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Old 10-18-2017, 11:18 PM   #1
1 Rivet Member
1978 31' Sovereign
Portland , Oregon
Join Date: Jul 2017
Posts: 16
Center bath Sovereign - converting black tank to grey tank

Hey there. Newbie here, this is my first post to Airforums. My wife and I bought a 1978 Airstream Sovereign (Center bath) over the summer and are planning on hitting the road with our 2 young boys and traveling full time while my wife takes the occasional travel nursing assignment once I complete a total renovation. I have been lurking on this site for months and the information I have found here has been invaluable.

So far I have the trailer completely gutted and am preparing to remove the shell using gantry's hopefully this weekend to get to work on repairing frame rot and installing new sub floor.

My first question on this forum has to do with the holding tanks. I have not been able to locate the info I'm looking for on these forums. We will be installing a composting toilet (either Airhead or nature's head) so I will need to convert the black tank to a grey tank (at least I think so). I'm assuming I will need to ditch the black tank and purchase a new tank but I'm not sure.

Lot's of questions here:

-Will we need two grey tanks or should I be adding more fresh water storage?
-If I need two grey tanks, how do I go about converting black tank to grey tank?

Hopefully this question is not too generic.

I would add photos but apparently it's not as easy as it sounds. I will have to research that next.

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Old 10-22-2017, 06:30 AM   #2
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1954 25' Cruiser
Bern - Thun , Berner Oberland
Join Date: Aug 2014
Posts: 87
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Blog Entries: 1

I don't understand the problem. You install a new toilet that doesn't need a tank any more, so it doesn't need a black water tank. Why do you have to have two greywater tanks? Are the existing containers too small? In principle, you lock the black water tank and the rest works as before?!?
Greetings from Switzerland - Werner
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Old 11-01-2017, 11:46 PM   #3
1 Rivet Member
1978 31' Sovereign
Portland , Oregon
Join Date: Jul 2017
Posts: 16
Further Clarification

Please allow me to further clarify. I finally got the sub floor removed today and can clearly see what tanks I have and where they are located.

I have 1 ea. black (behind rear axle), grey (at rear axle) and fresh water storage (at front axle). Since I won't have a toilet I no longer need a black tank. We plan on doing a lot of boondocking so I would like to maximize both my fresh water and grey water capacity. My shell is currently off so I have full access to make necessary modifications.

1. based on everyone's experience is there a good rule of thumb ratio for fresh water to grey storage? I have never RV'd before but a 1:1 ratio seems logical to me.
2. Can I remove the black tank and install a grey tank in it's place? What's the best way to plumb 2 tanks together?
3. Can I add another fresh water tank or swap out the current one for a larger one for more capacity?
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