Tank leakage problem?

[kingdaddy]

While leaving a local RV park after a 3 week stay (our house was being shown for sale) I noticed a pretty fair amount of water leaking from several locations around the underbelly cover!
No leaks of any kind while hooked up at the park, and I followed my usual routine emptying the tanks before leaving. I ignore the tank level indicators of course, and go by the visual I get with my clear sewer fitting.
The only thing different was that I tried using the black tank flush for the first time and I'm wondering if something didn't work right or if I did something wrong? Never used it before, but it seemed to be pretty effective judging by the additional sludge that drained after the initial black tank draining.
There are two gray tank valves (one in the convenience center and one near the main slide on the frame) and of course the black tank valve also in the convenient center. All tanks seemed to be empty upon leaving so I'm puzzled as to where this water was coming from? Kinda smelled like it was black tank water...
The only thing I can figure is that it has something to do with using the tank flush... any ideas?

[DQDick]

There is a backflow preventer valve in your water line to the black tank flush that is a known problem. It's usually found under the sink or behind a bathroom wall. Many have replaced it and some, like us, have taken it out altogether and replaced it with one we use on the outside.

[jcurtis934]

I assume your model has two separate areas to the belly, front being 50 gal shower grey and 50 gal black...rear section fresh water tank and 40 gal galley grey. So was the water coming from front or rear? Black tank would be real smelly...grey mostly just stinky. Afraid you are going to have to do a bottom section drop to really notice anything here. John

[kingdaddy]

My model and year has a 50 gal waste (black) tank and 93 gal gray. But it has two gray tank valves...I assume the tank is partitioned for some reason.
The water was coming from the front area near the landing gear because I was parked on a down slope as I was checking out of the park.
So if the back flow prevention valve was not working properly, how would this allow water to accumulate outside the tank? The tank itself was completely drained before pulling out of the site...
Also, does anyone know whether the tank flush is just for the black tank? The sticker says to make sure the valve is open, but now sure if the gray tank valve should be open or closed?
Thanks for the advice!

[DQDick]

Flush is black tank only and you do have two separate gray tanks. The valve for your second grey tank is most likely located just in front of your street side tires protruding thru the frame. The 93 grey you've been told is adding the two separate tanks together. If you're not emptying the second grey tank that probably is your problem.

[kingdaddy]

Thanks Dick, yes I knew about the "hidden" gray tank valve and do empty that one as well. It makes sense that the 93 gal. figure on the Keystone website is simply the total of both tanks (no actual mention there of two separate tanks).
After talking to a few folks at the RV park and nearby RV store (parts not sales) I am thinking I have a problem with the plumbing on the black tank flush system...maybe a bad fitting or (as you mentioned) a problem with the back flow device?
I will certainly be posting the results for the benefit of others of course...

[Richard Bruno]

I experienced the flush system check valve leak early on. I took awhile to trace the plumbing and find the valve. It was locate behind the shower wall and was accessible from the front closet. The valve was cracked at the inlet connector. I ordered a replacement from the valve manufacturer ($10). The replacement leaked too so I inserted an elbow in its place.

[Art-n-Marge]

I will notice some water coming out from the bottom middle of our rig if we go more than two days without emptying our galley tank. I am guessing that the water is coming from a leak where the drains go into the tank on the topside. Of course, I can't get to that so we just make sure we empty both gray tanks about every two days. If I stay on that schedule I don't see any water. The Black tank gets emptied every six days, followed by both gray tanks to keep all the drains clean (I always follow a black tank flush with grey tank flushes, just to keep things cleaner.

BTW - my sensors went kaput months ago and this every two day interval for the greys helps a lot. If we have guests (daughter and family or son and family or others), then I just empty the tanks every day, since the sensors don't work well and I don't want to risk overflowing past the fill plumbing.