Keystone Cougar

You should add some bleach about 2cups and fill the fresh tank let stand 3-4 hours drain and repeat...Then flush with a full tank of water 2 more times...now the tank should be as clean as You can get it...I do this every time I use the trailer the water may smell a bit of bleach but that will not have any lasting effect...We use the tank water for showers and dish washing but use bottle water for cooking and drinking after all the trailer sits for a lot of the time and water can turn nasty...

Thanks for the suggestions, I bought the unit used and the black and grey tanks were showing 2/3 full the flushed them well and now they are reading empty. It confused me why clean tank would read full but it is probably sensors. Not going to lose any sleep over it.

When we picked up our new TT last year, the fresh water tank was 1/2 or more full. Not sure if the dealers do that to test the system or if they ship them from the plant that way so there is water available to the driver during shipping.

The black and grey tanks should not have false readings unless it has been used a bit. "Slime" gets left behind on the sensors inside the tank (look like a small button) and messes up the readings and it's usually the black tank that causes it. Drivers are not allowed to use the black tank during delivery so the tank should have been pristine inside when picked up at the dealer.

As long as the black and grey tanks are reading okay after the tanks were flushed, you should be perfectly okay after that. False readings are the norm in RVs. You should always flush the black tank out as best as possible after dumping and before heading back home by using a built-in tank rinser (if so equiped), a Valterra clear backflush elbow or hand held flush wand. Some black tanks cause more false readings than other due to the shape and dimensions. Periodic cleaning using the Geo method or RV chemicals specifically for the purpose can help. The objective is to clean the sensors as good as possible.

Yes, look for a blue 1/2" PEX water pipe hanging down below the fresh water tank and open up the shutoff.

There is a pex drain line with a valve at the end under the tank protruding through the belly covering. Look under the trailer about even to where the fresh water fill is and you should see it. Open valve and drain the tank.

It just may be that the sensors in the tanks are not functioning correctly, so the monitor panel reads as such. It's common.