Thread Tools Search this Thread Display Modes
Old 09-10-2011, 09:38 AM   #1
1 Rivet Member
Toronto , Ontario
Join Date: Aug 2011
Posts: 6
Convert black tank to grey?


I have a 73 Overlander with a rear bath that I am gutting and modernizing. I would like to add a grey water system, and had a bit of an idea this morning.

Since we will be re-configuring the entire trailer, would this scenario be possible:

Leave the existing black water tank in place on the rear street side of the trailer. Make the black tank my new grey tank, and move the shower to the street side.

Add a new above-floor black tank on the curb side and a new low-height toilet to dump directly into the new tank.

This would eliminate dropping the belly, ripping up the subfloor (which is in excellent condition), etc.

Would the capacity of the old black tank be adequate for use as a grey water system? I could run my new drain entrance plumbing under the new shower base. I just can't find the black tank capacity information anywhere.

Ideas, ideas...

thanks -Jamie

Jamiep is offline   Reply With Quote
Old 09-10-2011, 10:06 AM   #2
Rivet Master
Minno's Avatar

1972 31' Sovereign
Lexington , Minnesota
Join Date: Feb 2009
Posts: 3,371
Do you know the dimensions of the tank?

If you do, then take the total cubic inches and divide by 231 for gallons. That will give you an approximate answer since most tank dimensions are for the outside of the tank, and wall thickness take some of that away. Plus, you have the drain pipe from the tank to the dump valve, which adds capacity.

If you don't know the dimensions, one way to figure it out would be to start dumping gallons of water into the tank, one gallon at a time, until it's full. Plastic 1 gal milk jugs would work. Might take a bit of time, but you'll have an accurate answer.


Minno is offline   Reply With Quote
Old 09-10-2011, 10:50 AM   #3
Rivet Master
Melody Ranch's Avatar
1956 22' Flying Cloud
1953 32' Liner
1955 22' Safari
Valley View , Texas
Join Date: Jan 2006
Posts: 3,971
Images: 78
Send a message via Skype™ to Melody Ranch
How are you planning the dump system for the new black tank?
"If it can't be reduced, reused, repaired, rebuilt, refurbished, refinished, resold, recycled or composted
then it should be restricted, redesigned or removed from production."
Melody Ranch is offline   Reply With Quote
Old 09-10-2011, 01:05 PM   #4
1 Rivet Member
Toronto , Ontario
Join Date: Aug 2011
Posts: 6
I was thinking of connecting to the main sewer connection through some of the existing holes in the floor from the old shower, etc.

I don't have access to see the size of the tank. I bought the trailer, which hasn't been used in 15 years and have it parked in a utility yard right now, and in the process of tearing it apart realized that the previous owner has left me a 15 year old full tank of presents...

so now I have to find somewhere in downtown toronto to dump a trailer tank...a heavy task (pun intended...)
Jamiep is offline   Reply With Quote
Old 09-10-2011, 01:58 PM   #5
Rivet Master
HowieE's Avatar
1991 34' Excella
Princeton , New Jersey
Join Date: Aug 2003
Posts: 6,895
Images: 12
There are no mechanical reasons why you can't change the use of the black water tank.

You want to consider that your new tank has a 3 in. drain line and not rely on the old 1 1/2 in. shower drain.

Most homes have a sewer clean out at the curb.That is what I use to dump many times when there is a line in the camp ground.

In all likely hood the floor will have to come up or the pan down to run the larger sewer line so plan with that in mind and you may not have to use a special toilet.

Another trick I have used is to connect the tanks with a small pipe from the bottom of the gray tank to the top of the black tank. Excess gray water just flows over to the black tank and extends things on a long weekend. Starting with a small tank on the gray side makes this a useful consideration.
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles

HowieE is offline   Reply With Quote
Old 09-10-2011, 02:18 PM   #6
Join Date: Jun 2010
Posts: 2,601
Hi Jamie welcome to the forums from a fellow Ontarian. I'm a couple of hours north west of the big smoke.
The first problem I can see is capacity. The black tank in your trailer is probably 12 gals. That would be way too small for a grey tank. One shower and the tank will be full. Even as a black tank it is too small to be of any practical use. Airstream never published tank capacities from back in the 70's. They simply state the tank size as "about one weeks" capacity. Boy were they wrong on that estimate.
I think as long as your getting in to it the best way would be to drop the belly and replace the black tank with a larger one and add a grey tank or two which will give you adequete storage capacity for normal use. You can then easily replumb the imput to the tanks and the outlet drain system.
wasagachris is offline   Reply With Quote
Old 09-10-2011, 03:07 PM   #7
Rivet Master
DaveFL's Avatar
2000 31' Land Yacht
Central , Florida
Join Date: Aug 2007
Posts: 1,483
Images: 15
Black tanks are without an elbow, toilet dumps straight in using the valve to seal off gases, grey tanks use water sealing elbow. My grey tank is twice the size of the black and it is the limiting factor for length of time before dumping. Make sure you consider where the vent stack will go from a new black tank.
DaveFL is offline   Reply With Quote
Old 09-10-2011, 09:03 PM   #8
Rivet Master
Minno's Avatar

1972 31' Sovereign
Lexington , Minnesota
Join Date: Feb 2009
Posts: 3,371
Our black tank in a '72 Sovereign is an 18 gal. You might get lucky with the undumped black tank as we were - it was all composted black liquid without any odor when we discovered it and dumped. If the liquid evaporated or leaked, you'll have cement. Might take awhile to soften up to dump. Grey tanks usually are at least twice the capacity of the black tank. We never have to dump because the black tank is full, it's always the grey that fills up first.

Minno is offline   Reply With Quote
Old 09-10-2011, 09:17 PM   #9
Rivet Master
Minno's Avatar

1972 31' Sovereign
Lexington , Minnesota
Join Date: Feb 2009
Posts: 3,371
Hey,we just remembered that we have our old black water tank. Its still watertight and in good shape. 18 gal with a rear outlet. Free to a good home - you pay shipping...
oops- posted in wrong thread. Not sure how to delete.

Minno is offline   Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Grey tank inlet help? brattwurzt Waste Systems, Tanks & Totes 1 08-21-2011 07:54 PM
How much black / grey is enough? Darkspeed Waste Systems, Tanks & Totes 5 05-26-2011 07:39 AM
No black tank in 62 Tradewind tlsmit1 Waste Systems, Tanks & Totes 1 05-15-2011 04:53 PM
Adding a larger grey tank to a 78 Tradewind johnhh Waste Systems, Tanks & Totes 3 04-04-2011 12:43 PM

Featured Campgrounds

Reviews provided by

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 03:11 PM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.