How do I find out how large the holding tanks are on my RV?

The quick answer is to consult the specifications section of the brochure for your make and model of RV. You might also check the manufacturer’s website to see if you can download a PDF document of the brochure or other technical documents.

Tank sizes don’t vary too much from year to year in most brands and models of RV’s so if you can’t find the exact year of your model, a year before or after is very likely to have the same size tanks.

A good rule of thumb in figuring tank capacity is that your main black and gray tank, when combined together in gallons of capacity, will just about equal the capacity of your freshwater tank. Of course, for RV’s with more than just one gray or black tank, this general and very approximate rule won’t apply.

RV’s also tend to have larger gray water tanks than black water tanks and as a general rule, tank capacity for different types of RVs is as follows:

Travel trailers: 30-50 gallons freshwater, 25-40 gallons black, 30-50 gallons gray

5th wheels: 80-100 gallons freshwater, 40-60 gallons black, 40-75 gallons gray

Motorcoaches: 80-150 gallons freshwater, 40-75 gallons black, 40-100 gallons gray

Again, these are approximations and your manufacturer’s documentation should be referenced first.