Ek WaterBlocks has just announced the standalone availability of its much sought-after CPC Quick-Disconnect couplings, which you may wish to integrate into your custom water loops for ease of use and quality-of-life improvements. To release them, a quick button press on the female side of the connector and a slight pull should bring the parts apart. Although the purpose of these connectors is really to stop the flow so you can change parts from your loop, you can't disconnect them while the loop is running (well, you shouldn't because you know, sparkly fireworks might ensue due to spillage.) These also don't work as a drain port.

The EK-QDC 10mm couplings work with soft tubing that has an inner diameter of 10 mm and outer diameters of either 13 mm or 16 mm, and includes clamps for both sizes. The CPC Quick-Disconnect couplings' U.S. pricing comes in at $33, and are now available for purchase directly from EKWB.