Is it possible to install bigger grey water tanks?

[Tony Ramage]

I have a 2022 Momentum 351 MS and they say it has 78 gallon capacity for grey water. But on our first trip we filled the main grey on the first day. So I called Grand Design Customer Service and they said it’s actually split between the half bath and the main area. So I only get 39 gallons for the main and 39 gallons for the half bath which hardly gets used. I am wondering if anyone knows if it’s possible to have a bigger grey tank added? Or if it’s even worth the hassle?
Thanks!

- Tony

[Second Chance]

One thing a lot of us do is install a Valterra gate valve at the sewer outlet, close the black tank, close the Valterra valve, and leave both gray tanks open. This effectively couples the two gray tanks together.

Rob

[Tony Ramage]

One thing a lot of us do is install a Valterra gate valve at the sewer outlet, close the black tank, close the Valterra valve, and leave both gray tanks open. This effectively couples the two gray tanks together.

Rob

Oh ok, thank you. I’ll look into that. I’ve never heard of a Valterra valve. Is it easy to install on your own?

[RickLight]

My underbelly has room for slightly larger tanks of all types. However weight balance and frame strength issues make me very cautious. The benefits of another 10-15 gallons has me looking at 'blue boys' for 20-35 gallons instead.

[Hoopy Frood]

Oh ok, thank you. I’ll look into that. I’ve never heard of a Valterra valve. Is it easy to install on your own?

Not hard, but it, as usual, depends on the application. I put this one, https://www.valterra.com/product/twi...e-valve-boxed/, on the end of my black tank drain because the OEM valve never seemed to shut off completely. I had the clear elbow, but that only shows you what's there, not how to deal with it.

Check around for prices, I bought mine off Ebay for $8, most places are around $14.

[Tony Ramage]

Not hard, but it, as usual, depends on the application. I put this one, https://www.valterra.com/product/twi...e-valve-boxed/, on the end of my black tank drain because the OEM valve never seemed to shut off completely. I had the clear elbow, but that only shows you what's there, not how to deal with it.

Check around for prices, I bought mine off Ebay for $8, most places are around $14.

Oh ok, I’ve seen those. I’ve just never known the name I guess. Lol. Thanks for the info.

[alkbch]

One thing a lot of us do is install a Valterra gate valve at the sewer outlet, close the black tank, close the Valterra valve, and leave both gray tanks open. This effectively couples the two gray tanks together.

Rob

Unfortunately that doesn't work with several models because the front grey tank (kitchen / front bathroom) is far away from the rear combo grey/black tank (half bath / laundry)

[huntindog]

I have a 2022 Momentum 351 MS and they say it has 78 gallon capacity for grey water. But on our first trip we filled the main grey on the first day. So I called Grand Design Customer Service and they said it’s actually split between the half bath and the main area. So I only get 39 gallons for the main and 39 gallons for the half bath which hardly gets used. I am wondering if anyone knows if it’s possible to have a bigger grey tank added? Or if it’s even worth the hassle?
Thanks!

- Tony

How many waste tanks do you have? IOW how many handles do you need to pull to dump all grey and black?
I am trying to figure out from looking at your floorplan just how it is plumbed.

[Tony Ramage]

How many waste tanks do you have? IOW how many handles do you need to pull to dump all grey and black?
I am trying to figure out from looking at your floorplan just how it is plumbed.

There’s two black tanks and two grey tanks. But there’s two black handles and only one grey handle. So I’m not sure how it’s plumbed.

[alkbch]

There’s two black tanks and two grey tanks. But there’s two black handles and only one grey handle. So I’m not sure how it’s plumbed.

That’s incorrect. There’s only three tanks.

One grey tank for the shower, the bathroom sink and kitchen sink.
One black tank for the front toilet near the shower.
One combo grey/black for the rear half bath (if option selected) and washer dryer hookups.