In order to increase the spatial resolution of tropospheric delays derived from GPS observations, existing GPS networks assembled from dual frequency (DF) receivers must be densified. For economic reasons, low-cost single-frequency (SF) receivers are considered for the densification. The Satellite-specific Epoch-differenced Ionospheric Delay model (SEID) was developed at the German Research Centre for Geosciences (GFZ) to derive the ionospheric corrections for SF GPS receivers. Those corrections allow synthesizing a L2 observable for SF receivers, and existing GPS processing packages can analyze the resulting observables (L1 and synthesized L2) using the same methodology as with DF receivers. The SEID model has already been successfully applied to tropospheric Zenith Total Delay (ZTD) and station coordinates estimation. To assess the possibility of densifying an existing GPS network with low-cost SF GPS receivers, observations from 258 German DF GPS stations are treated as observations from SF GPS stations (only L1 GPS observations are used). While in a previous study ZTD products were validated, in this study Slant Total Delay (STD) and Slant Water Vapor (SWV) products, derived from SF data and the SEID model, are validated using tropospheric products derived from DF data, a Water Vapor Radiometer (WVR) and a numerical weather model.