Ran into the same issue on my new(er)-to-me trailer and got a quick lesson from the lead tech at Jackson Center.
For the travel trailers, the fresh water drain almost all of the time is on the same side as the fresh water fill. So, if the fresh water fill is on the street side, the drain valve (if it still exists and was not yanked off or removed) is most likely somewhere in the wheel well on the street side. Actual location of the drain valve within the wheel well (forward, between, aft) does seem variable.
Originally Posted by eldin
My owner's manual for 25" Excella shows 2 drain plugs underneath slide out pantry. Pantry only slides out half way and is completely enclosed. Any idea how to get that slide out pantry OUT to get to the two plugs? If you can help .. could you please reply by email: Marti2Ray@vnet.net
This seems like it is referring to draining the interior water lines versus the holding tank valve (per the OP's question). And yes, they are in many different locations. While far from an expert in this area, I have observed that the interior line drains do poke out of the belly, so take a look at the underside for a pair of tubes a few inches apart, and the valves are directly above. In terms of accessing the valves from inside the rig, chances are good they are easily accessible (presuming good personal flexibility) through a hatch / door once you know where they are.