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Old 08-13-2017, 06:39 PM   #1
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Black and Grey Tanks Open ? Closed?

New to a Class A gas with a gravity feed for grey and black tanks. My B+ had a macerator pump so when you dumped, you knew what was going on, as you had to do it.
I have had the impression that TT and A's and C's that have their hookups at campgrounds leave them open, so stuff drains as it happens.
Recently I read, it is not a good idea to leave the tanks open.

So which is it? what do you do? How does it work? Any recommendations?

Starting the learning curve over again after 8 years with one rig. Oh well!
Thanks in advance for any inputs.

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Old 08-13-2017, 06:42 PM   #2
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I keep both closed until I need to dump. Some keep the gray open. Never leave the black open. You will get a pyramid of poop that causes all kind of issues.

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Old 08-13-2017, 06:42 PM   #3
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Black and Grey Tanks Open ? Closed?

Leave the black closed till it is ready to dump.
Grey is optional but nice to have grey to help rinse after dumping black.

I typically leave both closed until needing to dump.
Only exception is if laundry is being done then grey is left open.
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Old 08-13-2017, 06:42 PM   #4
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Open or Closed?

Having spent 8 years with a B+ that had a macerator, I have been under the impression that gravity fed black and grey drains are left open when at a full hoop up site and drain as activity happens. But also just read a post that said that was not a good idea.

Just bought a Class A gas with gravity feed drains. So, do you leave the valves open or closed? What works best for you and why?

What should I know that I dont?

Appreciate the information ... learning all over again.
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Old 08-13-2017, 06:45 PM   #5
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Closed until ready to dump. Especially black to avoid water drain away and leaving solids to solidify. Some will leave grey open because if dishwasher and laundry creating lits of water. I do not as often there is no trap in the CG sewer connections so odors, bugs, etc. may come up your hose.
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Old 08-13-2017, 06:46 PM   #6
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Leave the black tank closed until it's at least 2/3 full. It needs water in it or you'll end up with dried sewer pickles in the bottom.
Some people leave the gray water valve open but I like to use that water to flush the hose after draining the black tank.
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Old 08-13-2017, 06:50 PM   #7
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Black closed except when dumping. Gray could be either way but probably better off closed.

The issue is RV plumbing does not have the slopes that house plumbing has to carry away the solid waste with the reduced flush water. The result is a more or less solid mass of solids building up in the black tank. Leaving the valve shut lets the water keep everything soupy. Using extra water also helps. Don't be stingy with flush water.

The gray tank is used to flush the hose after a black dump. If you start with it closed and get a feel for what it takes to fill it you might find you can do an extra dump or leave it open for a day or two. You are also playing with a smaller version of the dreaded pyramid of poo but with food particles. Getting the tank more than half full before a dump helps that. The exceptions is if you have a clothes washer. Leave it open when washing clothes.
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Old 08-13-2017, 06:51 PM   #8
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Both closed .
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Old 08-13-2017, 06:55 PM   #9
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Stop and think about it. Do you think that when the toilet is flushed, the solids will flow over a flat horizontal surface to the opposite side where is can exit the tank? Probably not. And as soon and the second and third flush solids get stopped by the first flush that may have dried, you have the makings of a real big problem that you will not enjoy correcting. For that reason, it is advised to start with 5 gallons of water in the black tank and keep the valve closed so that as solids accumulate in the tank, thay remain in suspension or at least not sticking to the bottom. Then when the tank is at least 2/3 full, you open the valve and all of the solids will flow out with the liquid. Then if you also kept the grey tank closed, you can flush the black water out of the hose with the grey water. This process keeps solids from building up in the black tank.
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Old 08-13-2017, 07:09 PM   #10
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I have 3 tanks....all stay closed until at least 2/3 to full. I drain black first, galley second, bath and shower last. I will start using geo method for black tank next trip
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Old 08-14-2017, 12:21 AM   #11
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Zeke, first of all, Welcome! You've come to the right place. Many happy miles!

There is only one hard protocol vis a vis tanks, and that is black closed and plenty of water.

Gray tank can stay open or closed, your choice. As many have stated, a gray quantity can be useful. If you drain it after you've drained your black, it will serve to rinse the residual black water out of your hose line.
But it may not be convenient. These systems are generally designed such that the gray and black quantities together approximately equal your fresh tank. We have 45 gal black and 65 gal gray, yet we find that it is the gray tank that is our limiting factor. The gray fills considerably quicker than the black, and I find myself going out too often to drain things. For that reason I leave our gray open until I estimate a day or two until black full, then close the gray. This gives me enough retained gray to rinse the hose line.
Good Luck with your A, and again, Welcome!
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Old 08-14-2017, 03:39 AM   #12
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All closed until dump.
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Old 08-14-2017, 04:26 AM   #13
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Open or Closed

I've always left the black tank drain closed until it reaches about 2/3rd's full and left the grey tank closed until it reaches about the same.
Reason being that when draining the black tank, you need the water from the grey tank to clean out the hose - otherwise you'll end up with "stuff" you don't want plugging up the hose. - Drain the black first - when done open the grey valve to clear out everything.
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Old 08-14-2017, 04:43 AM   #14
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All closed. Half the time I don't even break out the slinky until the morning of departure for stays less than a few days.

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grey tank, tank

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