Powder epoxy coating GSK RAL-GZ 662Heavy Duty Corrosion Protection of Valves and Fittings with Powder Coating, Quality Assurance RAL-GZ 662/2 Special Quality and Test Regulations for Processes
Download certificate RAL-GZ 662/3 Special Quality and Test Regulations for Valves and Fittings with Powder Coating (Products)`
Download certificate