How do I test or research any damage done to my FW holding tank

[Best Papa]

After purchasing a used 303RLS we wanted to take it out into the desert to try it out dry camping as all of the campgrounds were closed. I followed the guide panel on how to fill that holding tank for dry camping with an attached FW hose. After a bit we noticed the floor starting to bulge and heart a "pop" or something similar. I shut of the fill and noticed that underneath there was also a bulge in the tank. I opened the bottom release valve and with obvious pressure the water poured out and the floor returned to normal. After empty I closed the valve and then noticed on what I believe was the blue overflow tube was capped with a 1/2" pvc cap. I was able to remove it with a simple twist but now am afraid there may have been damage done.

I did take the unit out using city water only and everything worked fine although I did seem to fill the galley holding tank in just a day which to me was awfully fast so don't know if that could be connected somehow.

So how do I check to see what damage was done? It's all sealed below.

[boyscout]

After purchasing a used 303RLS we wanted to take it out into the desert to try it out dry camping as all of the campgrounds were closed. I followed the guide panel on how to fill that holding tank for dry camping with an attached FW hose. After a bit we noticed the floor starting to bulge and heart a "pop" or something similar. I shut of the fill and noticed that underneath there was also a bulge in the tank. I opened the bottom release valve and with obvious pressure the water poured out and the floor returned to normal. After empty I closed the valve and then noticed on what I believe was the blue overflow tube was capped with a 1/2" pvc cap. I was able to remove it with a simple twist but now am afraid there may have been damage done. I did take the unit out using city water only and everything worked fine although I did seem to fill the galley holding tank in just a day which to me was awfully fast so don't know if that could be connected somehow. So how do I check to see what damage was done? It's all sealed below.

That's unfortunate. The cap on the overflow was likely added by the previous owner - sounds like you already know that the tank should have overflowed from there when it was full. That outlet should ONLY be capped while moving to a campsite with a full tank and should be uncapped at all other times, as you've discovered. There are people who think it should never be capped - it can be a problem if your journey involves significant changes in elevation - and in many cases there's no need for it. I bought a valve for mine after reading about the siphoning problem that some trailers have, but after a number of trips without closing it and without losing significant water supply I don't ever close it.

From your description my *guess* would be that the noise you heard was the tank popping something out of place - like a floor panel or cross-member - rather than the tank rupturing itself. The latter would almost certainly have released water onto the chloroplast and you'd see it sagging and/or water dribbling out one of the edges.

In your shoes I'd release part of one edge of the chloroplast to examine beneath the fresh tank. I don't know for sure where your tank is, but many of them are located over or just behind the rear axle. I'd be trying to ensure that the structure under the tank isn't damaged. A cell phone video camera on a stick might be useful. Then I'd fill it with water again and check it again - don't want the tank to fall out going down the road. With that worry removed I'd go for a drive with a passenger, both of you watching the sides of the trailer for water leaking. Seeing none, I'd return and check out the interior, make sure nothing is interfering with slides moving, that the floor isn't pushed up and that it seems solid under bouncing feet. Then I'd have a drink, anything but water.

Good luck.

[Richter]

I bought a valve for mine after reading about the siphoning problem that some trailers have, but after a number of trips without closing it and without losing significant water supply I don't ever close it.

I’ve read this as well, and struggle to understand the concept. In my opinion, the “overflow pipe” would be connected to the top, or near the top, of the tank, so that as the tank approaches full, there is an outlet for the water to escape if it is filled to a level higher than that point. The overflow pipe would not extend inside the tank. Understanding the concept of siphoning, the intake to the siphon hose has to be below the level of the water surface, not above it. Water cannot siphon if there isn’t an entry point below the surface.

In my opinion, since these tanks are somewhat shallow and wide, it is more likely that the water is sloshing from side to side, and going out of the overflow. I’ve never encountered that problem, but I tend to drive like the old man that I am, staying below 65 and taking corners slower. Maybe that’s the key to the “siphoning” issue.

As a side-note, I would never put a cap or valve on my overflow (I’d be concerned about forgetting it at some point, as in a “senior-moment” and face the same problem that was experienced by the original poster). I did, however, cut a 3” square piece of fiberglass screen and put it over the outlet, securing it with a zip-tie, to keep anything from crawling up into my fresh-water tank. Probably over-cautious, but that’s how I often approach life.

[powerscol]

@boyscout is correct - just unscrew the edges of the chloroplast . Its easy to do and fairly easy to get back up (use a board and a jack to lift as you pull and screw back in. I suspect you may have busted the retaining straps.

Question - you mention the blue pipe with the screw in cap. Are you sure that is not a low point drain. From the factory the low point drains protrude the chloroplast (one red and one blue 1/2" I believe) they will be side by side and both come from the factory with screw in caps. The fresh water tank vent line is also blue (3/4 inch) and is separate from the others. Just double checking. Pictures would help greately of the lines and what you find when you drop the belly.

Good luck

[Canyonlight]

Seems to be a new thread rehashing much of what was already covered in this thread from a few weeks ago. @Best Papa - did you replace the valve referenced in the thread below ?

https://www.mygrandrv.com/forum/show...660#post287660

Dan

[Best Papa]

No, I hadn't replaced anything. This is a new post from a couple of weeks ago but I've had some time to look into it more and we actually had the chance to take out the unit and try it out. No issues but again we didn't use the FW holding tank but city water. I may try and pull off the chloroplast this weekend if it doesn't get too warm. (We are on the edge of summer here in the desert). In a way I"m hoping it's just a support that I hope I can get to.
BTW I've been unable to reach the previous owner but will keep trying.

[powerscol]

No, I hadn't replaced anything. This is a new post from a couple of weeks ago but I've had some time to look into it more and we actually had the chance to take out the unit and try it out. No issues but again we didn't use the FW holding tank but city water. I may try and pull off the chloroplast this weekend if it doesn't get too warm. (We are on the edge of summer here in the desert). In a way I"m hoping it's just a support that I hope I can get to.
BTW I've been unable to reach the previous owner but will keep trying.

Please take some pictures of the existing piping

[Best Papa]

I'll try if I get under it this weekend. As I mentioned, it's starting to get warm here, over 100, so may put it off for a while. Or until fall when it cools off. Thanks for all of your help in this and will post again when I get more under and pull it apart.