Additive delivery systems and containers

An additive delivery system comprising:

• a base liquid container having an inner volume to hold a base liquid, a bottom and a threaded mouth;
• an additive reservoir including at least one wall defining a space holding a liquid additive and an outlet from which the liquid additive exits the additive reservoir;
• a cap assembly configured to threadedly engage with the threaded mouth, the cap assembly having a bottom, a top, a spout at the top of the cap assembly and configured for movement between open and closed positions to control flow of liquid from the spout, at least one wall that defines an additive reservoir cavity to receive the additive reservoir, and a metering port configured to receive the liquid additive from the outlet of the additive reservoir;
• and
• a base liquid flowpath extending through the cap assembly to the spout, the base liquid flowpath fluidly coupled to receive the liquid additive from the metering port at a mixing area to mix the liquid additive with the base liquid, and including a delivery tube that extends from a lower end positioned near the bottom of the base liquid container to an upper end engaged with the cap assembly, and a one-way valve in the base liquid flowpath upstream of the mixing area that prevents backflow of the base liquid into the base liquid container.