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Open Roads Forum  >  Travel Trailers  >  Modifications and Accessories

 > Connection grey to black tank

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vtraudt

Brighton, MI

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Posted: 08/25/21 05:46am Link  |  Quote  |  Print  |  Notify Moderator

As in our Class C, our habbits/use of grey and black water capacity always creates the problem that the grey tank is FULL quickly, and the black is almost empty.

Over the years I always thought but never further looked into the possibility of an 'overflow' where the grey tank can overflow into the black tank to make use of this wasted capacity.

I assumbe both tanks (Forest River travel trailer) are rectangular and fairly close together.

I also assume that all grey water 'feeders' (shower, toilet sink, kitchen sink) have traps (smell), so no additional trap is needed between the 2 tanks?

Aside from plumbing issues (adding to connections to the top of both tanks, finding space, etc), any other things to consider?

JRscooby

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Posted: 08/25/21 06:46am Link  |  Quote  |  Print  |  Notify Moderator

1 of the Mods Dad had me do to his 5th wheel was put a drain point at about the 3/4 level of the grey tank. Had 2 valves; Open 1, would drain into stinky slinky, the other thru a hose bib to fill a container, into the sewer with a small hose, or where allowed, to water bushes.
FHU site, drain top of grey until black full, still plenty to chase the black. When he had to haul all water, do dishes in pan, and dump in toilet. (Can flush with dirty water)

As for connecting the tanks. Once you do that you have no grey water, it is all black, unless the black can't back into the other tank. And that connecter will be a good place for blockage, hard to clean, and real stink to grow.

valhalla360

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Posted: 08/25/21 07:05am Link  |  Quote  |  Print  |  Notify Moderator

JRscooby wrote:

As for connecting the tanks. Once you do that you have no grey water, it is all black, unless the black can't back into the other tank. And that connecter will be a good place for blockage, hard to clean, and real stink to grow.


Who cares if it's legally black water?

Gray water often smells worse, so no real stink concern.

Assuming everything drains to a single point, a simple and cheap solution is to buy a temporary twist on valve.

https://www.amazon.com/Valterra-T58-Twist-On-Waste-Valve/dp/B000BGHYJS/ref=asc_df_B000BGHYJS?tag=bingshoppinga-20&linkCode=df0&hvadid=80401840125241&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4584001431142158&psc=1

Attach the temporary drain valve and leave closed.
- After the gray gets full, open the gray valve.
- Then open the black valve
- (again keeping the temporary valve closed)
- The greater amount of water in the gray tank will flow down and then back up into the black tank.
- When you do get around to dumping, close all the valves, attach the hose to the temporary valve, then open the black followed by the temporary valve...once empty open the gray valve.


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vtraudt

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Posted: 08/25/21 07:57am Link  |  Quote  |  Print  |  Notify Moderator

Yes, I now see what you say: the grey and black MERGE ("T") already at the drain hose.

Just modify to make a "Y" with 3 valves (grey, black, main drain) or 2 (main/black (3.25 I think in my case) and grey (much smaller, maybe 2").

Normal operation: all closed.

Move grey to black: keep main/drain closed, open grey. If grey level is higher, will push into (fill) black.

Empty: open all.

2112

Texas

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Posted: 08/25/21 08:17am Link  |  Quote  |  Print  |  Notify Moderator

I do it as Valhalla360 outlined. I usually wait until I hear my shower burping before I open the gray.

We also use a plastic tub in the sink when washing dishes and pour that soapy water into the toilet. In my mind it helps prevent the dreaded pyramid and keeps the black tank clean. Does it actually work? I have no idea.


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jdc1

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Posted: 08/25/21 09:59am Link  |  Quote  |  Print  |  Notify Moderator

A Valtera Flush King 45 Degree Reverse Flush Valve Attachment would be what you want to use....like Valhalla 360 says. Close the adapter. Open grey. Open black. Close grey and black when they level out. Now your 40 gallon grey is 60+- gallons

ktmrfs

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Posted: 08/25/21 01:00pm Link  |  Quote  |  Print  |  Notify Moderator

vtraudt wrote:

Yes, I now see what you say: the grey and black MERGE ("T") already at the drain hose.

Just modify to make a "Y" with 3 valves (grey, black, main drain) or 2 (main/black (3.25 I think in my case) and grey (much smaller, maybe 2").

Normal operation: all closed.

Move grey to black: keep main/drain closed, open grey. If grey level is higher, will push into (fill) black.

Empty: open all.


exactly. And in our trailer we have a 36 gallon grey tank for the bathroom and a 36 gallon grey water for the galley. do the same thing if one grey gets full to equalize between the two grey tanks.

BTW when dumping, this also makes a quick and easy way to backflush the black tank. Empty the black, close main outlet, open grey and let it backfill into the empty black, close it, then drain the black again. repeat as appropriate.


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shum02

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Posted: 08/25/21 01:09pm Link  |  Quote  |  Print  |  Notify Moderator

2112 wrote:



We also use a plastic tub in the sink when washing dishes and pour that soapy water into the toilet. In my mind it helps prevent the dreaded pyramid and keeps the black tank clean. Does it actually work? I have no idea.


We do the exact same thing and I do believe it works great. I've never had issue with the black tank and the dreaded pyramid of poo.


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vtraudt

Brighton, MI

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Posted: 08/25/21 02:49pm Link  |  Quote  |  Print  |  Notify Moderator

That (tub in sink) is one way, certainly. Just trying to come with one more along the 'work smarter, not harder'.
Its desease (engineer), can't help it.

2112

Texas

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Posted: 08/25/21 04:47pm Link  |  Quote  |  Print  |  Notify Moderator

vtraudt wrote:

That (tub in sink) is one way, certainly. Just trying to come with one more along the 'work smarter, not harder'.
Its desease (engineer), can't help it.
The idea is to get a strong, hard flush of water straight down into the black tank to bust up what may have stuck to the bottom. Would you rather stick your arm or a broom handle down there to bust it up?

I understand your disease very well. Retired EE, master tinkerer here.

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