Install and plumb your discharge/dump valves out the Drivers side of your trailer.  This is for campsite sewer hook-ups, and proper traffic flow at public dump stations.

Securing your waste water tanks is of uttermost importance.  If you are using tanks of any size, you need heavy duty support.  If you think you can stretch 3 or 4 rows of plumber strapping across two sections of trailer framing and call that good… ready for a real stinky situation.

Plumber strapping, that 3/4 inch wide stuff with perforated holes down its length, might be great for strapping up pipes that have little to no weight.  I have seen this used to hold up 15 to 30 gallon tanks by some that haven’t thought this through.  I just hope I am not following them down the road some day.  I personally wouldn’t even hang pipes with that stuff under a trailer.

Often the Cargo Trailer Conversion ends up having two waste holding tanks.  Both in an average size of 25 gallons each.

Lets do the weight math on a full 25 gallon tank.  @7.5 lbs per gallon.  That equates to 7.5X25 or roughly 187lbs.   The force of that weight is compounded with any type of up and down movement such as a loose tank, or bumps in the road.

If you think plumbers strapping is going to hold that kind of weight [oh sure maybe it will for awhile], you best carry your elbow length rubber gloves and lots of clean up gear.  A full tank bouncing around, held in place with inadequate hangers is going to eventually end up on the road and tear off a whole lot of stuff in the process.

Even if you say you have no intentions of traveling with anything in your tanks, that probably will not be the case at times.   Situations always come up.  Boondocking is an example.  Or a campground Dump Station is closed or non existent.  I have even camped in cold weather and ended up with a blockage and couldn’t dump until I was at warmer temps, at a lower elevation.

The point being, your tanks need hung on some type of substantial hanging system.  Over kill is better than a cheap half fast job.  You need to secure your tanks in such a way, there is no up and down play or movement.   Then the tank needs secured to prevent front and back movement, and side to side movement.  Otherwise kiss any joints goodbye somewhere along the way.

Think along the lines of heavy threaded rods, angle iron, or heavy duty electrical strut.  Through the frame or welded, verses anything that clamps on.

Failing to secure the tanks from all directions of movement may result in the tank ending up on the road, or at a minimum, cracking the tank itself, a drain pipe, or a vent pipe.

Many methods can be used.  One method is to create a hanger system that uses the existing trailer frame.   Hanging bolts, and using angle iron as cross supports.  Then blocking the 4 sides by whatever means you can to prevent any movement in the 4 side directions.

Not seen in this photo is a square 2×4 frame that is up against the bottom of the sub-floor.  It was made and attached before the tanks was draw up and into it.   This tank is supported and movement prevented top to bottom, and any side movement in any direction.

Double nuts and use nylon inserted locking nuts.  Make it fail safe.