Simple question about water system.

[kaveman]

Real basic question. As the water is pumped out from fresh water tank to faucets, air has to fill the empty space in the tank. Where does this air come into the tank? The water fill and city hook up seem air tight, when their caps are on.

I tried googling about it but all articles talk about purging air out of the system.

Thank you!

[obgraham]

There is an overflow outlet on the top of most all fresh water tanks. You can verify this by watching water spill out on the ground if you try to fill the tank more than its capacity.
Air enters the tank through this outlet as you empty the tank.

[kaveman]

Got it. Thanks a lot.

[BBQ]

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if the tank is under the RV, wouldn't that suck dirty air in when you use the faucet when driving? (of if you parked next to the dump?)

[gregmchugh]

Originally Posted by BBQ

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if the tank is under the RV, wouldn't that suck dirty air in when you use the faucet when driving? (of if you parked next to the dump?)

Yes, but it is a very small opening and a very slow flow of air as you use the water. I have never heard anyone get concerned about it but many people don't drink the water from the tank if they are worried about the purity of the water there...