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Old 02-12-2014, 03:15 PM   #1
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Question One waste tank vs black & grey

Been researching B class RV's. The deal killer for our camping style is the small, typically 10 gallon black tank. The typical grey tank runs in the 25 gallon range.
I wonder why there cannot be a single waste water tank of say 35 gallons in this case. For our use, 35 gallons combined would be just fine.
I realize that sometimes one tank is placed on each side of the rear axle because of the floorplan.
For discussion purposes, lets assume the floorplan does not demand this tank separation.
Is there a reason I'm missing why one waste tank would not work?

The same question could apply to all RV's but it's especially relevant with very small ones.


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Old 02-12-2014, 03:24 PM   #2
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ed, iu have a friend with a 40' motorhome that has done just that. He reports no negative issues. You could install a small water pump to move gray water to the black tank.

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Old 02-12-2014, 03:33 PM   #3
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Back in the 70's one tank was common - the GMC also had a drain valve you could crack open from the inside while traveling down the road to slowly empty the tank while driving along. Motorcycles beware!
Now that GMC was a futuristic motorhome (455 olds engine, chain driven FWD xmission, very low to the ground floor), air bag suspension.
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Old 02-12-2014, 09:21 PM   #4
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One thing that might not be too pleasant with a single tank is that you won't have any relatively clean gray water to flush the hose.
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Old 02-16-2014, 07:16 AM   #5
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Well two reasons:

First having your gray sources connected to a black tank gives more pathways for stinky gases to enter the inside of the coach. Also, if it over-fills, you've got poo coming up your sink and shower drains. Yuk!

Secondly, 10 gallons is quite a bit of black water. You should be able to go at least a week between dumpings. If you get in a situation where your gray tank is full, in some places you can just dump it out on the ground (it's just soapy water after all). Some will be agast at such an idea, but you'll find threads on here discussing it. If you had a combined tank, that possibility would be out of the question.

I'd be more concerned about the size of the fresh water tank. You are most likely to run that dry before full tanks are really an issue.
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Old 03-09-2014, 12:05 PM   #6
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I would love to have a larger grey tank than the black. Ours is the same size--not smart imho. We NEVER have filled the black tank before the grey, and we wash our dishes in a dish pan and dump the water in the toilet to save space in the grey tank--and in all our previous mohos. I have seen specs on some smaller rigs that actually have a larger black tank than the grey---where do these "design engineers" come up with this stuff!

If you always visit RV parks, vs State Parks or boondocking a combined tank would be fine--but if you visit the others, as wincrasher mentioned--often times you can dump you grey water on the ground in an emergency--but with a combined tank you could not. In fact we stayed at an RV park in central PA once that the owner told us to just dump our grey water on the ground!

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