HK40D - HAKKO Diaphragm Kit 40L Our rebuild diaphragm kits are simple to install. They include diaphragms to fix both sides. Note: If your diaphragms are blowing out frequently, you most likely have an excess back pressure problem in your design. Check that your air delivery tube is large diameter and no kinking is occurring. Check your air diffusers for clogging. Ceramic style air stones need cleaning with muriatic acid every 3 months typically. Check that the number of air diffusers is sufficient to handle the air output of your Hakko pump. Too few diffusers will create excess back pressure.