Dear Dave,
I know weight capacities have been addressed, but one question that I have never seen answered in my 36 years of RVing is this: Is the liquid in holding tanks counted against the GVWR when parked? It would when traveling, for sure. But when stationary on jacks or blocks, I’m not sure it needs to be. Thanks. —Dave, 2000 Southwind 34N
Dear Dave,
Great question, as most articles and blogs talk about GVWR while driving and don’t address what happens sitting at the campground. Yes, liquid in the holding tanks must be included in the total weight of the rig. For years, the consensus has been you can put any weight in you want once you get to the campground, and for the most part, that is true. However, there are some precautions you need to consider.
How GVWR is classified and what it means
Gross Vehicle Weight Rating (GVWR) is classified as the maximum weight a unit can weigh with all liquids and cargo. In a motorized vehicle, it also includes passengers, as they will be in the unit while driving. With a trailer, the passenger “should” be in the tow vehicle and that weight is calculated in the tow vehicle weight ratings. For the most part, the GVWR and any additional weight in the holding tanks pertain to driving down the road and the weight that will affect the tires, axles, drive train, and braking capacity.
According to the RV Safety & Education Foundation (RVSEF) and most chassis manufacturers, it is a good practice to actually deduct 10% off maximum GVWR, as you do not want to be fully loaded in extreme conditions such as hills, hot days, and other weather conditions.
Typically, once you get to the campground there is not much more weight you can put into the camper other than fresh water and some people. I recommend weighing the rig at a CAT Scale once you get all the food, blankets, grills, and accessories packed for the trip so you know what the rig will weigh going down the road. If you have a motorized vehicle, either have the people in the rig or ask for “accurate” weights to calculate that as well.
How much does liquid weigh?
According to the data obtained from RVSEF, liquids have the following weights:
- Fresh water – 8.3 lbs. per gallon
- Liquid propane (LP) – 4.2 lbs. per gallon
- Gasoline – 6.0 lbs. per gallon
- Diesel fuel – 6.6 lbs. per gallon
So a 100-gallon water tank can add 830 lbs. to the overall weight. Then you have to factor in the black and gray water tanks, if you fill them up. I would estimate the gray water tank, which is shower and sink wastewater, would be about the same as the fresh water. However, the black water tank might be more. If anyone out there wants to research this and do the math, go ahead… I’m not going there!
Typically, you would not have a full fresh water tank and full black and gray unless you filled the fresh water tank either before leaving or at the campground, and then hooked up to city water and used that to fill the other tanks. If you have a trailer or 5th wheel, you will then need to factor in the weight of the people that will be inside.
Jacks, stabilizers and weight
A unit that is sitting at a campsite with jacks that level and stabilize the unit would not be affected by any additional weight. However, you also indicated blocks, which also makes me want to address trailers that only have cheap stabilizers or use wood or plastic blocks to level.
Since you have a 2000 Southwind, your jacks are most likely the Power Gear hydraulic jacks that can handle weight and wind resistance. However, most travel trailers have cheap scissor jacks that are not intended to handle any weight, just stabilize, and they don’t do a good job at that. Plus, if those jacks are not supporting the frame, additional weight will be going on the tires. If you are at maximum weight before adding the liquid, that puts stress on the tires and axles.
Roger Marble, our tire expert, had a great article addressing this recently stating that covering tires for UV protection and other stress issues doesn’t happen immediately, but will affect the longevity down the road. Same thing with bearings and axles that can get bent due to weight. And if you are simply using blocks under the wheels to level the rig, that added weight can impact the longevity of those components.
Bottom line: If you are confident the jacks are supporting the critical components, the additional weight should not be a factor. However, make sure you don’t pack up and take that weight with you when you leave the campground!
You might also enjoy this
Why your RV’s GVWR is different than its GAWR
Read more from Dave here.
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The proposal, that the weight of the black, gray and fresh water tanks should not matter if in a stationary position, seems logical. But those tanks, when full, will be the heaviest objects in the RV and the stress on their securing straps will be great. Given the industry’s “just enough is good enough” mindset, I’m left with a less than warm and fuzzy feeling about the durability of those straps over time.
When I go to the CAT scales I weigh the Airstream trailer and my TV while connected to each other. My GVWR is 7600 and the scales say my trailer axles are holding 6800#. Sounds good to go! Let’s roll! But doesn’t the trailer actual weight include the tongue weight (about 900# more), which would put the trailer actual weight above the GVWR? In addition, the trailer actual weight at the camp ground would again include the additional load on the front jack which is probably close to my known tongue weight of 900#. And then add the people (family of 4 about 500#) and my 36 gallons of fresh water (288#). That’s now 8488#, well above GVWR. So does the max weight allowed on the vehicle include the tongue weight or does it not. I’m suspecting it does not since my trailer dry weight (empty) as it comes is 6306# and tongue weight is listed as 850#. So putting nothing else but me and my wife (300#) and 36 gallons of water we would be at 7744#, again exceeding my GVWR.
Tongue weight is considered cargo weight for your tow vehicle.
Thank you! Or cargo for my jack when at the campsite I presume. Good to know we are within limits after all. Thanks for the article!
Remember that if you aren’t at a full hookup site, you will be pulling the trailer with full grey and black tanks to the dumping station – possibly over the roughest roads of the trip.