Yeah . . . much more expensive if you have well water . . . typically you need to buy a couple of pressurized tanks which quickly adds up vs. doing the system off city water. Ah . . . the old fire grenades. Is this one empty or is it filled with salt water? Typically I see these with a red or green filled liquid which is typically carbon tetracholride -- which can be quite nasty to the nervous system -- not to mention that it can convert to phosgene gas when it comes in contact with high heat.