Two grey tanks - 40FLFS. How are they plumbed (i.e. what goes to what tank?)

[bullpup597]

We just bought a very nice 2018 Elkridge 40FLFS. It has two grey tanks and I assumed (wrongly) that when one fills up, the second tank is used.
That is not the case.

Doing dishes the other night, the water started to back up into the sink. I went to drain both tanks, and only one had water in it to drain. Nothing came out of the other grey tanks.

Is it assigned to only the washer/dryer if installed?

 

[david-steph2018]

The easiest way to find out what goes to what tank is to use food coloring. Mix up about 5 gallons of a color and dump down the drain.
Then drain it, and you can see what tank, then do that with each drain. Use a different color for each drain.

Hint, write down the color and drain so you do not get it confused, happens.

 

[James Donovan]

In my experience with multiple gray tanks, one is dedicated to the kitchen and the other is for the shower and bathroom sink(s). The food coloring idea is a pretty solid way to find out though.

 

[centerline]

mine is plumbed with washer/dryer, shower and vanity sink on one tank, and the galley sink on the other tank.... be careful when washing clothes, as the shower can back up, fill the shower pan, and run over if not noticed in time.... luckily my wife uses laundry detergent that has a strong floral smell, and when we noticed the trailer smelling abnormally like a bouquet of flowers, we got to looking and seen the shower pan had 2 inches of wash water backed up in it....