There are tabs on the inside of the hose adaptor fittings. They are positioned in the centre of the top on the unit. Please ensure you are fully opening and closing the taps using the lever. Overtime, with incorrect use these tabs may weaken if not fully opened and closed during use. Ensure to hold down the tap adaptor when lifting the lever for a safe removal. 

Each time you maintain your unit, remember to lubricate the o-rings before putting the unit back together. 
Accidental damage on parts such as these are not covered under the manufactures warranty. You can find spare parts for your External Filter listed here

Important: Disconnect mains electricity supply before handling or attempting maintenance. Always fully read and check the troubleshooting section within your product instruction manual.