^ The 9-meter diving tank being carefully lowered into position through the roof of the diving school building

Article by Karim Adahchour, Gpi


Commissioned by Baars-CIPRO, Gpi supplied two stainless steel water tanks which each have a diameter of six metres. The stainless steel water tanks have been constructed in compliance with the WHVBZ, the Dutch hygiene and safety regulations for swimming pools and related facilities. The combination of high humidity, chlorine fumes and a high temperature in swimming pools makes corrosion of materials possible. In the past, it was assumed that any stainless steel would be resistant to this corrosion, but several incidents have made it clear that this is not the case.
For this reason, the water tanks are constructed in the stainless steel grade 1.4401 (ASTM 316/ 316L). It has very good corrosion resistance, which makes it a useful material within a wide range of areas. It has an improved resistance to pitting and crevice corrosion in environments containing chlorides.
The tanks have now been installed on the third storey of the diving school. Measuring 9 and 3.5 metres deep respectively, the two tanks are linked to each other by a 1.35 metre deep connecting tank.

Diving school
The town of Enkhuizen has witnessed a highly unusual edifice rising above the surroundings of its Krabbersplaat industrial estate. The new diving centre BC-Opleidingen is five storeys in height and contains several water tanks of varying sizes. This diving centre is soon to become the number one location for marine, commercial and rescue divers seeking to learn and hone their professional diving skills in the Netherlands. The first training courses are planned in the new building for 2019.

Satisfying outcome

Jeroen Baars, the owner of BCOpleidingen, the training institute, is enthusiastic, “We had our first dealings with Gpi in 2007, with our first 9 meter training tank. Gpi was quick to understand our specific needs and delivered to our satisfaction in that project, so it was an easy decision to contact them again for our new stainless steel water tanks.” Initial talks proceeded to the satisfaction of both sides.
One peculiarity of the assignment was that the tanks had to be integrated within the architectural setting. “That meant effective coordination between engineers at Gpi and Ooms (the lead contractor) so that a detailed design was in place to ensure that stainless steel tanks could be slotted into the concrete shell in a technically responsible manner. The level of cooperation and teamwork which is required for such an integrated operation is exactly the reason that we decided to award the order to Gpi,” explains Jeroen Baars.

Challenging welding

Since the edging around the stainless steel water tanks and the connecting tank needed to be secured, this was a challenging installation job, with a lot of welding carried out on-site. Both the interior and exterior surfaces of the diving tanks required welding. Safety was a very important factor due to the height of the installation. Gpi works exclusively with SSC qualified welders, who listen carefully to the wishes of the client and deliver the highest quality.


The tanks were initially transported from the production site at GrootAmmers by a pontoon and transferred onshore by means of a floating sheerleg. The water tanks were then moved to their final destination on a trailer.
At the time of publication, installation of the tanks was in full swing. Gpi is putting the finishing touches in place and completion of the project is now within touching distance. An official event is planned for 3 December when the 480m3 tank will be filled with water. The entire building was due to be completed at the end of 2018.

(Note: original time of publication was December 2018. The diving tower has since opened)

Time-lapse movie

The main contractor for the diving school project, Ooms bouw en Ontwikkeling, recorded the construction of the ultramodern diving school as a time-lapse movie. Watch the movie to see how the water tanks were installed on the third floor of the building: https://www.youtube.com/watch?v=aRhVb5UKV_Y&feature=youtu.be&t=38

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