I've received so much good advice here that I wanted to document and share my experience replacing the fresh water tank on my 2014 25' FB. I found little documentation on how to accomplish this and I'm hoping this post helps someone else facing a water leak.
Our leak started on I25 in Denver when traveling with a full tank of water on the way to dry camp in RMNP. Hey, Colorado, where old pavement meets new in a work zone the proper transition is a smooth patch, not a ditch! Anyway, I was losing about 3 or 4 gallons a day, slow enough to get home without emergency repair, but not slow enough to ignore.
I knew that the fresh tank was in the black plastic box between the axles, I did not know much more. That tank box also contains the low point drains on my trailer. That was easy to see, but the implications of that placement did not become clear until well into the removal process.
1. Preparation and inspection:
I first raised the trailer by pulling both sets of wheels onto three layers of 2x lumber. I used two 2x12s with a 2x8 on top. My tank was totally drained from the leak. Naturally, opening the drain petcock or pumping the tank dry would accomplish the same. Regardless of the method, the tank should be empty before proceeding.
Based on my experience, the proper process of diagnosis and, if necessary, removal begins above the tank. On the 25FB the tank connections enter the trailer in the space under the fridge which is on the street side. Remove the door to the storage space below the fridge and remove the kick panel that separates the storage space from the mechanical space behind it.
IMPORTANT NOTE: There was no fiberglass insulation visible in that compartment, but I knew after working in there for a while that there was lots of loose fiberglass present. That space should be vacuumed to remove contaminants and you should wear protective gear (long sleeves, gloves, particulate mask) when working in that space. From now on, I'll do the same in any mechanical compartments in the trailer.
An inspection on my tank was inconclusive, so I did have to remove it to learn more, but your issue may be diagnosable, and even repairable from above. Here's what you will be able to see when you get your head into the compartment:
1. Inside the black box that is fully visible below the trailer is a translucent white plastic tank.
2. From the top of the tank down are the following connections:
a. The vent which is a clear plastic 1/2" tube attached to a barbed elbow screwed into a flange on the top of the tank. This tube terminates at the small screen behind the water fill door on the street side of the trailer.
b. The fill line which is a large, ribbed tube that is clamped to an elbow which is screwed into a flange near the top of the street side end of the tank.
c. The drain line leading to the drain petcock on the outside of the black tank box. This line is a mix of 1/2" PEX and clear plastic beginning at a barbed elbow screwed into the tank at a flange on the street side of the tank near the bottom. (Note: Near, not at or on the bottom. The tank never fully drains through the petcock. Never!) There is an additional elbow in this line which creates a zig zag pattern and presumably allows the tank to move a bit without breaking the drain line.
d. The water pump feed line which is 1/2" PEX attached to an elbow that is screwed into a flange immediately adjacent to the drain fitting.
3. Also attached to the outside wall of the tank on the street side is a flexible printed circuit board. This is the water level sensor. It is connected to the trailer wiring with two wires.
4. Finally, this space contains the low point drain risers. These two, vertical, 1/2" PEX pipes connect to the brass petcocks on the underside of the black tank box and to the trailer's hot and cold distribution system in the space under the fridge.
The tank box is lined with 1/2" styrofoam panels for cushioning and insulation. I'm not convinced that 1/2" of low density styrofoam provides much cushioning or much insulation, but that's what is there. The ends of the water tank box are packed out with several layers of styrofoam wrapped in duct tape to limit the distance that the water tank can shift in the larger tank box. Crude, but evidently effective.
The space is difficult to photograph, but here are three shots that show what you might see:
Of these fittings, it would be possible to tighten the connections for the water fill line to its fitting or the vent line to its fitting without removing the tank. It may be possible to replace those fittings if cracked or loose also. If either of those fitting are causing your leak, they wouldn't leak for long before the water level fell below the point of leaking and the leak stopped. I can not envision fixing leaks at the drain or pump feed fittings effectively without removing the tank. If someone has accomplished that, please add to this thread to point the way!
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