furnace problems

[Syndi]

Help! I have a water leak and have narrowed it down to the area between the furnace unit and the outside wall. I'm in a 2006 3400 Montana 5th wheel. I had noticed a small amount of water between the kitchen slide out and the pantry in the corner. When I opened the basement and removed the cover to the furnace I noticed small amount of evidence of water on wood under area between furnace and outside wall of 5th wheel. There are 4 water lines that feed between unit and outside wall and this is where I think the leak originates. I need to remove the furnace to examine these but having trouble removing it. Any ideas?

[Carl n Susan]

Sounds like a leaky anti-siphon back flow device for the black tanks flush system. Do Search, there will be a lot of hits.

[Daryles]

Is there an access panel in the bottom of your pantry? There is in mine 3130re. Behind it is the water heater and furnace.
Maybe remove the basement wall?
Looking at the Floorplan you have a garden tub there? Maybe a leaking fitting?

[DQDick]

I'd bet on the backflow preventor first. It should be either under the bathroom sink or in the wall somewhere with a small access panel. If not that then I would check the water heater. Mine just started to rust thru and it's only three years old.

[Syndi]

Originally Posted by Daryles

Is there an access panel in the bottom of your pantry? There is in mine 3130re. Behind it is the water heater and furnace.
Maybe remove the basement wall?
Looking at the Floorplan you have a garden tub there? Maybe a leaking fitting?

I checked there first. Replaced a 90 for the hot water several months back and it’s dry. The furnace is under the tub area and you can see the side of it well when you take the access panel off in the basement. The hot water heater is a good ways away from this problem. The pantry is in the other side of the access from the basement and it does not have a access panel in it. I may have to change that. There is not a access panel from the outside either.

[Syndi]

No. I can not find a access excerpt from that basement side. I’m also having a lot of problems trying to loosen the vent that goes out to the outside of the unit. I am considering cutting a access thru the lower pantry area

[Syndi]

The hot water tank is about twenty feet from the problem. I have pex tubing thrust the unit. I find if I have a problem it’s usually in a 90 or other connector The bathroom sink is on the other side of the unit and I could not find any wet areas along the path between the two

[Syndi]

I have already replaced the hot water heater a couple of years ago. No problem with any wetness around there. Went outside under the unit and tried to access the problem from the outside and underneath unsuccessfully. I am stubborn and will pay for a traveling repair person only as a LAST RESORT Still want to hear ideas. Did not know that there was a anti siphon back flow prevent or. It seems as the problem is in a area in between the part of the furnace that is attached to the outside of the unit and the unit itself. There are 3-4 per lines there and I can’t get to them to see the connections. It looks like they are going from the bathroom tub and sink and then pass in front to the furnace going back toward the hot water heater and cold water inlet. I just can’t see why they would put them in a area that you can not access. I will be trying to find the anti-siphon back flow connection and check that out. Thanks

[Carl n Susan]

In the 2006-2008 series (and maybe others) of the 3400, the black tank anti-siphon valve is behind the shower wall and the pantry. There may or may not be an access panel in the pantry. Also the sliding door will block access, so be sure to close the door when looking for the valve.

You wrote there are 4 water lines running up the wall. This yet another clue that there is an anti-siphon valve in play here. There are lines 2 for the shower (hot & cold) and 2 for the anti-siphon valve (in & out). Here is a link to an old Thread (with pictures) about your exact problem.
https://www.montanaowners.com/forums...ad.php?t=36316

If digging in the wall doesn't excite you, then try the procedure most of us have started using. Remove the rear wall in the basement, locate the two lines, cut the Pex lines to/from the valve and tie them back together with a Shark-byte 90 degree fitting. Put an anti-back flow adapter inline in the convenience center and you are done.

[Syndi]

Ok. Found the back flush valve I. The wall in the pantry but I can not tell of any moisture around it. How do I make it work to see if there is a problem with it? In other words. What makes it work or leak. Does it have water pressure on it at all times? And is there water running thru this line going g to the shower? It’s very hard to see and I will have to open the wall to replace it if I can see that it is needed

[Carl n Susan]

The only time the valve sees water is when you are flushing/rinsing your black tank. You do that right? You should never leave a hose connected to the fixture in the CC. One should remove the hose after one is done flushing. The valve is not built to handle continuous pressure. Removing the hose removes the water pressure on the valve.

[beekeeper.va]

Is is at all related to rain?

[Daryles]

Two excellent tools.
1. Ryobi multi tool plus. With the half circle blade.
https://www.amazon.com/dp/B07N1QNHVT..._8Ms6Fb5K9DR7M
You can make precise cuts without damaging objects behind it. I.e. making acces holes in the pantry.
2. An endoscope you can attach to a laptop OR your phone. This you would find useful now to track down that leak.
https://www.amazon.com/dp/B07PBF6DX5..._OUs6FbVTG93DM

[sduchien]

Can anybody tell me where the anti-siphon valve is in my 2020 3740fk? I can’t see one under the bathroom sink.

[DebNJim B]

Originally Posted by sduchien

Can anybody tell me where the anti-siphon valve is in my 2020 3740fk? I can’t see one under the bathroom sink.

Yours may be like mine and behind the convenience center. Removable access panel in basement. I have the front living room but other parts of the layout, ie. bathroom and black tank location, are similar.

[Syndi]

No. I can not find any correlation to shower, rain, toilet being flushed, tanks being full, drained, or any thing else. Drives me nuts

[Syndi]

That has not been done any time that I saw water. Thanks for the info though