Guide · computed from 1,628 verified floorplans
Travel Trailer Tank Sizes: Fresh, Grey and Black Water by Length
Published fresh, grey and black tank capacities, grouped by trailer length, and what the water in them weighs against your cargo capacity.
Short answer. The median travel trailer here carries a 45-gallon fresh tank (n=1,219), a 40-gallon grey tank (n=1,211) and a 35-gallon black tank (n=1,145). Fifth wheels run larger: medians 75, 87 and 50 gallons (n=403, 402, 386). A full fresh tank of the median travel-trailer size weighs about 374 lb, and that weight counts against the trailer’s cargo capacity.
Why tank size is a towing number
Federal rules require an RV trailer’s load label to carry the statement “CAUTION: A full load of water equals XXX kg or XXX lbs of cargo @ 1 kg/L (8.3 lb/gal)” (49 CFR 571.110 S9.3.8), and they say: “If the vehicle is a recreation vehicle trailer and is equipped with an on-board potable water supply, the weight of such on-board water must be treated as cargo.”
So every gallon in the fresh tank comes out of the cargo capacity printed on that label, and it adds to the loaded weight your vehicle tows. The “Full fresh tank” column below multiplies each band’s median fresh tank by 8.3 lb per gallon, the label’s own conversion.
Travel trailer tank sizes by length
| Length | Floorplans | Fresh, gal | Grey, gal | Black, gal | Full fresh tank, lb |
|---|---|---|---|---|---|
| 12 to under 16 ft | 8 | 27.5 (18–31; n=8) | 24.5 (6–34; n=8) | 12 (12–34; n=3) | 228 |
| 16 to under 20 ft | 48 | 34 (16–55; n=47) | 30 (19–45; n=45) | 30 (15–42; n=45) | 282 |
| 20 to under 24 ft | 224 | 31 (20–90; n=223) | 30 (19.9–96; n=223) | 30 (17–45; n=208) | 257 |
| 24 to under 28 ft | 195 | 52 (12–96; n=194) | 39 (12–82; n=193) | 32 (4–57; n=176) | 432 |
| 28 to under 32 ft | 282 | 52 (37–106; n=280) | 44.5 (30–98; n=276) | 37 (28–68; n=260) | 432 |
| 32 to under 36 ft | 218 | 52 (38–110; n=218) | 60 (28–117; n=216) | 38 (28–90; n=207) | 432 |
| 36 to under 40 ft | 171 | 52 (38–102; n=170) | 70 (30–131; n=171) | 38 (28–100; n=167) | 432 |
| 40 to under 44 ft | 64 | 43 (38–86; n=64) | 70 (32.5–131; n=64) | 40 (30–106; n=64) | 357 |
| 44 to under 48 ft | 13 | 40 (40–55; n=13) | 80 (40–132; n=13) | 70 (40–88; n=13) | 332 |
Median, then the range and the number of floorplans that publish each tank, n. “Floorplans” counts every travel trailer in the band; a maker that publishes no figure for a tank is left out of that tank’s median. 1 published fresh-tank figure is flagged as physically implausible and left out (conflicts).
Fifth wheel tank sizes by length
| Length | Floorplans | Fresh, gal | Grey, gal | Black, gal | Full fresh tank, lb |
|---|---|---|---|---|---|
| 28 to under 32 ft | 36 | 54 (48–102; n=36) | 78 (30–120; n=36) | 39 (30–45; n=32) | 448 |
| 32 to under 36 ft | 71 | 64 (48–150; n=71) | 82 (38–106; n=71) | 44 (30–53; n=64) | 531 |
| 36 to under 40 ft | 80 | 75 (49–160; n=80) | 87 (38–156; n=80) | 50 (30–104; n=76) | 622 |
| 40 to under 44 ft | 156 | 75 (49–150; n=156) | 88 (50–159; n=155) | 71 (30–106; n=155) | 622 |
| 44 to under 48 ft | 45 | 106 (49–160; n=45) | 97 (38–156; n=45) | 80 (32–104; n=45) | 880 |
The largest fresh tanks among travel trailers here
| Floorplan | Brand | Fresh, gal | Grey, gal | Black, gal | Length |
|---|---|---|---|---|---|
| Alta 2870KTH | East to West | 110 | 60 | 30 | 33' 1" |
| Alta 2400KTH | East to West | 106 | 60 | 30 | 28' 1" |
| Cyclone 2214 | Heartland | 106 | 74 | 37 | 28' 1" |
| Cyclone 2615 | Heartland | 106 | 74 | 37 | 34' 8" |
| Seismic 214 | Jayco | 106 | 74 | 37 | Not published |
| Seismic 265 | Jayco | 106 | 67 | 40 | Not published |
| Nightfall 22N | Forest River | 102 | 80 | 40 | 28' 6" |
| Nightfall 24N | Forest River | 102 | 80 | 40 | 30' 0" |
Weights by length are on the weight chart.
Common questions
How big is a travel trailer fresh water tank?
The median published fresh-water tank among the 1,219 travel trailers in this catalogue that publish one is 45 gallons (smallest 12, largest 110). For fifth wheels the median is 75 gallons (n=403).
How much does a full fresh water tank weigh?
Federal labelling rules convert water at 8.3 lb per gallon (49 CFR 571.110 S9.3.8). At that rate the median travel-trailer fresh tank here, 45 gallons, holds about 374 lb of water, and the rule counts that water as cargo.
What size are grey and black tanks on a travel trailer?
Medians across the travel trailers here that publish them: grey 40 gallons (n=1,211) and black 35 gallons (n=1,145). Some makers publish one combined waste tank; each floorplan page shows its tanks exactly as published.
Browse
- Travel trailers
- Fifth wheels
- Travel trailers under 3,500 lb
- Travel trailers under 5,000 lb
- Travel trailers 5,000–7,000 lb
- Travel trailers over 7,000 lb
- Fifth wheels under 10,000 lb
- Travel trailers under 22 ft
- Travel trailers that sleep 8+
- Toy haulers
- Destination trailers
Figures on this page are computed from the site’s own verified-specs dataset (1,628 floorplans; generated 2026-10-21), which is read from the floorplan pages and their named manufacturer and dealer-network sources. Dry, hitch and pin weights are as published, before options, water and cargo. Two published hitch figures that are physically implausible are printed on their pages with a flag and left out of every statistic here (conflicts). How the data is verified. Built 19 Oct 2026.