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Old 01-19-2014, 07:32 PM   #1
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Ok dumb question about Black and Gray holding tanks

A question that keeps coming to my mind on black and gray holding tanks. When we winterize how much should be left in tanks or should we leave the tanks open. Should we have lots of anti-freeze in tanks against the knife valves or dry?

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Old 01-19-2014, 07:43 PM   #2
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It's best to drain and rinse the tanks for winterization. You can use a little silicone grease on the knife valves. I wouldn't leave them open, varmints and creepy crawlies would find it too accommodating. A cup or less of RV antifreeze in each drain is all you need to keep the traps from freezing. Don't forget to drain and flush the water heater tank, then put the plug loosely back in place.


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Old 01-20-2014, 07:53 AM   #3
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x2. Drain the tanks and then add a bit of RV antifreeze via the toilet and sink drains (they sinks and shower need to have antifreeze in their P-traps anyway). A quart or so of water in the tank will keep the valve seals moist and the antifreeze prevents freeze damage. If the coach isn't level, use enough water to make sure some flows into the tank drain line.
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Old 01-20-2014, 08:15 AM   #4
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related dumb question mi

Debate with wife needs be settled. Do you leave grey and black water valves open or closed when living in a motor home?by
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Old 01-20-2014, 08:24 AM   #5
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Black water valve should be CLOSED. Otherwise all the heavy "stuff" collects on the bottom. You need liquid to flush that out. If I'm going to be in one spot for a while, I leave the gray open until the day before I leave. That way I have some gray to flush after dumping the black.
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Old 01-20-2014, 08:42 AM   #6
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Since we are talking black and grey, why are they seperate? Seems like if they were together you would aluways have plenty of water for the solids.
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Old 01-20-2014, 08:51 AM   #7
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Holeinone, good question. Many coaches have a "Sani con" system. This allows you to equalize the black tank, after draining, using grey soapy water. After rinsing the black tank several times with grey water, the black is equalized leaving approximately a third of a tank of grey water in it. This helps keep valves and gaskets lubed as well as keeping the walls clean. We have used this system for over two years and thus eliminating any odors or chemical use. Check it out Thetford makes the macerator pump system!
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Old 01-20-2014, 11:33 AM   #8
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On some motorhomes, one of the bathroom sinks drains into the black tank. That's the way our 2002 Beaver Patriot was designed.
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Old 01-20-2014, 11:41 AM   #9
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My two cents - keep the gray water valve closed until it is almost full, dump and then close it again. A friend of mine had a sever problem with sewer flies, they left the gray valve open. I am not taking any chance on that happening to me.
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Old 01-20-2014, 12:59 PM   #10
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For my two cents, we always leave the gray water valve open. Showers, dishes, laundry will fill the tank quickly and then fill the shower and then over flow onto the MH Floor.
Don and Nancy
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Old 01-21-2014, 06:07 AM   #11
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After tanks are dumped I fill them up with a bit of clean water and dump them again. Close the valves and put the cap on. While winterizing whatever pink stuff ends up in the tanks stays there. I then drop in a deodorizer and I'm done.

When it's time to have fun again, I dump the tanks once again and use some of this stuff: THETFORD DRAIN VALVE LUBRICANT
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Old 01-21-2014, 10:06 AM   #12
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HoleinOne, One reason (and maybe the major reason) they are separate is as djbmsu mentioned, when the gray tank gets full it will overflow into the shower; much better to have shower and dishwater coming up in the shower than urine and poop!
Dan & Arlene
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Old 01-21-2014, 01:34 PM   #13
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another reason for having them separate is the way a lot of people hook to a sewer system. I am in the campground I am in now for 5 months. We keep the grey tank valve open to allow liquids to constantly drain. As the earlier poster said that tank fills up pretty quickly from washing dishes, showers, etc. There are a lot of posts regarding the problems that arise with leaving the black tank valve open. By having two tanks you can leave the grey tank valve open when long term camping and just drain the black tank when you need to. Which for the two of us is once every week or two depending no how cold it is outside.
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Old 01-21-2014, 04:16 PM   #14
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Plus with only one tank you couldn't rinse the stinky slinky with grey water after dumping the black stuff.

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