I have a 2018 Coachmen Leoprechaun 21QB. Have taken many trips. Recently I filled my fresh water tank, waiting in the driveway for it to fill. When I heard the overflow water running onto the driveway, I looked underneath and it seem water was also splashing out of somewhere right by the overflow drain tube. Shut off the water and didn't think much of it. I did not use the presurre regulator like I usually do. Later in the day while on our trip I discovered that the water tank was completely empty. (drain valves were shut tight) Also, the black water tank that was emply when I left was now full of water.As I drove to destination, I spent the whole time worrying about did I split my water tank of bust a pipe somewhere? I was so worried about a major repair needed. Arrived destination that day, and immediately went to work diagnosing. I filled water tank with a hose, until the overflow started running onto the ground and shut off hose. NO leaks anywhere, all normal. For 4 days now I have used the fresh water system (and I had drained black tank). Water pump on full time during the 4 days. Only thing I thought was odd is that when I filled tank at my destination, when it began to overflow, the overflow ran for a while onto ground after hose shut off- about 3-5 gallons flowed out. But all seems normal now. All plumbing, pump, heater, etc. work fine.SO, what on earth happened at beginning of trip when fresh tank emptied from full, and black tank went from empty to full of water, and all seems perfect now??? Thank Dave

Happened to us one time when the toilet valve did not close completely, letting fresh water into the toilet, until the bowl filled, then via overflow into the black tank. Might watch for that.

What happened was simple. Some RV's the overflow tube IF when overfilling and water comes out the overflow tube, it starts a SIPHON. When you shut the water OFF, the siphon continues until the water reaches a level where air can then interrupt the process. BUT, this is IF you connected to the Water FILL port. What you did was, you connected to the BLACK TANK FLUSH by mistake. Luckily, the top of the tank is NOT sealed correctly and the overflow ran off the top of the tank. OR, most common, you have "POPPED" the 3 inch toilet down pipe that goes from the toilet to the top of the tank LOOSE and the 3 inch down pipe is NOT sealed to the tank. You can sometimes see this when looking down the toilet with the toilet valve OPEN and no water running. I would flush the tank a few times and then refill the tank with the Black tank flush and monitor the liquid level by watching thru the toilet> have someone outside to turn OFF the water when the water comes UP that 3 inch pipe. If the water does NOT come up that 3 inch pipe the downpipe is not connected to the top of the tank and you will get odors since the tank is not sealed correctly. Doug

Black tank plumbing is simplistic only involving the toilet and a vent pipe.You did what many have done, screwed hose into tank flush.In fact, there was a post earlier this year on this forum where someone flooded the interior of trailer with sewage. It started up the vent tube and when toilet was attempted to flush, it came exploding out.....I could only imagine.

I forgot to mention. There is a FLOOD test that is done when you PDI(pre delivery inspection) of any RV when sold. That involves filling the Gray and Black tanks overfull until water stands in the shower and water stands in the down pipe of the toilet. There should BE NO LEAKAGE of water. If there is the system is not water/air tight and must be fixed. SO, if the OP had water flowing underneath onto the ground, his system is not up to spec and this means it is not air tight to prevent sewage odors from getting into the interior or outside. Doug

Thanks for replies. I am sure I put hose into correct fill valve to fill fresh tank. It took a long time to fill fresh tank, and monitor showed it full. Thanks so much but I'm stumped (I've only used black water flush valve once and it makes a distinct rushing water sound, so I am sure I was filling fresh tank. I was nearby the whole time). Thanks! Dave

Coachmen Leprechaun fresh water tank | Good Sam Community

dougrainer
Nomad
Aug 01, 2020
mchero wrote:
dougrainer wrote:
I forgot to mention. There is a FLOOD test that is done when you PDI(pre delivery inspection) of any RV when sold. That involves filling the Gray and Black tanks overfull until water stands in the shower and water stands in the down pipe of the toilet. There should BE NO LEAKAGE of water. If there is the system is not water/air tight and must be fixed. SO, if the OP had water flowing underneath onto the ground, his system is not up to spec and this means it is not air tight to prevent sewage odors from getting into the interior or outside. Doug

My rig will fail the test!
We have a vanity on the full wall slide. The drain line on the slide slips inside the pipe on the rig. It's not a water tight seal and will dribble IF the gray tank gets too full.

AND, that will allow tank odors to migrate to the Interior of the RV. More so in transit, rather than camped. Doug
mchero
Explorer
Aug 01, 2020
dougrainer wrote:
I forgot to mention. There is a FLOOD test that is done when you PDI(pre delivery inspection) of any RV when sold. That involves filling the Gray and Black tanks overfull until water stands in the shower and water stands in the down pipe of the toilet. There should BE NO LEAKAGE of water. If there is the system is not water/air tight and must be fixed. SO, if the OP had water flowing underneath onto the ground, his system is not up to spec and this means it is not air tight to prevent sewage odors from getting into the interior or outside. Doug

My rig will fail the test!
We have a vanity on the full wall slide. The drain line on the slide slips inside the pipe on the rig. It's not a water tight seal and will dribble IF the gray tank gets too full.
dougrainer
Nomad
Jul 30, 2020
kellem wrote:
dougrainer wrote:
The only other possibility is, Your Toilet water valve dump blade was stuck slightly open and when you were filling the Fresh Water, the water was going into the Black tank thru the toilet. Maybe that is why it took a long time to fill the Fresh tank. Doug

Solid theory but the dump valve being stuck slightly open " happens quite often " shouldn't allow the toilet to continue to flush but must admit......I'm stumped if hose was indeed hooked to fresh water.

NOT DUMP VALVE. The DOWN knife or ball in the toilet that seals the toilet bowl from the tank. That opens when you flush the toilet. Doug
DrewE
Explorer II
Jul 30, 2020
kellem wrote:
dougrainer wrote:
The only other possibility is, Your Toilet water valve dump blade was stuck slightly open and when you were filling the Fresh Water, the water was going into the Black tank thru the toilet. Maybe that is why it took a long time to fill the Fresh tank. Doug

Solid theory but the dump valve being stuck slightly open " happens quite often " shouldn't allow the toilet to continue to flush but must admit......I'm stumped if hose was indeed hooked to fresh water.

Doug's talking about the flush valve in the toilet, which also actuates the slide/flapper thingy "dumping" the toilet bowl's contents into the black tank, rather than the black tank dump valve, for emptying the black tank. Indeed, the latter would not in any way cause water to enter the black tank via the toilet, as you note.
kellem
Explorer
Jul 30, 2020
dougrainer wrote:
The only other possibility is, Your Toilet water valve dump blade was stuck slightly open and when you were filling the Fresh Water, the water was going into the Black tank thru the toilet. Maybe that is why it took a long time to fill the Fresh tank. Doug

Solid theory but the dump valve being stuck slightly open " happens quite often " shouldn't allow the toilet to continue to flush but must admit......I'm stumped if hose was indeed hooked to fresh water.
dougrainer
Nomad
Jul 29, 2020
The only other possibility is, Your Toilet water valve dump blade was stuck slightly open and when you were filling the Fresh Water, the water was going into the Black tank thru the toilet. Maybe that is why it took a long time to fill the Fresh tank. Doug
dougrainer
Nomad
Jul 29, 2020
DavidRue wrote:
Thanks for replies. I am sure I put hose into correct fill valve to fill fresh tank. It took a long time to fill fresh tank, and monitor showed it full. Thanks so much but I'm stumped (I've only used black water flush valve once and it makes a distinct rushing water sound, so I am sure I was filling fresh tank. I was nearby the whole time). Thanks! Dave

From your story, I think you used the Black Flush TWICE:B
DavidRue
Explorer
Jul 29, 2020
Thanks for replies. I am sure I put hose into correct fill valve to fill fresh tank. It took a long time to fill fresh tank, and monitor showed it full. Thanks so much but I'm stumped (I've only used black water flush valve once and it makes a distinct rushing water sound, so I am sure I was filling fresh tank. I was nearby the whole time). Thanks! Dave
dougrainer
Nomad
Jul 29, 2020
I forgot to mention. There is a FLOOD test that is done when you PDI(pre delivery inspection) of any RV when sold. That involves filling the Gray and Black tanks overfull until water stands in the shower and water stands in the down pipe of the toilet. There should BE NO LEAKAGE of water. If there is the system is not water/air tight and must be fixed. SO, if the OP had water flowing underneath onto the ground, his system is not up to spec and this means it is not air tight to prevent sewage odors from getting into the interior or outside. Doug
kellem
Explorer
Jul 28, 2020
Black tank plumbing is simplistic only involving the toilet and a vent pipe.

You did what many have done, screwed hose into tank flush.

In fact, there was a post earlier this year on this forum where someone flooded the interior of trailer with sewage. It started up the vent tube and when toilet was attempted to flush, it came exploding out.....I could only imagine.

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