I am trying to replace the valves inside the toilet tank. I have done this before and always seem to have a problem. This time I cannot remove the two plastic nuts under the tank, holding the metal intake tube to the tank and the valve.

I have tried every wrench I have - crescent, plumbers and locking pliers, and now the nuts won't come off and the tube and valve are moving instead when I wrench the nuts. (I did first try by hand, but the nuts were tight.)

Loosening the nut at the bottom of the intake tube by the water cutoff valve did not help. I tried to tighten it back up, but now the tube is offline from the water valve assembly.

I tried the oil used to release sticky things like this, but it did not help any.

Tried using two wrenches - to hold the old valve while trying to take the old nuts off, but it did not help.

Tried both clockwise and counter-clockwise, too.

The instructions in the fluidmaster kit and those on the Internet are clear, but these two nuts just do not want to come loose and I am at my wits end in thinking of ways to get them loose so I can lift the valve out and put a new one in the tank.

I would like a detailed answer, if anyone had it. Thanks ahead of time !