The grey water and black water normally have black color tanks if they are still original.
You mentioned a black cover around the black tank, h'mm pics of this cover can help. Some prior owners may have added something. Post a pic of the cover. If you need help posting pics, let us know. We will help with that too.
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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