Troubleshooting My Philips Avent cup is leaking A Philips Avent cup may leak for more than one reason. Find out how to fix it yourself and avoid any leakage. Tips and tricks 1) Always ensure that the spout and valve are properly assembled. If you removed the valve for cleaning, please place the valve on the spout, ensuring it is on securely: Insert the spout assembly upwards inside the screw ring, until you hear a click. 2) Check that the ring has not been over-tightened as this can prevent the valve from operating correctly. 3) Sportster and Magic Cups are not suitable for hot, fizzy or pulpy liquids. 4) Do not use cups with spouts to mix infant formula as this may clog the non-spill valve and cause components to leak. If you have lost or damaged the spout or valve, replacements are available to purchase by clicking on our parts and accessories link, or by contacting Philips Customer Care.