320G Waste Tank Question

[Brucedeuce]

We recently purchased a 320G and took our first trip in it over the 4th of July weekend (total of 4 days). My question has to do with the number of gray and black tanks and the capacity of each. Is anyone familiar with this? Our panel has lights for Gray 1, Black 1, Gray 2, Black 2 which led us to believe we had 4 tanks total. We were unable to find a pull valve for a second gray tank, however. We've been told that the back gray and black tank might be combined. Specs say 78 gal gray water total and 78 gal black water total, but if there are 3 tanks (gray 1, black 1 and gray/black 2 combined) how are they divided? Meaning, what is the capacity for each tank. Our gray 1 read full in just 2 days and that was only washing dishes and 3 short showers. We never even used the back bathroom.

[CoChris]

We recently purchased a 320G and took our first trip in it over the 4th of July weekend (total of 4 days). My question has to do with the number of gray and black tanks and the capacity of each. Is anyone familiar with this? Our panel has lights for Gray 1, Black 1, Gray 2, Black 2 which led us to believe we had 4 tanks total. We were unable to find a pull valve for a second gray tank, however. We've been told that the back gray and black tank might be combined. Specs say 78 gal gray water total and 78 gal black water total, but if there are 3 tanks (gray 1, black 1 and gray/black 2 combined) how are they divided? Meaning, what is the capacity for each tank. Our gray 1 read full in just 2 days and that was only washing dishes and 3 short showers. We never even used the back bathroom.

First, welcome to the forums. Lots of great people here and hopefully someone with your model and more specific knowledge will give you more specific answers to your questions. To partially address your questions;

1) The monitors used int he panels are somewhat generic and used across multiple model lines. Just because it has Back 1 & 2 and Gray 1 & 2 does not mean you have 4 tanks. Our Solitude 310GK has all four monitor buttons/lights, but only has three tanks (single bath - no black 2).

2) Looking at your Momemtum 320G, with the second 1/2 bath I would guess (typically) you have a a combine black/gray tank (toilet & sink waste) for that bathroom. So you would have two black tanks (front bath toilet and combine rear bath) and probably two gray tanks (from bath sink & shower and one for kitchen sink). My guess is they are all four the same size so ~39 gallons each. You can always call Grand Design customer service with your model and VIN and they can tell you exactly what you have in your trailer. It does vary from model to model and date of build.

3) Have you checked behind the street side rear tire for a sewer/dump connection and a black (or gray) handle? If they are there, this would be for the rear black tank. Some floor plans (especially with four tanks) have an outlet and dump handle under the trailer separate from the docking station.

4) The indicator light (empty, 1/3, 2/3, full) are notoriously inaccurate and they will become "suck" at different levels over time. Most people just learn how long they can go before having to dump a specific tank. Use the search function (upper right of each page) as there are a lot of discussions on this very topic.


Hope that helps get you started and someone with more knowledge can chime in.

Again, welcome and enjoy your new trailer.

Chris

[DarylB]

The 3 waste tanks are all 52 gal each. Because the rear waste tank is actually grey & black combined (52 gal), they divide it by 2 and add the 26 gallons of each to the front tank capacity’s and call it 78 for grey and 78 for black on the specs.

[Brucedeuce]

Hi Chris,

Thank you for the reply. This is all good info to have for future reference. My husband crawled all over underneath the rig to try to find a second gray release valve and couldn't find it. We did attempt to contact GD, but they were slow in getting back to us. They kept telling us they would email some schematics, but never did. I will read up on the indicator lights. I'm so glad I found this forum. I have a feeling I will be referencing it often. Thank you again!

Kim

[Brucedeuce]

Thank you for responding. This makes sense. We'll have to make some appropriate adjustments when we're dry camping. This helps a lot!

Thanks again!

Kim

[MooManChu]

FWIW,

Thanks for the post to everyone here. I can stop scratching my head now...We recently took the inlaws camping (in our new 320G) and they stayed in the garage "suite". For the life of me, I couldn't figure out how the heck the black tank filled up in less than a week (insert inlaw joke here).