Which tank

[D.Bones]

I have a 2017 big country which tank does the shower dump in Grey 1 or Grey 2 ,and is there a way I can back flush the line

 

[travelin2]

We have a ‘17 Bighorn with one bathroom so this should be the same for the BC as they are made on the same production line
#1 is for the shower and vanity
#2 is for the kitchen sink only

The only way to back flush the grey tanks is via an external flush adapter and valves

https://www.amazon.com/Valterra-T58-Twist-On-Waste-Valve/dp/B000BGHYJS/ref=mp_s_a_1_2_sspa?crid=2VR39SDGML8GH&keywords=valterra+3+inch+waste+valve&qid=1683969797&sprefix=valt%2Caps%2C98&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFXS1ZXSTJRMERSTFMmZW5jcnlwdGVkSWQ9QTA2MjkwMDkxMFRKSkU0Qk0yM0RaJmVuY3J5cHRlZEFkSWQ9QTAxMDYwODkzSDZUMTBJMU1HUTMmd2lkZ2V0TmFtZT1zcF9waG9uZV9zZWFyY2hfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

https://www.amazon.com/Valterra-F02-4100-Hydroflush-Removable-Anti-siphon/dp/B0002UHVAA/ref=mp_s_a_1_19?crid=2DK5PFMT8WGUN&keywords=rv+sewer+attachments&qid=1683969887&sr=8-19

 

[david-steph2018]

A good way to identify which tank goes to what drain, is to use food coloring. Pick up 4-5 different food colors, mix in a 5 gal. bucket. Then empty the bucket into 1 drain, mix another color, and do the same. HINT: write down what color you dumped into which drain.
When you dump, watch and see what color comes out.