Water Treatment Services - For 40 years, National Water Service has been installing and servicing complex water systems in Homes, Restaurants, Hotels, Hospitals, Shopping Centers & more all over the DC, Baltimore & Frederick Metro areas. Whether on City Water or a Well System, water quality can vary quite a bit from street to street and we are happy to do a basic analysis of your water and/or existing water treatment at no charge. Our installers are all professionally trained in Water Treatment, Water Testing Services, Purification, Well Pumps, Water Heater Services, Filtration and are certified well water specialists!