The knife valve is the part that opens when you pull the drain handle. It's like a flat paddle that slides in/out of the round pipe and opens or closes. It's at the end of the pipe that empties the tank, in my case the grey water tank.
Because I didn't fully drain all water from the grey tank, once I closed the valve ( pushed in the handle ), some water built up behind it in the drain pipe, and froze, splitting the junction.
What I didn't do properly:
Drain both grey and black tanks..... Completely ( they can slow trickle for a long time )
pour RV antifreeze down both sink and toilet, to feed both grey and black tanks. the antifreeze will flow through the tank and down the drain pipe. Slightly open the knife valve and you should see the pink antifreeze begin to drain.
Close it up.
Jim & Kim from Colorado
2014 Eagle 30.5 RLS
2015 Dodge 3500HD SRW 6.7L
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