1. Step: Repair of dry and leaking cracks in the concrete substrate with KÖSTER KB-Pur 2 IN 1. 2. Step: Restoration and relevelling of the concrete substrate with KÖSTER Repair Mortar Plus and KÖSTER Betomor Multi A. 3 Step: Waterproofing the basin with KÖSTER NB 1 Grey and KÖSTER NB Elastic Grey (for areas in danger of cracking).