Anybody tell me what size pipe I need to do a leak off test. Is it 3mm i.d?

2003 KJ Liberty 2.5 CRD

to make a home made tool you need a pvc soft clear hose inner id 1/8 outside id 1/4 4 hoses 3ft long . remove return hose assembly put it in hot water to make it softer , easier to remove plastic t connectors , don't brake them . hook up clear hoses cap other side of t connectors install each t connects onto injectors secure with clips , get 4 small glass cups tape them drill holes through there lids push hoses in run engine 2 min at idle check fuel level ,must be almost same