In Rača at Zlaté Krídlo apartments, Pureco SK installed a retention tank with the capacity of 140 m3 in August 2017. The Investor was Sakmont s.r.o. and the total amount of the project was 31 000 EUR. The specialty of the solution is the size of the hole (800 x 1 500) because it was the first time we used concrete tanks with such as huge assembly holes. The seal was used between the concrete tanks (SikaSwell S-2 in the contact area and Stachema Reparal DUR E F from inside). Another advantage: there is no need for more than one manhole in all volumes of retention tanks.