Vacuum sealed

[Texas_T]

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.

Thanks.

[Wolverine]

What year and model is your unit ?

[chipper]

Originally Posted by Wolverine

What year and model is your unit ?

Found it in one of his past post.

2011 31.5FBHS Eagle Super light

[Texas_T]

Chipper, that is correct

[RVhiker]

I've had a vacuum develop in the small section of piping between the valves and the outlet when you've descended from a mountainous area down to the flats; it's simply the air pressure is lower at high altitudes. If the valves and the cap are sealed well, the lower pressure in that area is seen when you open the cap.

Also, if you close the cap and valves when it is very hot and open the cap when it is quite a bit cooler the air pressure in that area will now be lower as it has cooled off. Opening the cap would again cause this lower pressure to be seen.