by Grummy » Thu Sep 12, 2019 2:01 pm
My trailer is also low and prefer that for my needs. I too pondered over just how and where to fit the tank situation. I also considered your proposal, but in my case, I had no good place to put the tank(s) when en-route. Any space I have on the trailer itself, like behind the axles or tongue need other things located there, and I pull with a VAN and certainly did not want to store those inside even if they do seal well.
Then considering that I might be camped where I can not empty them right away, I'd have to load or store them half full or more. That just seemed like a royal pain and I never gave it another thought.
I see many people work hard to keep their tanks inside if they are going to traverse colder climates, so that too has to be considered. If your too low to get the full capacity you hope to have, nothing stops us from locating a tank that is partway inside and only the amount sticking below the frame that still allows the clearance you need. Just have to pick a tank that fits between the rails and build the proper hanger system.
In my case, I am pretty "Small" with only a 6x12. I opted for a self contained 5 gallon porta-potti for the heavy stuff. I can opt to dump early (light) or full when necessary depending on environment, and ALWAYS look for my use options before filling it.
I located a shallow 15 gallon GREY tank fully under and between the frame cross members, right behind the axle for sink drainage, while a 10-12 gallon fresh tank still needs to be installed just ahead of the axle. This leaves room for 3+ gallons of incidentals poured in the sink (leftover soda, coffee, etc.).
That 10-12 gallon will be used primarily for washing things as I find it really simple and safe to just buy the 4 or 5 gallon fresh water exchange tanks rather than bother to keep the fresh tank 100% drinking safe constantly.
Personally, I think money is best spent on mounted tanks up front. FInd a way to fit them, find a way to figure out what you really need for capacities. Driving around with a thousand pounds of liquid unnecessarily doesn't make sense either. It hurts once, but then you do not always have that additional set of full tanks to hassle with by hand.