Equalizing grey tanks?

[evanhix]

I have a 2017 Carbon 357 with 2 grey tanks. I assume that 1 serves the garage bathroom & w/d drain and the other serves the front master bath and kitchen sink. Both tanks have seperate valves but drain to the same outlet. I installed a valve at the main outlet because I got tired of the surprise liquid that spurts out when I remove the cap. My question is, could I leave both grey valves open and let the tanks equalize therefore increasing the capacity of the most used front tank? I had a Prevost driver tell me that he does this on his rig. Is it safe on toyhaulers or not recommended? Thanks for any info.

[chuckster57]

I suppose it would work. Until MY 2018! Imagine by Grand design had 2 grays with one valve.

[JRTJH]

Yes, it will work to equalize the two tanks. We do that when dry camping quite often. Since we use paper plates (they make good fire starters after eating) we don't have a lot of gray water dumped into the galley tank. So, we also have a terminal valve slide that we leave closed and I open both gray tank dump valves. That allows gray water from the bathroom tank to flow to the galley tank extending our stay (before the tanks are full) by a couple of days.

It sounds like Grand Designs plumbed the Imagine gray tanks "behind a single valve" so they will always equalize. Every time I have to crawl under the slide to pull the galley valve, I wonder why there's even a dump valve back there. It would have been so much easier to just have installed the front gray valve in the "T" rather than behind it. That would have eliminated the need for a valve under the slide.

[chuckster57]

And they added a second gray valve this year. Still one termination point.

[66joej]

Originally Posted by evanhix

I have a 2017 Carbon 357 with 2 grey tanks. I assume that 1 serves the garage bathroom & w/d drain and the other serves the front master bath and kitchen sink. Both tanks have seperate valves but drain to the same outlet. I installed a valve at the main outlet because I got tired of the surprise liquid that spurts out when I remove the cap. My question is, could I leave both grey valves open and let the tanks equalize therefore increasing the capacity of the most used front tank? I had a Prevost driver tell me that he does this on his rig. Is it safe on toyhaulers or not recommended? Thanks for any info.

I installed one of those quick connect valves at the black/grey tank outlet drain. Have always left both grey tanks open since doing this.

[evanhix]

Any idea why they would design the tanks this way? Why not have one large tank that is shared be all grey water drains? Or plumb both together so that they can be shared?

[JRTJH]

Originally Posted by evanhix

Any idea why they would design the tanks this way? Why not have one large tank that is shared be all grey water drains? Or plumb both together so that they can be shared?

Probably "engineering specifications" like distributing the weight load, space limitations like where would you put a 80 gallon tank vs placement of two smaller tanks (in available spaces), cold weather applications like maintaining a "drain slope" inside the "conditioned spaces" of the floor while preventing exposed plumbing from becoming "frozen pipes".

If you think about it from a practical application, having two tanks in different locations in the floor, you can distribute the weight and not affect "balance". Having one large tank (in the front or in the back) would have a significant impact on tongue weight or pin weight. There's only so much space "over the axles", and not all the tanks can go there. On most trailers with two tanks, one is forward of the axles and one is behind them.

It's all about "carrying weight" without unbalancing the load.... I know, not an easy concept to master, and Keystone hasn't completely "mastered the concept" in all of their trailers, but in most, tongue weight remains a fairly constant percentage of total weight throughout the weight range from empty weight to maximum GVW. They do it by placement of available storage locations within the trailer and available tank storage for liquids.

[Sandfreak]

Originally Posted by evanhix

I have a 2017 Carbon 357 with 2 grey tanks. I assume that 1 serves the garage bathroom & w/d drain and the other serves the front master bath and kitchen sink. Both tanks have seperate valves but drain to the same outlet. I installed a valve at the main outlet because I got tired of the surprise liquid that spurts out when I remove the cap. My question is, could I leave both grey valves open and let the tanks equalize therefore increasing the capacity of the most used front tank? I had a Prevost driver tell me that he does this on his rig. Is it safe on toyhaulers or not recommended? Thanks for any info.

How hard was it to add the valve also could you post a pic?

[JRTJH]

sandfreak,

There is no actual "installation" involved. The valve that is being discussed is an aftermarket "twist-on" valve by Valterra (there are other companies that make similar valves). You simply remove your "end cap" (where you attach the dump hose), twist the valve onto the 4 barbs, then reinstall your "end cap" on the outer side of the new valve. It operates just like your existing valves, pull to open, push to close. That will allow your gray water to flow from the full tank to the "normal outlet" but instead of flowing into the dump hose, it flows "upstream" (via the drain line) and equalizes the volume between the two tanks.

Adding the valve to your terminal connector serves an even more "refreshing" advantage. It prevents the "gush of goo (or poo)" that can happen if you have a leaking dump valve on a tank. Once you ever experience the "surprise behind the cap" you'll know just why Valterra sells so many of these "little lifesavers"......

Here's a picture of the valve. It's available for about $20 at most RV parts stores, online at any RV parts outlet as well as Amazon, EBay and other sources.

[Sandfreak]

Originally Posted by JRTJH

sandfreak,

There is no actual "installation" involved. The valve that is being discussed is an aftermarket "twist-on" valve by Valterra (there are other companies that make similar valves). You simply remove your "end cap" (where you attach the dump hose), twist the valve onto the 4 barbs, then reinstall your "end cap" on the outer side of the new valve. It operates just like your existing valves, pull to open, push to close. That will allow your gray water to flow from the full tank to the "normal outlet" but instead of flowing into the dump hose, it flows "upstream" (via the drain line) and equalizes the volume between the two tanks.

Adding the valve to your terminal connector serves an even more "refreshing" advantage. It prevents the "gush of goo (or poo)" that can happen if you have a leaking dump valve on a tank. Once you ever experience the "surprise behind the cap" you'll know just why Valterra sells so many of these "little lifesavers"......

Here's a picture of the valve. It's available for about $20 at most RV parts stores, online at any RV parts outlet as well as Amazon, EBay and other sources.

Thank you...

[evanhix]

Originally Posted by Sandfreak

How hard was it to add the valve also could you post a pic?

This is the permanent valve that I installed from amazon. I previously used the quick connect bayonet style but it hung down to low and I was afraid of clearance. Otherwise it worked well. Permanent install was simple. Hacksawed the old valve off and pvc glued the new valve on. Took about 10 minutes.

[Outback 325BH]

I would love to do that, however my plumbing won't allow for it. I have three tanks: one black and two gray... with two discharges: one servicing the black and one gray, the other servicing the second gray.

No biggy though.


Sent from my iPhone using Tapatalk

[mikz86ta]

Originally Posted by evanhix

I have a 2017 Carbon 357 with 2 grey tanks. I assume that 1 serves the garage bathroom & w/d drain and the other serves the front master bath and kitchen sink. Both tanks have seperate valves but drain to the same outlet. I installed a valve at the main outlet because I got tired of the surprise liquid that spurts out when I remove the cap. My question is, could I leave both grey valves open and let the tanks equalize therefore increasing the capacity of the most used front tank? I had a Prevost driver tell me that he does this on his rig. Is it safe on toyhaulers or not recommended? Thanks for any info.

I wish they had a map of the system and a standard.
My rear black tank does rear toilet and washer. I know this because I seldom use rear toilet and have a washer I use alot. And it gets filled. Upon draining, the water is mostly clear with a slight tint of whatever color the detergent is. Lol

[jsmith948]

Originally Posted by evanhix

This is the permanent valve that I installed from amazon. I previously used the quick connect bayonet style but it hung down to low and I was afraid of clearance. Otherwise it worked well. Permanent install was simple. Hacksawed the old valve off and pvc glued the new valve on. Took about 10 minutes.

Hopefully you won't encounter any issues down the road - but - the sewer drain pipes are ABS plastic and I don't know if PVC glue will melt the ABS together correctly. Just sayin'

[Dave W]

Originally Posted by jsmith948

Hopefully you won't encounter any issues down the road - but - the sewer drain pipes are ABS plastic and I don't know if PVC glue will melt the ABS together correctly. Just sayin'

The two types of plastics will bond with the right 'glue', called transition cement and is Oatey Transition Cement 30925. Anything else - probably wont last with any pressure

[GovGeek]

Originally Posted by Outback 325BH

I would love to do that, however my plumbing won't allow for it. I have three tanks: one black and two gray... with two discharges: one servicing the black and one gray, the other servicing the second gray.

No biggy though.


Sent from my iPhone using Tapatalk

I have the same configuration in our 324CG, and the galley grey tank is forward with the cleanout under the slide. I'm trying to figure out a way to delete it and move it near the aft cleanout area.