Venting your fresh water tank. Why?

[digitalbill]

I have seen a few threads that talk about a vent for the fresh water tank. I am a bit confused.. How come I need a vent for the tank?
If it is fresh water, there would not be any gas build up (like a toilet) so, what am I missing?

[Forrest747]

several reasons for the vent. its to help keep the pressure in the tank the same as the atmosphere. think about the water cooler bottles and how it has trapped air to keep teh water from running all over the office. water pumps pulling water in will have a heck of a time doing it if there is trapped air, in the tank. it also a way to know that your tank is full.

also as your filling your tank its a way to have the air that is being displaced go out instead of through your fill line.

[Dale M.]

Also non vented tank forms a vacuum inside as you try to draw out the water... Hard on pumps (pulling against a vacuum) and you get little water....

Vent does not have to be much, something (fitting) with as small as a 1/8 inch hole in top of tank will do....

Dale

[48Rob]

If you have an electric pump and you don't replace the water removed with air, the tank, if plastic will collapse and break, or as mentioned, put a terrible strain on your expensive pump.
If too much, it may burn up.

And for filling, a vent is needed to allow the air in the tank to be pushed out by the water replacing it.

It is really very easy to add a vent line to a tank.

Rob

[PcHistorian]

so, say a vent and a hose fitting on the tank top, that loops to point down and exit under the trailer? I don't want water overflow into an part of my trailer, but I worry about the spray of mud and such up to get in the tank or clog the hose opening?

[Shadow Catcher]

Not mentioned is change in altitude, this summer we will be at 10,000 feet over Tioga pass, Big difference from the 700 feet where we are now. If your gravity water fill is not air tight it should suffice. I have two water inlets one for hookup to a water faucet that bypasses the pump the other is a gravity fill that does include a 3/8" tygon tube vet with a screen to prevent bug ingress. I have a five gallon flexible water container that can be hooked to the water filters and sit on top of the tear and fill the water tank. There are a number of version of this at http://rvadenver.com/new_page_30.htm
note this one has a vent

[Dale M.]

Not mentioned is change in altitude, this summer we will be at 10,000 feet over Tioga pass, Big difference from the 700 feet where we are now.

Actually Tioga pass is only 9,945 ft....

Dale

[Forrest747]

Your right Dave its that last 55 feet that are the toughest and most dangerous

[PcHistorian]

thanks s-catcher, that (http://rvadenver.com/new_page_30.htm) is some cool stuff.

[Shadow Catcher]

Ya but the destination is at Saddle Bag lake which is, I just hope it is open. I was there one year when the lake did not break up till after July 4th.
It is amazing how many things go through the side of the trailer, Compass Rose now has ten on the drivers side.