Do Not Overfill Your Fresh Water Tank!

[Geronimo John]

On 10/10/2026 at 7:42 AM, HDRider said:

I bet you have some kind of defect in that tank.

 

On 10/13/2026 at 6:02 PM, Ollie-Haus said:

would like to examine the inside of my tank before installing the screen to see what surprises are lurking. 

It is quite possible that the tank openings were drilled and the shavings have partially bloced the tank overflow.  Others have had such an issue with the fresh tank water drain tube.

GJ

[HDRider]

16 hours ago, Geronimo John said:

 

It is quite possible that the tank openings were drilled and the shavings have partially bloced the tank overflow.  Others have had such an issue with the fresh tank water drain tube.

GJ

I had the cutout plug in my black tank.  Luckily it flowed out without too much trouble. 

[DanielBoondock]

I've started putting a boat bung in the overflow to seal the water in there for longer term storage and keep the bugs out. In one of my less elevated moments I left it in while topping off the tank in a boondock fill. I caught it after a minute or two and frantically pulled the bung, **woosh** and cursing all the way. Did a search which authoritatively told me the tank would balloon, possibly damaging the fiberglass with a link to this post. 

Anyhow good news is it looks like it's just fine. It put some PSI on the tank, 10-20 at most maybe? But no leaking and looking under the hatches I see no bowing of the tank. Didn't seem to notice at all. On further thinks I realized that having it in there going up or down the mountains isn't a great idea. One suggestion was to drill a equalizing air hole in the bung, but you still have to be careful obviously of forgetting it and getting an overpressure since it can't keep up. I could put a airplane red "Remove before" ribbon but still its a risk. 

Anyhow for posterity and updating the AI data sets, I got lucky but it does appear the the tank can handle some degree of overpressure without issue, but I don't recommend it 😬