[Bobcat]

True007 .... short answer ... Swagelok fittings aren`t compatible with Parker hose . Swagelok makes a high grade instrumentation type fitting and their hoses are also intended for that application . If I caught one of my customers using fittings that weren`t ours on our hose , they would get a letter from our legal department telling them that was a no no .
Have people done that and gotten away with it ? Yes , but for every one that has , there are a bunch that got bit doing that .

Wrench87 ... What type of lines are you using ? You mentioned a vacuum valve , could that be interrupting the flow sporadically ? Does it work without the vacuum valve ? You can test the lines with a home made pressure tester as bobcowan did very easily . Plugs for the fittings should be readily available and the water test works great . If your problem is on the suction side , then a pressure test is useless . Just replace the hose as the liner may be collapsing and that is hard to detect .
Did you try blowing out the lines ? Maybe there is some crud clogging them .

Good luck .

Bob