Men sit back cause here it comes. My sister and I, yep 2 females puchased a 2005 Keystone Montana 5th wheeler for 80 year old mom. After connecting the city water and 2 weeks later after many experiences (various stories) we have a major leak that comes out underneeth trailer. We unscrewed 2 bolts from black cover underneath by front tires and water is now draining from that point- shut water off. It seems that when the water hose is on and the kitchen sink is on, is when the problem begins. Not toilet water and havent used shower yet. Yes we emptied the gray and black tanks (another leason learned hardway. We paid to move the trailer here which is not full for fulltime use and we dont know where to go from here. Is there another tank that we are not aware of and perhaps its full? do you think a hose detached? Whats the best access besides taking all the bolts off and exposing the entire underside of the trailer? I appreciate all advise! Thank you in advance for your time.

Some (not saying yours does) 5th wheels have three tanks....1 black, 1 grey (shower/bathroom sink) and 1 'galley' (kitchen sink). Each has their own dump valves. Sometimes the galley one is not with others and is back behind tires.But if tank was full it would back up into kitchen sink.The drain line from sink to tank could be cracked/broken.The undercover is plastic. Look under kitchen sink and see where drain line runs.Then with a mental picture of that location go outside and under rig.You can cut a three sided window in the plastic cover (the non-cut side should be towards front-----2 parallel cuts lengthwise front to back with a rear cut across then pull flap down). This will give you a visual on the source of leak.Got to find it before you can fix.......plus you need to get the water out of there and give it a chance to dry out (mold/mildew-----food debris if from kitchen sink)The three sided flap can be taped back shut after repairs. Lots of flaps out there cause of needs to repair with enclosed/covered underbellies.

Thank you for your quick reply. We will take a look!

We have 3 tanks on our 5'er. We have 2 valves under the bathroom area (black and gray from shower and bathroom sink) and one valve that is a PITA to get to - it's under the slide (gray from kitchen). That is probably your problem, also. Hope you can find it quickly. If you can't, are you in a campground with other campers. Do you know any of them and could ask? Is there anyone that walks around the campground that seems to be friendly? Is there a camphost? Those would be my suggestions.

Did your rv come with manuals. If it did I would start by reading the manuals front to back. These units can be fairly complex. Between your manual and the forums, you should be a veteran in no time. Make sure if you live in an area that freezes that you understand the importance of draining your water systems and how to do it. good luck and enjoy the new rv.

With or without a galley tank under your trailer your leak is much more likely to be coming from a pressure water line. You say it leaks most with the kitchen sink water running so it could also be the drain from the sink to the tank (whether it's a galley tank or all in one gray tank).Good luck / Skip

Major water leak coming out underneath trailers black cover

13 Replies

InspectorMark
Explorer
Feb 12, 2014
Something vary similar happened with my 2002 Keystone Laredo 5th wheel.
When we used the kitchen sink water would drain out from various areas under the unit. Even after removing sections of the plastic under sheathing I could not tell where the water was leaking from.

I was worried that the gray water tank was cracked but it turned out that the drain pipe from the kitchen sink sheared off where it entered the gray water tank. It entered the tank from the top so this could not be determined until the tank was dropped.

This was a bigger project than I wanted to do laying on my back in the dirt at a seasonal site. I took it to a repair shop and the cost was about $600. This was two years ago and its been fine ever since.
Old-Biscuit
Explorer III
Feb 12, 2014
dhsmontana wrote:
Thank you everyone. Great suggestions and we can look Friday and let you know what we see. I did look at the manuals but unfortunately it doesn't give me enough info. We did locate another handle under the slider by tires black handle. Manual doesn't say what it is. I was afraid to pull it as I thought it is a manual lever to disengage the auto slider. Old biscuit I think this is what your referring to. I'm going to pull it. One question should it stay open? Thanks you.

Handle look just like the other dump valve handles?
It is most likely the dump valve for galley tank (kitchen sink).
Tank is FULL.
Tank full and kitchen sink NOT backing up means water is running out of:
*cracked drain line from sink to tank
*loose fitting on drain line from sink to tank
*out of top of tank where drain line from sink connects......grommet/gasket bad/pushed out of place.

Drain the tank......you can leave it open (unlike black tank.never leave open). Just be aware that "sewer flies" can come up hose and set up house in the tank, odors can come inside rig IF sink 'P' trap goes dry or 'air admittance valve' should stick open (small vent device on sink to tank drain line just after 'P' trap)

Until you open the underbelly cover ( 3 sided window) and locate WHY water was leaking out/fix that problem) you need to either leave the galley tank drain valve open OR dump tank frequently so that MORE water doesn't leak into underbelly.
wa8yxm
Explorer III
Feb 12, 2014
Since it only happens with city water and sink (I'm thinking it only happens with sink) I suspect a drain or gray tank issue,,, If you have 3 tanks that one is the Gray. If you have a "T" handle like the black tank dump handle if you can see where the rod goes. If it goes to a gate valve in the 2-3 inch class (Like the black tank dump) that's your 3rd waste water tank (or perhaps the 2nd if it is a trailer, some of them have a 2nd valve in teh dump line

Black Valve, Gray Valve, Wash Valve all connected via a manifold to a Main Dump valve which must be opened first.
John_Joey
Explorer
Feb 12, 2014
Go to the park office and ask who they recommend as a mobile RV tech. Give them a call. If you're not in a park then give the nearest one a call and ask the same question of them.

It will be money well spent, and you might need them again in the future. At that point you will have a working relationship going.
Merrykalia
Explorer II
Feb 12, 2014
dhsmontana wrote:
Thank you everyone. Great suggestions and we can look Friday and let you know what we see. I did look at the manuals but unfortunately it doesn't give me enough info. We did locate another handle under the slider by tires black handle. Manual doesn't say what it is. I was afraid to pull it as I thought it is a manual lever to disengage the auto slider. Old biscuit I think this is what your referring to. I'm going to pull it. One question should it stay open? Thanks you.

I'm not Oldbiscuit, but yes, that is the handle. Make sure you are hooked up to the sewer and then pull that handle. You should hear it gushing out. If not, then that is not the problem.

Do NOT leave the handle open. It will allow sewer gases to get into the RV and it will smell awful, but also, it is gas, so there is always a slight possibility of an explosion. (yes, pretty slight possibility, but it is there).

I hope you find that this is the problem.
westend
Explorer
Feb 11, 2014
If I could make a suggestion---can you get some pictures up here of the areas and issues you're trying to fix. "handle under the slider by tires black handle" is pretty descriptive but that handle could be for any type of use and pulling it may or may not be connected to your leak problem. I'm guessing it's not since you stated that the leak occurs when the faucet is used and there is water pressure in the shore water hose. This indicates a leak in the fresh water supply piping rather than a drain issue but that could also be your problem if the tank is full. Have you recently drained the waste tanks or are they permanently open to a fixed drain?
dhsmontana
Explorer
Feb 11, 2014
Thank you everyone. Great suggestions and we can look Friday and let you know what we see. I did look at the manuals but unfortunately it doesn't give me enough info. We did locate another handle under the slider by tires black handle. Manual doesn't say what it is. I was afraid to pull it as I thought it is a manual lever to disengage the auto slider. Old biscuit I think this is what your referring to. I'm going to pull it. One question should it stay open? Thanks you.
1492
Moderator
Feb 11, 2014
Moved from Forum Technical Support
skipnchar
Explorer
Feb 11, 2014
With or without a galley tank under your trailer your leak is much more likely to be coming from a pressure water line. You say it leaks most with the kitchen sink water running so it could also be the drain from the sink to the tank (whether it's a galley tank or all in one gray tank).
Good luck / Skip
winniman
Explorer II
Feb 11, 2014
Did your rv come with manuals. If it did I would start by reading the manuals front to back. These units can be fairly complex. Between your manual and the forums, you should be a veteran in no time. Make sure if you live in an area that freezes that you understand the importance of draining your water systems and how to do it. good luck and enjoy the new rv.