https://www.jbl.de/it/blog/detail/754/water-backflow-stop-prosilent-safe-for-diaphragm-pumps?country=ch
Water backflow stop (ProSilent Safe) for diaphragm pumps
To prevent the aquarium from leaking, the air hose conveying air into the aquarium from the air pump needs to have a check valve.
for diaphragm pumpswaterbackflowstopsafe