A water tank trailer is the most practical way to move large volumes of water across a property or job site — no plumbing required, no permanent installation, no waiting for a city hookup. Whether you're a pressure washing contractor needing an independent water source, a rancher topping off stock tanks across a spread, or a construction crew managing dust suppression, a tank trailer is the right tool.
This guide covers the two most common sizes — 500 and 1,000 gallons — along with how to build your own setup, what pump to pair with your tank, and how to evaluate used trailers.
Choosing Your Tank Size
The right trailer size comes down to what you're doing and how far you're going between refills.
| Use Case | Recommended Size | Why |
|---|---|---|
| Pressure washing (solo, half-day jobs) | 100–200 gal | Fits on a small utility trailer; easy to haul with a half-ton truck |
| Pressure washing (full-day, commercial) | 500 gal | Full day of washing without refilling; buffer for low-flow hose bibs |
| Mobile auto detailing | 100–200 gal | Enough for 10–20 full detail washes per fill |
| Livestock water delivery | 500–1,000 gal | Fills stock tanks in one trip across a property |
| Construction site supply | 1,000 gal | Concrete mixing, dust suppression, crew supply for a full work day |
| Emergency/wildfire water transport | 1,000 gal | Enough volume to matter; critical for rural fire suppression assist |
Size Guides
The Right Tank for a Trailer
Not every water tank is designed for transport. Vertical storage tanks are not trailer-appropriate — they have a high center of gravity and no provisions for tie-down. You need a horizontal transport tank (also called a leg tank or cradle tank).
Norwesco Horizontal Transport Tanks
Norwesco produces the industry-standard horizontal transport tanks in black UV-stabilized polyethylene. The key feature is a flat bottom section and molded-in cradle ribs that allow secure mounting with standard tank straps. Available in 165, 225, 305, 500, and 1,025 gallon sizes. All are rated for potable water. Available at Tractor Supply, Tank Depot, and Farm & Fleet stores.
Snyder Industries Horizontal Tanks
Snyder's horizontal transport tanks are the other major name in this category. Build quality is comparable to Norwesco — both use virgin FDA-grade HDPE resin. Snyder's tanks are occasionally slightly cheaper depending on retailer and region. Tank Depot carries both brands and can help you compare current pricing.
Pumps: What to Run on a Water Trailer
12V Electric Transfer Pumps — Easiest Setup
A 12V electric transfer pump wired to your truck battery (or a separate battery box on the trailer) is the simplest and most common setup for livestock watering and agricultural water delivery. Look for pumps rated 5–15 GPM at low pressure — enough to fill a stock tank or water trough quickly. Flojet and SHURflo make reliable options in the $80–$200 range.
Gas-Powered Trash Pumps — High Volume
For construction site water supply or filling large stock tanks fast, a gas-powered trash pump (Honda GX160 or similar) rated 100–160 GPM is the tool. These run off a separate engine mounted to the trailer frame and can empty a 500-gallon tank in under 5 minutes. Expect to pay $300–$600 for a quality unit from Northern Tool or Tractor Supply.
Pressure Washer Buffer Setup
If you're pairing the trailer with a pressure washer, you're not running a transfer pump — you're using the tank as a buffer to feed your washer's pump. The pressure washer's built-in pump pulls directly from the tank through a 1"–2" gravity-fed line. The tank just needs to be elevated enough to maintain positive head pressure to the washer's inlet. A ball valve at the tank outlet and a 1.5"–2" suction line are all that's required.
Trailer Selection
The trailer itself matters as much as the tank. Key specs to look for:
- GVWR: Must exceed the total weight of tank + water + pump + frame. A 1,000-gallon full tank needs a trailer rated at minimum 9,000–10,000 lbs GVWR.
- Axle count: 500-gallon setups typically use single-axle trailers. 1,000-gallon loads benefit from tandem axles for stability and tire load distribution.
- Deck material: Steel decking is standard. Treated wood decking will rot under constant water exposure.
- Brake requirement: Most states require brakes on trailers over 3,000 lbs GVWR. A full 500-gallon trailer typically exceeds this threshold.
Buying a Used Tank Trailer
Used water tank trailers are widely available on Craigslist, Facebook Marketplace, and at farm auctions. A well-maintained trailer is a good buy — but there are specific failure points to check before handing over cash.
- Tank interior: Look through the fill lid with a flashlight. Algae, sediment, or biofilm buildup is normal and cleanable. Cracks, crazing, or chalky interior walls indicate UV degradation or chemical contamination.
- Outlet fittings: Stress cracks around tank outlet bulkheads are the #1 failure point on used poly tanks. Run water through the system and watch for weeping around all fittings.
- Trailer frame: Look for rust at weld points, cracks in the tongue, and the condition of coupler, chains, and lights.
- Tires: Sidewall cracking ("dry rot") from UV exposure is common on trailers that sit outside. Budget for tire replacement if the trailer has sat for years.
- Title: Ensure the trailer has a clean title. Agricultural trailers are sometimes operated title-exempt, which complicates resale.
Frequently Asked Questions
A full 500-gallon water tank trailer weighs approximately 4,500–4,800 lbs — water alone is 4,173 lbs, plus the trailer frame (600–900 lbs) and the tank's empty weight (100–160 lbs). Always verify your truck's trailer tow rating and the trailer's GVWR before loading.
In most US states, no CDL is required for agricultural trailers under 26,001 lbs GVWR operated on private property or for farm use. A full 1,000-gallon trailer typically weighs 9,000–10,000 lbs, well under the CDL threshold. However, commercial use (hauling water for hire) may trigger additional licensing requirements — check your state's DOT rules.
Technically yes, but it's not recommended. Vertical tanks have a high center of gravity that creates dangerous sloshing dynamics when the trailer is in motion. Horizontal transport tanks are specifically designed with a low profile and flat bottom cradle sections for secure trailer mounting. Use a horizontal tank.
Use 2"–4" ratchet straps rated above the tank's full weight, routed through the molded cradle sections or tie-down loops on the tank's base. Add rubber matting between the tank and trailer deck to prevent abrasion and movement. For permanent installations, J-bolt tank mounting rings welded to the trailer frame provide the most secure attachment.