Maintenance Services For Water Purification Installations (Maintenance Of Drinking Fountains "Pf-1-4K" With A Filter For Cleaning And Disinfection Of Drinking Water In The Specialized School Of I-Iii Degrees No. 307 With In-Depth Study Of Natural Sciences, Desnyan District, Kyiv, At The Address: Str. Liskivska, 4B, According To The Code Of The Classifier Dk 021:2015 (Срv): 65120000-0 (Operation Of Water Treatment Plants)