black water capacity in 17b

[yardsale]

In thinking about cold wheather dumping, I just calculated it would requrie about 4.5 gallions of antifreeze to fill up the 3" diameter pipe connecting the black water tank to the dump valve. My question is does the 20 gallion capacity quoted by Escape as the capacity of the black water tank include this volume, or is the total volume of tank and pipe about 24.5 gallons? I have been dumping a single gallon into the tank before use, clearly not enough.
Thanks.

[Brian B-P]

This is just a guess, but the advertised capacity is probably just the size of the tank as described by the tank manufacturer.

[rbryan4]

That's right. Its sold as a 20 gallon tank. That doesn't include the capacity of the outlet pipe to the gate.