I run three basic Youngs PBs, each with the basic non-injection type cap. Apart from the tap, there are normally only three source of leaks on these, the cap to PB seal, the relief device seal, and the seam on the PB itself. I have had leaks of all three types but the first two are usually easily sorted (I keep spare cap seals which helps), though if the PB seam splits out of warranty it's a chuck away job (Youngs replaced mine). Any leak is usually found with the help of soapy water. I have also had a pin hole leak on the shell of a PB, but it was well over 40 years old and a freebie!