Density. All models reproduced the experimental density of water reasonably well, with no model published after 2006 presenting a difference from experimental value above 0.7%. This is perhaps unsurprising, as density is one of the properties almost every water model is parametrized to reproduce. Models published before 2000 tended to reproduce the experimental density value more poorly in this study, at least in part due to the use of the particle-particle particle-mesh (PPPM) 126 treatment of longrange electrostatics used here. While PPPM and the related particle-mesh Ewald (PME) 127 are commonly used in simulations today, many of the older water models were developed with a relatively short non-bond cutoff and no treatment of long-range electrostatics. The TIP3P-Ew, TIP4P-Ew, and TIP5P-Ew models, published in 2004, represent reparameterizations of the original TIP3P, TIP4P, and TIP5P models, respectively, for use with Ewald summation for long-range electrostatics. All three Ewald models improved the reproduction of experimental density without changing the water model geometry, with the TIP3P-Ew and TIP4P-Ew models changing both charge and Lennard-Jones parameters, and the TIP5P-Ew changing only the Lennard-Jones parameters. The COMPASS water model exhibited the greatest deviation from the experimental density in this study, but like the TIPfamily models this is most likely due to the PPPM treatment of long-range electrostatics. Indeed, a 2004 paper found the density error to be 0.34% when a group-based cutoff scheme was used, and 3.25% when an Ewald summation was used. Overall, these results suggest caution when combining older water models with current long-range electrostatic treatments like PPPM and PME if accurate reproduction of water density is desirable.