Black and Gray water holding tanks

[Michael M]

I have a 2017 Momentum 399TH. Specs for the RV state I have 1 black water tank and 1 gray water tank yet I have 2 release valves for each. Each valve also seems to release its own reservoir of water. There is a bathroom in the front of the RV and one in the toy hauler part in the back. There is a valve associated with each bathroom. If there is only one tank, why would I need 2 valves and why do they each seem to drain a separate supply of black/gray water? I hope this makes sense and I appreciate any feedback.

Michael M

[FT4NOW]

I also have a 2017 399. I've dropped the underbelly so I can confirm the following. The 3 dump handles in the connection compartment are for 2 grays and a black tank. Black for the toilet, 1 gray for shower/sink and 1 gray for kitchen sink. The 2nd black handle behind the rear axle is for a black tank which is for the garage toilet, sink and washer water outlet pipe. There are 2 black tanks, 2 gray tanks, 2 fuel tanks, 1 fw tank unless you got the aux FW tank option.

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[huntr70]

Where did you see those specs? The 399 has always had 2 gray and 2 black tanks.

They don't break out how many tanks in their specs, just total capacity.

[Michael M]

Likely a large assumption on my part (I know the risk of assuming), but when I google how many black tanks the 399TH has, the answer given is 1. The brochure does state total black water capacity and does not state how many tanks, but dealer information online regularly lists one black tank. Also, there is only 1 black tank sensor on the myRV computer screen. Is that just measuring the front bathroom tank, back bathroom tank or somehow both tanks? I appreciate everyone's responses.

Michael

[FT4NOW]

Likely a large assumption on my part (I know the risk of assuming), but when I google how many black tanks the 399TH has, the answer given is 1. The brochure does state total black water capacity and does not state how many tanks, but dealer information online regularly lists one black tank. Also, there is only 1 black tank sensor on the myRV computer screen. Is that just measuring the front bathroom tank, back bathroom tank or somehow both tanks? I appreciate everyone's responses.

Michael

You should have 2 black sensors on your MyRV screen. It's possible it wasn't programmed correctly. You can look online at LCI for the programming manual and try to add it yourself. Also behind the false wall in the basement is where the level indicator module is, you can look at it and see how many sets of tank wires are hooked up to it. I have sensors for all my tanks except for the fuel tanks on the MyRV display.

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[Michael M]

That is great to know. Thank you very much!