Hi Ian. You're welcome, and £iver on its way. The EV itself won't leak water - at least not any significant amount. If the diaphragm inside it ruptures, you will possibly get air going into your system, but this will be expelled if your boiler has an auto-air vent. But this will cause the pressure swings. First thing is to test the EV by pressing the shraeder valve and also taking a pressure reading from it.