Black Tank Filling FW Tank?

[tgomez61]

Last weekend I was flushing my black tank using the external water hose and I noticed water draining from a (what I assumed was an overflow line) near the axel. I had the dump valve closed at this time. I didn't think the black tank had an overflow so I shut off the water and the flow stopped. I went inside to check the tank levels and the FW tank showed full...???
I drove home with the FW tank still full with plans to drain it at home to see what was in there but it's been raining pretty steady all week and I haven't had the chance to get under there...
Does anyone have a diagram of the plumbing schematics so I can see if there is any mutual connections between the black and FW tanks???

Tony
2016 26RR
SE LA

[JohnD10]

There is no connection between the black tank and the fresh water tank.

It sounds like you had the water hooked up to the city water connection and the check valve in your water pump may have gone bad, which WILL fill up your fresh water tank!

What trailer do you have...26RR tells us nothing.

[elchilero53]

The drip had nothing to do with the black water. You can cure the fresh-water overflow by turning off the city water, then turn on the pump and let it run with spigots on for a minute or so. That should clear the check valve so city water won't fill it. Then turn off the pump and turn the city water back on. That's pretty much all I did and it worked just fine.

[5picker]

Are you absolutely sure you were connected to the black tank flush? You wouldn't be the first to have connected incorrectly.

As mentioned, there is no connection between the black tank flush plumbing and the fresh tank so what you've explained makes no sense.

[NMWildcat]

Originally Posted by 5picker

Are you absolutely sure you were connected to the black tank flush? You wouldn't be the first to have connected incorrectly.

As mentioned, there is no connection between the black tank flush plumbing and the fresh tank so what you've explained makes no sense.

X2

[tgomez61]

Originally Posted by elchilero53

The drip had nothing to do with the black water. You can cure the fresh-water overflow by turning off the city water, then turn on the pump and let it run with spigots on for a minute or so. That should clear the check valve so city water won't fill it. Then turn off the pump and turn the city water back on. That's pretty much all I did and it worked just fine.

I'll have to give that a try... I think maybe it was just a coincidence that I was flushing the black tank when the fresh water overflowed. I had the city water supply already hooked up... and the previous weekend was primitive camping so I had some water left in the FW tank and the check valve stuck open.
Will drain the FW tank and try hooking up to city water to see if it still transfers...

Still would like to see a diagram of the plumbing for future reference.

[JohnD10]

Originally Posted by tgomez61

I'll have to give that a try... I think maybe it was just a coincidence that I was flushing the black tank when the fresh water overflowed. I had the city water supply already hooked up... and the previous weekend was primitive camping so I had some water left in the FW tank and the check valve stuck open.
Will drain the FW tank and try hooking up to city water to see if it still transfers...

Still would like to see a diagram of the plumbing for future reference.

You don't even need to drain it (I wouldn't as it may take hours for it to fill up again).

Leave it full, then hook the city water back up and wait.

If water starts dripping out of the bottom on both sides towards the rear (and near the tires)...chances are your water pump's check valve has gone bad!

And you don't have to replace the whole water pump, but just get a brass RV check valve at Camping World or other RV parts supplier, and spend five minutes putting it in and you'll be all set!

This is what it looks like:

[5picker]

You likely won't find a plumbing schematic for your particular rig as drawings from the factory are few and far between. Dynamax is about the only division to cough up anything of value.

Here's a generic drawing that will give you a good idea.

The check valve at the city water connection (to keep the pump from pumping fresh water out the city connection) is inside the city connection itself. (You have to pull the little inlet screen to see it)

The check valve at the pump (to keep city water from filling the fresh tank) is inside the pump. (Unless an aftermarket check was installed as per the previous post)

There are other drawings available with a Google search.