On my last trip, I looked under the trailer to determine the exact amount of water left in my translucent water tank. The level could be seen.I happened to be looking on the side (port) that had the system feed and drain plug, and all looked well. However, on the other side of the tank, reaching all the way to the other side of my TT, I noticed a large area between the metal supports that was bulging down. It formed a depression inside the tank that extended a couple of inches or so lower than any other part of the tank. Obviously, water will get trapped here that will not drain from the drain plug if the unit is level.What caused this? It seems obvious that the tank should have had more supports in that area. Has anyone else ran into something like this? Has anyone been able to do anything about it?________________

On ours the FW tank bulges down when full. It is because the potable water tank is made of a more flexible white plastic stuff than the more stiff dark coloured plastic used for the grey and black tanks.Not had any issues with any water left in there when "empty" if there is any. Ours does not need any extra supports underneath. In fact a support would stop it from bulging down so where would it bulge instead or would it just not fill as much? Not a clue.

BFL13 wrote:On ours the FW tank bulges down when full. It is because the potable water tank is made of a more flexible white plastic stuff than the more stiff dark coloured plastic used for the grey and black tanks.Not had any issues with any water left in there when "empty" if there is any. Ours does not need any extra supports underneath. In fact a support would stop it from bulging down so where would it bulge instead or would it just not fill as much? Not a clue.I'm sure the bulge was caused by the weight of the water in the tank. When I observed this bulge, the tank was only about 1/5th full, so there was very little water weight.From what I remember, the tank was supported a bit better in the middle, and the left side had the feed line and drain plug on the bottom.It would have made perfect sense if the bulge had been where the feed line and drain plug was, but it was on the opposite side.Is there a chance that the builder goofed and installed the drain and feed line on the wrong side?

A goof is always possible. Our FW tank almost fell out because the rails it sits on were set too far apart. I had to shim the movable rail so it was closer to the fixed rail to give the tank full support on both the front and back ledges of the rails it hangs from.I suppose you could shim under one side of the tank where it hangs on its rails so it drains better to the other side. Not tried it. Ours is all enclosed with underbelly so it is a major PITA to get at it all.

BFL13 wrote:A goof is always possible. Our FW tank almost fell out because the rails it sits on were set too far apart. I had to shim the movable rail so it was closer to the fixed rail to give the tank full support on both the front and back ledges of the rails it hangs from.I suppose you could shim under one side of the tank where it hangs on its rails so it drains better to the other side. Not tried it. Ours is all enclosed with underbelly so it is a major PITA to get at it all.Oh, man.What's a 'PITA'?

bulge in potable water tank | Good Sam Community

Okie1
Explorer
Mar 02, 2014
Original Equipment Manufacturer
Rmack1
Explorer
Mar 02, 2014
MM49 wrote:
I plan on building a platform that supports the tank properly. I also want to make sure that the tank doesn't move. I know that the OEM installation shifted and pinched off the vent line aggravating the fill/pressurization problem.
If I can install a larger vent I might do that also.
MM49

What does 'OEM' mean?
MNtundraRet
Navigator
Feb 27, 2014
While I would not be happy with a tank that was so thin walled that it could sag like that, in the event that you might have some water settled in that depression from not being able to fully drain the tank.

If that amount of water froze inside the tank in the depression it could expand without damaging the tank.
MM49
Explorer
Feb 27, 2014
I plan on building a platform that supports the tank properly. I also want to make sure that the tank doesn't move. I know that the OEM installation shifted and pinched off the vent line aggravating the fill/pressurization problem.
If I can install a larger vent I might do that also.
MM49
Rmack1
Explorer
Feb 26, 2014
Thank you everybody.

So far, I've been impressed by the workmanship of the Rockwood division of Forest River. This is probably a design flaw. I'm going to need to get this reinforced somehow.
Rmack1
Explorer
Feb 26, 2014
kcny wrote:
PITA - Pain In The A..

Ah.
Likes_to_tow
Nomad
Feb 26, 2014
Same thing with ours, it bulged down on either side of a single channel iron support. After inspecting the support I realized it was held in place by self threading bolts into the frame. What if they failed!! I purchased two pieces of 3 inch angle iron and bolted them on either side of the factory support with grade 5 bolts with lock washers and nuts. Now the tank does not sag even when full.
It seems all trailers are now made quickly with little thought as to how they will hold up. Just get them out the door, get the check and good luck to all. Also since weight has become a large consideration in today's products, the extra pounds from extra iron would be unacceptable to a designer.
BFL13
Explorer II
Feb 26, 2014
Not impossible. He meant the air (not water) couldn't get out past the hose nozzle if you stick it in too tight and have the water on too "high"

If you do that you end up with the hose popping out and a gush of water and a half-full tank. He is right to suggest filling more slowly and with the nozzle looser in the hole to let some air out around the nozzle because the little air vent is so small.
Huntindog
Explorer
Feb 26, 2014
MM49 wrote:
Rmack1 wrote:
On my last trip, I looked under the trailer to determine the exact amount of water left in my translucent water tank. The level could be seen.

I happened to be looking on the side (port) that had the system feed and drain plug, and all looked well. However, on the other side of the tank, reaching all the way to the other side of my TT, I noticed a large area between the metal supports that was bulging down. It formed a depression inside the tank that extended a couple of inches or so lower than any other part of the tank. Obviously, water will get trapped here that will not drain from the drain plug if the unit is level.

What caused this? It seems obvious that the tank should have had more supports in that area. Has anyone else ran into something like this? Has anyone been able to do anything about it?
________________

This is a typical design flaw in most slide type RV's. The tank is flat and has a large surface area. The manufactures don't support them well enough. The water that remains in the tank is a health hazard, think Mexico! don't drink the water.

On top of the mounting problem most of the water systems suffer another problem of the potential to over pressure the tank when filling with a hose. If you stick the hose in the filler inlet there in not enough clearance for the water to bypass when full. The combination of this clearance problem and the small overfill hose the tank can be over pressured to a level that will cause damage from excessive expansion.

The procedure to fill the tank is to use a small diameter hose to fill the tank and use a slow rate of fill.
MM49
Impossible. That is what the vent is for.
MM49
Explorer
Feb 26, 2014
Rmack1 wrote:
On my last trip, I looked under the trailer to determine the exact amount of water left in my translucent water tank. The level could be seen.

I happened to be looking on the side (port) that had the system feed and drain plug, and all looked well. However, on the other side of the tank, reaching all the way to the other side of my TT, I noticed a large area between the metal supports that was bulging down. It formed a depression inside the tank that extended a couple of inches or so lower than any other part of the tank. Obviously, water will get trapped here that will not drain from the drain plug if the unit is level.

What caused this? It seems obvious that the tank should have had more supports in that area. Has anyone else ran into something like this? Has anyone been able to do anything about it?
________________

This is a typical design flaw in most slide type RV's. The tank is flat and has a large surface area. The manufactures don't support them well enough. The water that remains in the tank is a health hazard, think Mexico! don't drink the water.

On top of the mounting problem most of the water systems suffer another problem of the potential to over pressure the tank when filling with a hose. If you stick the hose in the filler inlet there in not enough clearance for the water to bypass when full. The combination of this clearance problem and the small overfill hose the tank can be over pressured to a level that will cause damage from excessive expansion.

The procedure to fill the tank is to use a small diameter hose to fill the tank and use a slow rate of fill.
MM49

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