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Old 02-10-2012, 08:36 AM   #15
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I Leave it closed until its near full or after the Black water has been dumped. I just cleaned out the trap in a shower in my home and was suprised at the amount of sludge coating the inside of the pipe. That was likely from soap and shampoo. I like the idea of adding a cup of water softner and filling the sinks with hot water once a year. I've heard folks do the same for their black water tank as well

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Old 02-10-2012, 08:46 AM   #16
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I see ads for waste tank treatments that show a very stinky rig, I can guarantee you one thing. That idiot has his valves open.

#1 cause of waste tank odor is not the tank, nor it's contents, it's the open dump valve. Close the valve and the stink goes away.

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Old 02-10-2012, 08:59 AM   #17
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I alternate the grey tank valve each time I dump the black tank. I move about only four time a year so I don't get much sloshing action on the tanks. Luckily I have a rinse feature on the black tank but the grey tank needs that whoosh every so often to clean out grease and food particles that settles on the bottom of the tank. If those food particles dry they are harder to remove. When I do move I add about 10 gals. of water to each tank along with water softener and Dawn and I'm always surprised at the amount of black matter that comes from the grey tank the next time I dump. When you think about it, it's the same stuff in each tank but at a different stage of decay.
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Old 02-10-2012, 09:22 AM   #18
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We keep ours closed until full to minimize odors and to keep those little flying knat thingys that seem to hang out around dump connections from getting into our grey tank and possibly into the rig.
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Old 02-10-2012, 11:16 AM   #19
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Never an odor problem. No sludge pile either.

We have fantastic fans.

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Old 02-10-2012, 05:36 PM   #20
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Keep Both Valves Closed

Originally Posted by Hootie-Owl View Post
I have a question:

When staying for a week or more in a RV park with full hookup, do you all leave your grey tank dump valve open or closed?

I have been leaving it closed and dumping it when it fills up. Another person in the park told me to leave it open until I am getting close to dumping the black tank.

I tend to think that even the grey tank should get a good flush when dumped so I leave it closed all the time.

Any thoughts would be appreciated.
Leaving the black valve open is the source of many cute "brown tower" jokes; and, leaving the gray open is an outdated practice that causes many problems. Most manuals and authoritative publications nowadays instruct owners to leave both valves closed, until it is time to dump.

With little benefit, an open gray valve makes you vulnerable to a situation where a black water dump is needed, but there is no gray water to flush your hose. In addition to that, the threat of gas and insect ingress makes it a health issue.

Of course, if you can't descend the stairs of your coach once every two or three days, and don't mind the gas and bugs, an open gray valve is just the ticket.
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Old 02-10-2012, 05:45 PM   #21
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I guess by now you have figured out that it is personal preference.There is nothing in any manuals that address this other than go with the flow and keep both flowing
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Old 02-10-2012, 05:54 PM   #22
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a lot of if's in that question. how big is your holding tank, will it last you until you get ready to leave? don't worry about sewer smells, you have water in your pee traps so no smell should get into the TT or MH. I usually keep an eye on the tank to see what it's needs are. It is a good idea to flush a full tank as stated above as it does get food particles in with the soap. I like that idea so much I installed a quickie flush in the grey water tank to flush out any soap scum and food that gets in there. the quickie flush does such a great job of flushing down the walls it even keeps the sensors working much better and more accurate. depending on what time of day I get to camp, I might not even hook up my sewer hose for a couple of days. I just make sure the electricity and water are hooked up so the frig works and keep DW's beer cold.
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Old 02-10-2012, 05:58 PM   #23
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I keep both of mine closed until full. As stated, there are things that get into the gray tank as well that smell and can cause clogging. I prefer a really good 'whoosh' everytime I dump it. And also as stated, gnats have more opportunity to get in as well when it stays open.
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Old 02-11-2012, 10:55 AM   #24
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Grey Tank Odor

I Prefer to keep the valve closed unless DW is using the washing machine.

Several reasons:

Odor: Not necessarily from my tank, from the parks sewer. It's easy enough for sewer gas to 'bubble' up through the p-traps with not a whole lot of pressure. It's happened. If you haven't used the washing machine in a long time the p-trap might be dry anyway.

Woosh factor: When I drain the black tank I also drain the grey. The volume of the grey water creates a venturi effect that sucks waste out of the black tank.

Solid matter: It will not be cleared from the tank by a trickle. And once it sticks to the bottom.......

Leaks: If you leave the valve open the first indication of a leak could be a big puddle.

That's my opinion, and it's worth exactly what you paid for it.........
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Old 02-11-2012, 11:54 AM   #25
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Originally Posted by wa8yxm View Post

I see ads for waste tank treatments that show a very stinky rig, I can guarantee you one thing. That idiot has his valves open.

#1 cause of waste tank odor is not the tank, nor it's contents, it's the open dump valve. Close the valve and the stink goes away.
It's certainly nice to see that people have opinions. I'm not one that believes one size fits all in anything, and I think it goes double for motorhomes. Everyone needs to find a way that works for them and then use it.

We leave our gray tank open when at full hookups, black tank closed. On Saturday I'll close the gray tank whever it's convenient during the day. The DW does a load of clothes on Sunday morning. A routine she has which works well for us. After she's washed a load on Sunday I hook up the black tank flush hose and drain the black tank, flush it, and then dump the gray tank for whatever whoosh value it has.

The rest of the week the grey tank is free to drain as it pleases. If a load of clothes needs done, there's no need to check the tank to see if it'll fit. No need to empty a half full tank because running a load at night would require dumping before showers the next morning, etc.

We never stay longer than a month at any particular place which is where the above routine is in effect. Sometimes we move several days in a row between dumping. That certainly agitates the partial loads of water in each tank. I would be surprised that the buildup in my tank is any more of a problem that the person who always waits for a full tank to dump.

A lot of different methods have been suggested on this thread, if one doesn't work for you, try a different one.


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