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Old 06-02-2023, 10:32 AM   #1
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Exclamation Why do RVs have 2 Gray Water Tanks & Not 1!

Okay, so with our Outlaw motorhome, we are always filling up one of our two grey tanks. It's the one connected to our shower, so we end up dumping far more often. We have been considering moving to a fifth wheel and have found that will all the manufacturers have two gray tanks. WHY?

We wanted to plum our RV's two grey tanks together ourselves to equalize the two grey tanks. The problem is the frame and spacing don't allow it to function properly without some big drawbacks from what we could do ourselves. We did take it to our dealer, and then an independent shop and the cost was far too high to modify the chassis to accommodate the upgrade. One issue was the pipes would run too low for road travel. It seems to us that if you can do the plumbing, there could be a small pump and sensor system that could do this work. Has anyone seen anything like this on the market?

We are considering moving to a fifth wheel toy hauler in the next year or so and have been looking at the new Brinkley brand, and they have a true capacity. Why are not all fifth wheel brands doing this? Do they have a patent on it?



BTW, If you haven't heard of Brinkley RV before, we are extremely impressed with the new Brinkley Fifth Wheels. We've been looking at Alliance Valor, Grand Design Momentum, and now the Brinkley Model G Toy Hauler. We did a few factory tours while we were in Elkhart County, having our motorhome serviced; two words about the Brinkley brand... WELL BUILT! We've seen them and watched all the reviews and will no doubt buy the Brinkley toy hauler if we move to a fifth wheel.

Cheers from Sunny Barton Lake, Michigan.
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Old 06-02-2023, 10:42 AM   #2
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My 2007 5th wheel has a Grey and a Galley tank
I added another dump valve on the common drain header
with it closed I open grey/galley and combine them for increased 'grey' capacity

Design/layout/frame...all come into play when installing tanks...waste and fresh water
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Old 06-02-2023, 10:43 AM   #3
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If you have space you could simply “Y” the two outlets together with a common gate valve. As long as the individual valves are open and the common one is closed the water levels should equalize naturally I think.
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Old 06-03-2023, 09:01 PM   #4
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I believe that you answered your own question:

The problem is the frame and spacing don't allow it to function properly...

The cost was far too high to modify the chassis to accommodate the upgrade

One issue was the pipes would run too low for road travel.

RV manufacturers are known to take the cheap way out.

Tim
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Old 06-03-2023, 10:20 PM   #5
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my 5'r has 2 grey - one for shower other for kitchen
my wife can fill up shower one in 1 use
I've dumped were I was for grey water - just do it slowly if you're not hooked to sewer
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Old 06-04-2023, 12:02 AM   #6
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i guess in all the time of rving ive never even given it a consideration. i guess you want to prolong dump times? if you arent in a camp, i see no reason grey cant be dumped on the ground. the rural community i live in most household grey water goes to the river. if youre in a cg with hookups just dump more often.
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Old 06-04-2023, 03:19 AM   #7
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i guess in all the time of rving ive never even given it a consideration. i guess you want to prolong dump times? if you arent in a camp, i see no reason grey cant be dumped on the ground. the rural community i live in most household grey water goes to the river. if youre in a cg with hookups just dump more often.
Dumping on ground will be a very hot topic..

IMO shower/bath sink water is fine to garden house trickle in an area where ground absorption and evap can happen, granted many local laws forbid...
3 people using and portable outdoor shower is fine, Right.....

Kitchen water can be greasey..messey... and I say not a great idea...

as for the OP here, I have nor experience with 2 greys but I have friends that do,, no one really complains except for a friend with 5 kids...LOL
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Old 06-04-2023, 03:46 AM   #8
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Not all fifth wheels have two gray tanks. Both the 5-ers Iíve owned had one gray tank. It depends on the floor plan. If all the sources for gray water are close together, there will be a single tank. If not, you get two tanks. Generally, if you have two bathrooms or a rear kitchen, those are the layouts that end up with two gray tanks.

As to why the OEMs donít connect the two, you answered your own question, itís difficult and expensive. The units sell anyway, so they donít bother.
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Old 06-04-2023, 11:19 AM   #9
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We have 2 black and 2 grey tanks. The tanks are separated by about 20-25 feet. The shower/galley goes to tank one. The rear sink & washer hookup goes to tank 2. So, in this case it would not be practical to have the tanks connected.
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Old 06-04-2023, 11:24 AM   #10
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DUMP Grey water on ground......

Check State/Local Laws.....fines can be expensive

And if dumping...please use a sewer cap with hose connection....run hose AWAY from camp site.
Grey can STINK and who wants to have a puddle next to camp site
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Old 06-14-2023, 07:33 AM   #11
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DUMP Grey water on ground......

Check State/Local Laws.....fines can be expensive

And if dumping...please use a sewer cap with hose connection....run hose AWAY from camp site.
Grey can STINK and who wants to have a puddle next to camp site
We used to dry camp at ball games next to a great couple. She could tell you anything you wanted to know about MHs.
She would go ballistic if she saw anyone dumping grey water. She always said it was more dangerous to animals than black water.
I use a sewer cap with hose connection too. I once saw a guy take his cap off to dump not knowing his black water valve was leaking. He got more than a golden shower.
I have also added a final cutoff valve. I never had a problem with the old fiver or TT but the new one must have valves made in China!
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Old 06-14-2023, 07:57 AM   #12
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A couple reasons why some fifth wheels (and trailers) have 2 grey tanks.

First, the simple distance between the kitchen and the bathroom. To run the plumbing from one or the other, or both to one tank, is not possible because of the distance involved, requiring the pipe to have adequate "fall" and to pass over axles and frames. It's just logistically not possible.

So, you install your own cross over and the pipes are sloped downward. But now, you find yourself parked on a sloped campsite. How far off can the "level" of the camper be before nothing flows down that drain pipe?

Logistically, it's just not practical or feasible. Two tanks at opposite ends of the camper make better sense.


Second, Size of tank. Face it, there is only so much "space" between the frames of any camper. The frames themselves are only "so" thick. 8, 10, or 12 inch frames doesn't permit a very deep tank. That means, a larger tank need to be spread out over a larger area, but still fit that 8, 10, or 12 inch void to fit. That would make for a really long and/or really wide tank to accommodate both the kitchen and the bathroom.

It makes more practical sense to have 2 smaller tanks at each end of the camper.

We've had 2 different trailers (a travel trailer and now a fifth wheel) that had 2 grey tanks. Neither was an issue as far as which filled up first.

By trial and error, and by not being on full hook up sites, and by using my Barker Blue Tote, and by using a water meter to fill my fresh water tank, I determined we use much, much more water in the kitchen sink than the toilet and shower and bathroom sink combined.
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Old 06-14-2023, 03:34 PM   #13
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Originally Posted by PioanoMan View Post
Okay, so with our Outlaw motorhome, we are always filling up one of our two grey tanks. It's the one connected to our shower, so we end up dumping far more often. We have been considering moving to a fifth wheel and have found that will all the manufacturers have two gray tanks. WHY?

We wanted to plum our RV's two grey tanks together ourselves to equalize the two grey tanks. The problem is the frame and spacing don't allow it to function properly without some big drawbacks from what we could do ourselves. We did take it to our dealer, and then an independent shop and the cost was far too high to modify the chassis to accommodate the upgrade. One issue was the pipes would run too low for road travel. It seems to us that if you can do the plumbing, there could be a small pump and sensor system that could do this work. Has anyone seen anything like this on the market?

We are considering moving to a fifth wheel toy hauler in the next year or so and have been looking at the new Brinkley brand, and they have a true capacity. Why are not all fifth wheel brands doing this? Do they have a patent on it?



BTW, If you haven't heard of Brinkley RV before, we are extremely impressed with the new Brinkley Fifth Wheels. We've been looking at Alliance Valor, Grand Design Momentum, and now the Brinkley Model G Toy Hauler. We did a few factory tours while we were in Elkhart County, having our motorhome serviced; two words about the Brinkley brand... WELL BUILT! We've seen them and watched all the reviews and will no doubt buy the Brinkley toy hauler if we move to a fifth wheel.

Cheers from Sunny Barton Lake, Michigan.
There's a guy on the KZ Family Forum who did exactly this with his KZ fifth wheel. He had 2 dump valves and got tired of having to move his rig to dump the rear tank. Here's a link to the thread: https://kzfamilyforum.com/thread/1920/rear-kitchen-mod.

Lyle
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Old 06-14-2023, 10:31 PM   #14
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I have a Vanleigh and they have two grays equalized as one 90gallon.
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