04 MB Fresh Water tank leaking

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04 MB Fresh Water tank leaking

December 10, 2021, 05:57:30 pm

I noticed our 2004 MB fresh water tank is slowly seeping water in the last couple of days. I checked all water fill inlet and pump outlet, these locations are dry. The drain valve area is also completely dry. Water is seeping out from the joint seems between floor and outside wall.

I removed the kitchen drawers and the drawer below the fridge. The floor areas in the forward and rearward of the tank are completely dry. I could not see the tank side wall attached to the outside wall. I also put a borescope through the water inlet but could not direct to the camera to any particular area and the opening is very small and the tank is huge.

Did anyone experience this kind of leakage. I wonder whether it is caused by a stress crack in the water tank. Yesterday, I completely drained the tank and wiped all affected floor outside area clean and dry. Today, I slowly fill the tank while observing the water level carefully, stopped at just wet bottom, to about 1/10 full, 10% full and 20% full, then wait for about an hour at each time. There was no water seeping out until 20% full. I think that is the hydrostatic pressure causing the leak. I never experienced anything like this, anyone have some insight?

It will be a huge job to replace the tank but I am not sure even how to fix it. Similar to Tedeboy's posting two years ago, I put in a lot of improvements to this rig so retiring it at this time is not an option. Driving to mothership from our current location of MIami, FL will be challenging as well.

Thank you in advance for any suggestion.

Re: 04 MB Fresh Water tank leaking

Reply #1 – December 11, 2021, 10:14:19 am

The picture shows water slowly seeping down on the inside surface of the 2004 MB side skirt in the area of fresh water tank. The black tank is also suspended in this area shown by the insulating foam. There is no leak from black tank which is below of the floor pan.

Did anyone ever replaced a fresh water tank by him/herself in a MidBath LD?

Re: 04 MB Fresh Water tank leaking

Reply #2 – December 11, 2021, 10:36:13 am

I haven't, but I own a Mid-bath and suspect it would be a very big job.

If this rig were mine, I would consider removing the stove which would give you access to part of the top and possible the space behind the water tank. This would allow for a better inspection.

After that, if I was convinced the tank itself was leaking, I would consider cutting an inspection port into the top of the tank and using that to try and determine where the leak might be coming from.

This might seem obvious, but keep in mind that the water fill is in that area and you could have a leak of some sort related to that. It sounds unlikely given what you describe, but I would be interested in ruling out every possible alternative before cutting into the water tank.

If you can find the leak point, you might be able to repair it from the inside via the inspection port.

These are all ideas from someone who hasn't seen or solved this problem before. I am sure the removing and replacing the entire water tank is best avoided if at all possible.

Rich

Re: 04 MB Fresh Water tank leaking

Reply #3 – December 11, 2021, 10:42:09 am

We had the fresh water tank leak at the connector to the water pump last year. Took it in to the Lazy Daze shop and had the repair done. Todd said this type of leak is rare but they took the cabinets under the sink apart, fixed the leak and put everything back together. They know what they are doing.

Re: 04 MB Fresh Water tank leaking

Reply #4 – December 11, 2021, 10:48:03 am

For what it is worth, years ago I had a 40 gallon water tank in a camper and it developed a very bad leak. Removing the tank was impractical, so I completely drained the tank, got as much access as possible, and very gently applied some air pressure to the tank through a fitting. Using a spray bottle with soapy water, I found a crack in the lower corner of the tank.
I don't remember what I sealed the crack with, but I slathered the stuff over and around the crack and it never leaked again.

Good luck with your leak.

Harold

Re: 04 MB Fresh Water tank leaking

Reply #5 – December 11, 2021, 11:34:19 am

cli288 (a name would be helpful),

Based on where you are seeing dripping water, I am wondering why you think it is the fresh water tank that is leaking? I have a 2003 midbath and the area you are seeing water dripping sounds like it may be closer to the shower and toilet area. Perhaps a water fitting to the shower, toilet or even the lavatory sink may be the culprit. Heck, maybe it is the kitchen faucet connection. I would be hopeful it is the kitchen faucet because that may be the easiest area to work on.

I think that before I start removing cabinets and appliances to gain access to the water tank, I would try parking the rig with it tilted towards the front and to the passenger side to see if the leaking water appears in the kitchen area. I would expect water from the tank would flow somewhere near the tank in the living area.

Another thing to do would be to drain the fresh water tank and connect to the city water connection to see if the water leak still appears. If so, that would rule out the fresh water tank.

When I installed a new waterpump one of the fittings on the pump was not attached properly. The water from the tank dripped out of the rig directly below the waterpump, not towards the rear.

Good luck! I hope it is something simple to remedy.

Steve K

Re: 04 MB Fresh Water tank leaking

Reply #6 – December 11, 2021, 02:20:17 pm

You definitely need to investigate all potential sources of the leak before tearing into it.
If you find the leak is a crack, you have three choices, replace the tank, remove the tank and have the crack hot-air welded, or glue the crack with structural epoxy, made for polypropylene and polyethylene.
I would consider placing a patch over the crack, made of plastic or sheet aluminum, as well as opening the crack up slightly to force the glue into it. Eternabond tape would also make a good patch over the glued crack.
McMaster-Carr

Larry

Re: 04 MB Fresh Water tank leaking

Reply #7 – December 11, 2021, 04:44:56 pm

Thanks to everyone for point me to the right direction. I removed the two drawers next to the stove to check the fresh water inlet area, both the fill connector and the vent connector are dry, no leak. Then I tilted the LD by raising the passenger side higher, Guess what, now water is showing up on the floor. It is most likely from the bottom or lower walls of the fresh water tank. I plan to remove the stove for further inspection. I realize this is a huge project but there is no other way to ignore this leak. I may have to delay the repair until we are back to Michigan to start the repair or replacement as most of my tools are at home, not with me in the winter camping ground.

Thanks again for everyone's help, particular to Steve for suggesting tilt the LD!

Re: 04 MB Fresh Water tank leaking

Reply #8 – December 12, 2021, 07:27:01 am

CLI288, I have a couple more thoughts about your leak. (I am still not convinced it is your fresh water tank though...)

To see more of the fresh water tank, you can easily remove the wood trim in the cabinet under the drawer which is beneath the refrigerator. That will allow you to see the front end of the water tank and possibly some of the tank along the outside wall. At least you may be able to see if there is a wet area.

It seems you have looked at the tank where the drain valve is, the water fill, and I would hope you looked at where the water line between the water pump and the water tank attach. What about the threaded fitting on the water tank itself. Also, those sensor wires for your read out are attached to fittings that I *think* are inserted into the tank. Possibly a small crack there?

I hope you can figure this out without tearing that area apart.

Steve K

Re: 04 MB Fresh Water tank leaking

Reply #9 – December 12, 2021, 01:52:12 pm

Quote from: rich - December 11, 2021, 10:36:13 am

If this rig were mine, I would consider removing the stove which would give you access to part of the top and possible the space behind the water tank. This would allow for a better inspection.
Rich

Removing the stove and the drawers next to it might provide the access needed to remove the tank, doing so mayl provide a better view of the source of the leak.
Removing the stove isn’t a big job. Shut off the gas and then light a burner to bleed off the remaining gas. Remove the top of the stove and disconnect the stove’s gas supply fitting. Remove the four screws under the cover and then slide the stove out.
It weighs around 45-lbs and can be put on top the dinette table.
With the drawers removed, the drawer slides can be removed if access to the tank under the drawers is needed.

I would call the Mothership to find out how they would remove the tank, no reaason to reinvent the wheel.

Larry

Re: 04 MB Fresh Water tank leaking

Reply #10 – December 15, 2021, 12:49:25 am

I had a similar leak in my MidBath that was driving me crazy. It turned out to be the plastic large particle filter. It is the plastic part upstream from the water pump and downstream from the water tank. Suspended below the sink. It had a hairline crack along the threads on the backside. I was underneath looking for something and only accidentally found it. It only leaked when the water level in the tank was higher than the filter. Between a 1/4 and 1/2 tank as I remember.

Re: 04 MB Fresh Water tank leaking

Reply #11 – December 15, 2021, 12:56:15 am

This is the replacement part. I took the picture when I was winterizing so it is full of pink antifreeze instead of water. Makes it easier to see though. If this turns out to be your problem it is easier to replace than a water tank.

Re: 04 MB Fresh Water tank leaking

Reply #12 – January 23, 2022, 11:13:27 am

Thanks to everyone helping me resolve this difficult issue. I think I finally got it nailed. Following the advice, I did remove the cooktop and oven assembly to access the fresh water tank. After careful inspection, the tank was in good condition, does not have any leaks. I then turned my attention to potential outside leak sources. I resealed the kitchen window above the fresh water tank. Unfortunately that did not stop the intermittent leak. I then inspected the fresh water inlet but did not find any leak either. Finally I opened the outside shower door. I found some residual water there but there was no leak from the shower assembly or the valves. However, the rubber weather-strip seal appeared to deteriorated badly, it shrank and formed a small gap in the bottom so water can directly leak into the space between the aluminum shell and the insulation behind. The weather-strip lost its function and can no longer seal rain water from outside. Since the leak is small it took a long time before showing up in the bottom of the vehicle skirt. After I resealed the weather-strip of the shower compartment with silicone, I sprayed water and waited hours to confirm the leak has stopped.

Sharing this experience to other MB owners, so they can take a look if their outside shower compartment seal may also require attention.

Re: 04 MB Fresh Water tank leaking

Reply #13 – January 23, 2022, 11:48:38 am

Thanks for letting us know how you resolved this water problem. I'm sure other owners will check this out, and I'm glad that you didn't find a problem with the water tank. RonB

Re: 04 MB Fresh Water tank leaking

Reply #14 – January 23, 2022, 09:30:21 pm

"After I reseal the weather-ship of the shower compartment with silicone, ..."

When I read the above line in your post a shiver ran up my back. There have been multiple posts on this forum advising that one should NEVER use silicone. Once having done so no other sealant will stick to the old repair should that become necessary. I will not have silicone in or near my rig!

Re: 04 MB Fresh Water tank leaking

Reply #15 – January 24, 2022, 01:10:24 pm

I understand and appreciate your concern and agree with you for the general case. Silicone is not suitable for seals in the area to be re-sealed. However I bought a small tube of silicone just for this application where I will not intend to paint. I could not remove the old weather-strip as it will crack into powders but its residue still stick to the aluminum sheet formation. I ruled out the 3M 5200 as it may be too rigid when I close the door. The silicone calk was only applied in this localized area and no where else. The silicone calk's excellent low energy surface helps to repel water when the door is closed, preventing future leaks into this compartment.

Being a chemical engineer in my previous life working on polydimethylsiloxane (the base material in silicone) in a couple of years in the graduate school, I think I know the properties and limitations of silicone sealants. Rest assured, I will not do anything to harm my rig in the long term. I also want to emphasize one can chose unique property of a material for a specific application.

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