Collection:Filler And Breather Plugs

Filler and breather plugs close the filling opening of hydraulic tanks and gearboxes and let the tank breathe. As the oil level rises and falls during operation, air must flow in and out of the tank; without a breather, the tank builds up pressure or vacuum, which strains seals and disturbs the pump suction.

Several versions are common. A plug with air filter stops dust and dirt from entering the tank with the incoming air, which keeps the oil clean and protects pumps and valves. A plug without filter only closes and vents the opening. Versions with a dipstick let you check the oil level at the filler opening, with or without an air filter.

To select a plug, first match the thread type and size to the tank port: cylindrical BSPP (G) and metric threads are not interchangeable. Choose a filtered version wherever the surrounding air carries dust. Add a dipstick when the tank has no other level indication. Plastic plugs are light and corrosion-free; metal plugs suit environments where the plug may be knocked or exposed to heat.