Howdy, I have a question about the sewage system every time I go to drain my tanks as soon as I go to remove the cap to hook up the hose I break a vacuum. Is this common ? and even though the gates are still closed I get some leakage past one of the gates, the leakage I understand, I just have a gate that is not sealing all the way but the vacuum break has got me curious. This has been happening sense day one. Anybody have a suggestion or ideal why this happens.