Disassemble, clean and disinfect all pump parts that come into contact with the breast and breast milk before you use the breast pump for the first time and after each use.
Be careful when you remove and clean the valve. If it gets damaged, your breast pump might not function properly. To clean the valve, gently rub it between your fingers in warm water with a small amount of dishwashing liquid. Do not insert objects into the valve, as this may cause damage.
You can also check your pump's assembly. Make sure that all the parts are securely connected and well-sealed. Loose or improperly installed parts will lower the suction level. Assembling the pump just after disinfection, when it is still moist, can improve the suction level.
If you own multiple different Philips Avent breast pump products, make sure you aren't mixing the parts, and do not use parts from other brands.
For more information on proper pump assembly, go to the philips.com/support page for your product and search "How to assemble" or check the online user manual.