Kitchen & Bathroom Tap Cartridge's

Hello I have just purchased a Bailey Pageant Monarch 7, and unfortunately found that when the Power and Water Pump is turned on the Kitchen & Bathroom taps both leak water from the base of the taps. I have looked online and people have suggested that it maybe just the cartridge inside the taps might need replacing, does anybody know what size of cartridge to order 35mm or 45mm my caravan is stored a little bit away from my property, just trying to save myself a trip 👍