How Much Water Capacity Do You Need?

What water capacities does DETRAILERS normally build?

DETRAILERS' normal total onboard water capacities are 60, 100, 200, 400, 550, and 1,100 gallons. These are the capacities most customers actually end up with — not a universal sizing chart, but a real picture of the range DETRAILERS builds day to day. 60 gallons is currently the smallest normal capacity, and 1,100 gallons is the largest — but 1,100 gallons isn't an absolute maximum. DETRAILERS can build systems with greater water capacity when the application requires it.

DETRAILERS can also build a 300-gallon system, but it's an uncommon request — most customers land on one of the normal capacities above rather than 300 gallons specifically. It comes up later in this guide as an example of DETRAILERS' multiple-tank design practice, not as part of the typical lineup.

What actually determines the right tank size?

The correct capacity depends on several things together:

• The cleaning application itself
• Equipment GPM — the rate of water consumption
• Expected water consumption for the work
• Availability of water at the jobsite
• Required self-contained operating time
• Trailer or vehicle carrying capacity
• Weight distribution
• Overall system configuration

That's why this guide doesn't hand you a formula — determining the right capacity takes a real conversation about what you're actually going to do with the system.

Water availability at the jobsite matters more than people expect. Residential pressure washing and soft washing jobs typically have water available at the property, though that's not a guarantee on every job. Other applications are different by nature — washing oil pumping rigs, for example, can mean working nowhere near a usable water source, which makes onboard, self-contained water capacity much more important. Equipment GPM factors in too: higher water consumption draws down your onboard supply faster, regardless of how many people are operating the system. Running a second operator doesn't automatically mean you need twice the water capacity — the real driver is how much water the equipment actually consumes and how long you need to run before refilling.

Why systems over 200 gallons use multiple tanks

DETRAILERS' normal 60-, 100-, and 200-gallon configurations are single-tank systems. Anything over 200 gallons uses multiple tanks rather than one large tank. Splitting larger capacities among multiple tanks helps DETRAILERS manage weight distribution and creates a natural baffling effect by dividing the water volume, instead of allowing the entire volume to move as one large mass.

A 300-gallon system can be built as two 150-gallon tanks, but 300 gallons is an uncommon total capacity request and is not part of the normal lineup above.

Why the weight of the water matters

Selecting water capacity isn't simply about carrying enough water to perform the work. The trailer, truck or skid installation also has to be designed around the loaded weight of the system. DETRAILERS considers factors including trailer GVWR/load capacity, axle capacity, tire capacity, frame/skid construction, weight distribution, tongue weight where applicable, and pickup payload capacity for truck-bed/skid systems. This applies to both trailer-mounted systems and pickup-bed/skid-mounted systems — a system physically fitting in a pickup bed doesn't establish that the truck has sufficient payload capacity to safely carry it once loaded.

Water itself is heavy: a U.S. gallon of water weighs approximately 8.34 pounds. At that rate, 200 gallons of water weighs approximately 1,668 lb, 550 gallons weighs approximately 4,587 lb, and 1,100 gallons weighs approximately 9,174 lb. Those figures are the water alone — they don't include the weight of the tanks, pressure washer(s), burner, fuel, hose reels, hoses, plumbing, batteries/electrical equipment, frame/skid, trailer, or other equipment. These numbers aren't a substitute for a real weight assessment: actual GVWR, axle and tire ratings, payload, tongue weight, and the complete loaded configuration all have to be considered for a specific build.

Using multiple tanks on systems over 200 gallons gives DETRAILERS more ability to manage where that water weight is carried and how it's distributed throughout the system, in addition to the baffling effect described above. It doesn't change the underlying carrying limits of the trailer, axles, tires or vehicle — multiple tanks help distribute the weight that's there, not increase how much weight the system is rated to carry.

One issue that can be overlooked in a home-built wash system is the weight of the water itself. DETRAILERS designs the trailer or skid around the loaded system — not simply around whether the equipment physically fits.

Matching capacity to your application

Auto detailing and mobile car washing commonly fall toward the lower end of DETRAILERS' range, including 60- and 100-gallon systems. That's a common pattern, not a universal recommendation — the correct capacity still depends on the application, water availability, equipment consumption, and overall system configuration, the same way it does for every application in this guide.

Higher-water-demand applications, longer self-contained operating requirements, larger surfaces, and high-volume or big-rig work can push a system toward greater onboard water capacity. For how application type drives other equipment decisions, see our hot water vs. cold water guide and fleet washing vs. truck washing guide.

Does a bigger tank mean a better system?

Not automatically. Additional capacity adds substantial water weight and can add cost and complexity without providing any benefit if your actual application doesn't require it. The goal isn't to sell the biggest possible system — it's to understand your intended work, needs, and budget so the system is neither unnecessarily oversized nor undersized for what you actually plan to do. This is the same philosophy covered in our guide to starting a pressure washing business.

How capacity fits into the rest of your system

Tank size is one part of the overall system design, alongside hot vs. cold water, trailer vs. truck mounting, equipment flow, single- vs. multi-line configuration, your application, water availability, and carrying capacity. These decisions are related and shouldn't be made in isolation. Our guide to starting a pressure washing business covers the rest of that picture.