Cummins12V98 wrote:
Every manufacturer will say to leave the valve open…..CYA.
By filling the tank and then letting the black tank valve open it's like the tide going out then it's a rinse with the sprayers then repeat then add about 5 gallons at the end.
I also travel with a clean tank with 5 gallons in it.
Also close the grey tank valve the day before travel then dump when setting up camp.
Using this method for over two years full timing the tank is spotless.
I too use the closed valve method, but I advise people don't get distracted , reason for the warning on leaving the valve open, probably more to CYA then anyone. I too use the same method, but not being able to see in inside the tanks, I can't claim they are spotless , they do appear to run clean when flushed out.