New black and grey tanks... how do you size them

[Debnw]

We are progressing on the restoration of our 72 Safari. frame repairesd and ready to put in new tanks...So my quesion is.
1) I can replace the original pie shaped black tank (see pic) that sits on the floor uoder the toilet (16 or 17 gallons). and also found 16 gallon tanks for the grey water from Vintagetrailer. These tanks are small enough that they will stay within the frame of trailer.
The only concern is the size of black tank and the flatness of the tank. All new tanks are tapered and slope to the drain. This one doesn't. Does the bottom drain REALLY empty the tank completely????

2) I can replace with aftermarket tanks (Black-25gal/Grey-32gal) that will be mounted under the floor and hang approx 3 inches below the frame (like the newer AS do). The sides of the tanks will be protected by the reinforcement plates for the axle and tail of trailer frame. My concern is that things thrown up from the road will puncture the tanks.

Thoughts

Bruce

The black would be at the back in the last gap. The grey would be placed in the gap just past the second axle....

[M2HB]

As far as capacity goes, it really depends on what you are going to use it for. In my opinion, it pays to get as much capacity as you can while you are doing it. Remember, each gallon weighs 8.33 pounds, and that adds up fast. You need to have a mounting system that is strong enough to hold the weight, and you have to deal with the light AS frame.

[purman]

Mine hang down 5" in between the axles and behind them. They are 30 and 35 gallon tanks.
Look here for tanks and other online sites.

RV Holding Tanks - Water & Waste

and you can see what I did here.
http://www.airforums.com/forums/f174...8-a-90934.html

[Debnw]

Guys, Thanks! to keep the grey tanks lite and better distributed I was looking at puchasing two 16 gallon tanks (32 total)and tie them together at their discharge. YEs I think I could use one larger tank....just dont like the large drop below the frame. Any issues you can think of....other than how to get the level sensors to read accurately....
Using the two tanks will allow min drop below the frame (2 inches worse case) like the water tank currently does. With the split I can place one before an one after the second axle. Then the only added weight at the back of the trailer, would be the larger black tank.

Yea... O know...PICS....soon as I get the tanks in, I post some pics of the tanks and freshly painted frame.

[purman]

I tied my two 30+ gal tanks together before the dump valve. The forward one has the kitchen sink dump into I and the rear one has the bathroom sink and shower dump into it. Because of this they self equalize. You only need a sensor on one of the tanks to get an accurate reading. I found a 26 gallon tank that fit in my frame and only hung down 2". This is my extra fresh water tank. That's right I have 3 tanks under the trailer and one under the front bed. I can put 65 gallons of water, and grey storage, in at a camp site with no water hook ups. Saves me trips to the dump station to dump and full up all the time. 4 girls , they like their water

[Silverflames]

On my 1969 Ambassador the back 3 feet of the frame was extend down by about 3" to accommodate a larger black holding tank. I believe that was an original design, but don't quote me on that. While doing the frame repairs, I extended the frame down three inches form the back of the trailer all the way to axle mounting plate. This allowed me to install 7" and 8" tall tanks. My grey and back tank are 8" (27 gal) at the tallest point and my fresh water is 7" (30 Gal) but with the plywood base and insulation it is almost 8".

http://www.airforums.com/forums/f36/rear-end-separation-short-term-fix-90941-3.html