2017 wildwood clean water tank loosing water

[mkosu04]

Originally Posted by rockfordroo

Provided it's FULL. If it's not full, you could have an issue.

not really, due to my point #1 - the shape of the tank will allow for adequate expansion
(providing you are not loading it in a jet and flying to your destination)

Originally Posted by kzoromski

Attachment 141246

Actually that connection has a check valve inside. You can see if if you remove the screen.
So it will not allow pressure to escape.
(I know this for sure, because when I bleach my lines in the spring I will remove that screen and depress the check valve with my finger to flush water into this line)

I presume you have some sort of valve that allows you to fill your water tank from the main water connection?
Most (some?) campers have a separate port for filling the fresh water tank that is most likely less air-tight. The cap is a quarter-turn and it will likely vent pressure slowly.

[rockfordroo]

Originally Posted by mkosu04

not really, due to my point #1 - the shape of the tank will allow for adequate expansion
(providing you are not loading it in a jet and flying to your destination)

Sorry - When the air in the tank expands, its force will be felt on every square inch of wall of the tank. The tank will expand however much it needs to in order to hold in the pressure. The largest surfaces (typically top and bottom) will expand the most. It doesn't matter if it's water pressure or air pressure. Pressure is pressure. As previously discussed, a pressure difference of 5 psi (going from sea level to 11,000 ft) over a 2 x 6 ft tank top will exert 8,600 pounds of force. That WILL bow out the tank!

[kzoromski]

That's the only fill line I have. Can't speak for any other 17' wildwood. Only other connection I have is city water connection.

[kzoromski]

Didn't really pay it much attention till I went to add water on on first trip last year . Then I said what the #*#}* where can I put a jug of water in?

[kzoromski]

[kzoromski]

Maybe something like this then. If it does get pressure it will release but would still hold the water in on the way to your destination

[kzoromski]

It would need to be open once at site though. Scratch that I guess

[mkosu04]

Originally Posted by rockfordroo

Sorry - When the air in the tank expands, its force will be felt on every square inch of wall of the tank. The tank will expand however much it needs to in order to hold in the pressure. The largest surfaces (typically top and bottom) will expand the most. It doesn't matter if it's water pressure or air pressure. Pressure is pressure. As previously discussed, a pressure difference of 5 psi (going from sea level to 11,000 ft) over a 2 x 6 ft tank top will exert 8,600 pounds of force. That WILL bow out the tank!

your math skills may be good, but your engineering skills are poor.

Yes, 5 PSI on a 2 foot by 6 foot wall will create a distributed force of 8,640 pounds across the entire surface. But this assumes a completely rigid container that does not allow the contained volume to change.

My point is that the very large flat surface will deflect, thereby changing the volume inside the container and equalizing the pressure. Even if you have a 5 PSI change in atmospheric pressure (and the tank fittings are all 100% airtight) the pressure or vacuum inside the tank will never be 5 PSI.

And, at the end of the day, you still have only 5 pounds of force on any single square inch of the surface. (if you don't equalize the pressure by changing the volume inside the container)
Most plastics have a tensile strength in the thousands of pounds per square inch (4-6 KSI for PP) so I'm guessing that the container could withstand a 5 PSI internal pressure. But I'm not sure what material they use or what thickness... and in reality you will probably fail at a corner or at a knit line in the tank before you reach the base material tensile strength.

[rockfordroo]

Originally Posted by mkosu04

your math skills may be good, but your engineering skills are poor. Right back at cha.

Yes, 5 PSI on a 2 foot by 6 foot wall will create a distributed force of 8,640 pounds across the entire surface. But this assumes a completely rigid container that does not allow the contained volume to change. The amount the tank would expand before it fails most likely won't drop the pressure much, depending on the actual void space.

My point is that the very large flat surface will deflect, thereby changing the volume inside the container and equalizing the pressure. Even if you have a 5 PSI change in atmospheric pressure (and the tank fittings are all 100% airtight) the pressure or vacuum inside the tank will never be 5 PSI. If you start with 14.7 psi inside and outside the tank, then drop the outside pressure to 9.7 psi by going to 11,000 ft, you'll have 5 psi across the tank. See above for comment on tank expansion.

And, at the end of the day, you still have only 5 pounds of force on any single square inch of the surface. (if you don't equalize the pressure by changing the volume inside the container)

Most plastics have a tensile strength in the thousands of pounds per square inch (4-6 KSI for PP) so I'm guessing that the container could withstand a 5 PSI internal pressure. But I'm not sure what material they use or what thickness... and in reality you will probably fail at a corner or at a knit line in the tank before you reach the base material tensile strength. I never said where it would fail, but I agree, it will be some kind of seam. You're also right that 5psi won't fail it, but even if it doesn't fail, balloning of the tank on many of these units will fail the supports and the tank will drop out.

My comments in red.

[Murbella7]

This is a bit old but I'll add my bit anyway. My fresh tank apparently had a split in it from day one. I could fill it and yet after about an hour driving it would be near half empty. It was only when it eventually split completely and gushed water everywhere did we discover this. It had to be replaced. The cause was a badly made support system that allowed the tank to 'float' around, wearing through the poly material.