NFPA 1192, Standard on Recreational Vehicles, 2008 Edition states:
7.5.4 Connections Between Holding Tanks. No drain connection shall be made between liquid waste and body waste holding tanks upstream of any fullway temination valves.
I just pass this along so you can have all the facts.
NFPA 1192 is not the law, just the industry standard that professionals use.
There is nothing wrong with taking gray water and dumping or pumping it into the back holding tank, just don’t hook them up.
Has anyone let the gray tank get too full and then find themselves standing in gray water. I don't really want to see my toes in gray/black water.
As long as you make sure not to overflow your grey tank, there is no reason not to allow the grey and black to mix by opening both valves with the termination cap installed. Many rigs have a bathroom sink that connects to the black tank instead of the grey.
I have one of those cheater type termination caps with a hose fitting on it. If also have a garden hose type shutoff ball valve. If I ever need to mix, I'll out the valve on the termination cap and then open both gate valves. The ball valve can be used when dumping to cleanly drain off the small volume of liquid between the termination cap and the gate valves.
Nobody I've know ever planned to overflow a tank. But gauges and guesswork don't always win, and it happens. I've had grey back up into my tub, and it ain't pretty.
If it were potentially mixed with black? Oh, my...
I like the transfer pump idea. It should prevent cross contamination better than a backflow valve (which can fail).
I guess I'm spoiled by always having enough room under the coach to add a second tank, but I still think mixing via the drain pipes is just asking for a Robin Williams moment. Gate valves are installed at the tank outlet for a reason. Pipes break. Especially the low hanging ones when they accidentally hit something...
2005 Winnebago "Minnie" 31C (was a three-time Jayco owner)
kenmol wrote: I installed an extra valve at the end of my 3"pipe. I keep the last valve closed and open the gray and black valves. The tanks will balance themselfs and when it is time to dump I just hook up the hose and pull the third valve open.
I LIKE IT! that adds capacity to either tank, with no need for a pump.
2006 Open Road 316 RLDS-5
2004 F-250 Diesel, short bed, SRW, Crew cab, 3.73 auto.
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