Pick the kit that matches your chassis GVWR (2K kit needs 26,001+ lb GVWR; 4K kit needs Class 8 tandem). Match pump direction to your transmission's PTO output direction (CW or CCW). Plan for a subframe — never direct-mount a loaded tank to chassis rails. Then spec the spray pattern to your duty cycle. The two SP turnkey kits cover 90% of common builds.
Step 1: GVWR check — the question that comes before all others
Water weighs 8.34 lb/gal. The math from there:
- 2,000 gallons = ~16,700 lb of water alone. Add ~3,500-5,000 lb of tank + pump + plumbing + spray hardware + subframe. Total payload from the build = ~20,000-22,000 lb on top of the truck itself.
- 4,000 gallons = ~33,400 lb of water alone. Add ~5,000-7,500 lb of build. Total payload = ~38,000-41,000 lb.
Look up your chassis's GVWR on the door-jamb sticker. Subtract the curb weight. What's left is your usable payload — and that has to cover the entire build plus the driver plus any fuel and DEF you're carrying.
| Chassis class | Typical GVWR | Fits 2K kit? | Fits 4K kit? |
|---|---|---|---|
| Class 5 (under 19,500 lb GVWR) | 16-19k | No | No |
| Class 6 (19,500-26,000 lb GVWR) | 19.5-26k | Borderline — only the heaviest Class 6 builds | No |
| Class 7 (26,001-33,000 lb GVWR) | 26-33k | Yes — the standard 2K platform | No |
| Class 8 single-axle (33,001-46,000 lb GVWR) | 33-46k | Yes — over-spec but fine | Borderline |
| Class 8 tandem-axle (46,001+ lb GVWR) | 50-66k+ | Yes | Yes — the standard 4K platform |
Hard rule: never put a build on a chassis that will be over GVWR when loaded. Over-GVWR operation is a DOT violation, kills your brake/tire margins, and exposes the operator to insurance and liability problems in any incident. If your chassis GVWR is borderline, size down the tank.
Step 2: Pump direction — the question that catches first-time builders
The pump is driven off the chassis transmission's PTO (power take-off). The PTO output shaft rotates in one direction — either clockwise or counter-clockwise depending on the transmission. The pump impeller has to spin in the same direction or it cavitates and won't move water.
For Allison RDS automatics (the most common transmission on water-truck duty), PTO output is typically clockwise — you want a B3Z-S clockwise pump. For manual transmissions and some other PTO configurations, the rotation may be counter-clockwise — you want a B3Z-S counter-clockwise pump.
How to check before you order: pull the OEM service manual for your specific transmission + PTO part number. The rotation direction is in the PTO spec section. If you're not sure, call us with the transmission model + PTO part number on the side cover — we'll cross-reference and confirm before you put money down on the wrong pump.
If you do order the wrong direction, the impeller in the B3Z-S can be swapped to the opposite-rotation casting (we stock both), but you'll be paying for the swap and the downtime. Better to confirm first.
Step 3: Mounting — the subframe matters more than people think
A loaded water-truck tank is a heavy, sloshing, dynamic load. Direct tank-to-chassis mounting (the tank sitting on the frame rails with bolt-through brackets) point-loads the chassis at the bracket locations and stresses the frame rails under vibration. Over time — especially on rough sites — this can crack frame rails or loosen brackets.
The right approach is a subframe: a welded or bolt-on steel structure that sits between the tank and the chassis rails, distributing the tank load across the full length of the rails rather than point-loading specific spots. The subframe also gives you somewhere clean to mount the pump, the plumbing, the valve manifolds, and the cab-control air lines.
Our turnkey kits include the subframe and mounting hardware. If you're ordering parts piecemeal, budget a subframe into your build — don't skip it.
Step 4: Spray pattern — match the duty cycle, not the spec sheet
The standard spray pattern for a working water truck:
- Rear spray bar — for following-the-truck dust control as you drive over a site.
- Two side-spray heads — for wider coverage and edge-of-road work. Typically duck-bill side spray heads or air-to-close mini spray heads.
- One water cannon (optional) — for high-throughput point work, fire suppression, and tall-stockpile dust control. Electric remote-controlled cannons with 1,250 GPM throughput are the modern standard.
- In-cab pneumatic control panel — switches each spray zone from the driver's seat instead of stopping to operate valves manually. Use the 5-switch panel.
Duty-cycle-driven variations:
- Heavy compaction / mining haul roads: add a second cannon or larger spray heads. Plan for shorter time between refills.
- Light street-wash / municipal: rear bar alone is often enough. Skip cannons.
- Landscape / event work: side sprays + rear bar at lower flow rates. Cannon optional.
Step 5: Which SP kit fits your build
For most builders, one of our two turnkey kits is the right answer:
| Kit | For | Includes |
|---|---|---|
| SP-BUILD-KIT-2K | Class 6-7 chassis · 2,000-gal builds · landscape / municipal / small construction | 2,000-gal cylinder or teardrop tank, B3Z-S mech-seal pump, 3-inch plumbing, rear bar + side sprays, in-cab 5-switch panel, subframe, mounting hardware |
| SP-BUILD-KIT-4K | Class 8 tandem chassis · 4,000-gal builds · mining / heavy construction / municipal high-throughput | 4,000-gal 3-compartment baffled tank, B3Z-S mech-seal pump, 4-inch plumbing, rear bar + side sprays + provision for water cannon, in-cab 5-switch panel, subframe, mounting hardware |
Both kits ship from our Phoenix yard. Both are field-proven on the same chassis families we build for Superior Equipment's sale-ready water trucks — this is the same build pattern, just sold as a kit so you can install on your own chassis.
Common pitfalls we see
- Pump direction wrong. Most common ordering mistake. Cross-check the PTO direction before paying.
- Chassis under GVWR. "It looks big enough" is not a GVWR analysis. Check the door-jamb.
- Skipping the subframe. Saves money up front, costs frame rails 2 years later.
- Wrong plumbing size for the pump. Mismatched plumbing chokes flow. 3-inch pump = 3-inch plumbing, not 2.5-inch.
- No cab control panel. Manual ball-valve operation from the truck side is fine for a stationary site, miserable for a working driver.
- Cannon without electrical provision. Electric cannons need 12V/30A circuit. Plan it during the build, not after.
Frequently asked questions
Can I install a 2,000-gallon water truck kit on a Class 6 chassis?
Yes, if the chassis has the GVWR headroom. Water at 8.34 lb/gal means 2,000 gallons is ~16,700 lb of water alone. Add ~3,500-5,000 lb of tank + pump + plumbing + spray hardware. Your chassis GVWR needs to be at least 25,000-26,000 lb to support a 2K build with a normal driver. Class 6 chassis with GVWR of 26,001+ lb (often M2 106) work. Lower-GVWR Class 6 trucks do not.
How do I know if my chassis needs a CW or CCW pump?
It depends on the PTO direction of your transmission. Look up your specific transmission's PTO output rotation in the OEM service manual — Allison RDS automatics typically have CW PTO output, manual transmissions vary. Pump direction must match PTO direction or you'll cavitate. If you order the wrong direction, the impeller spins backward and the pump pushes air instead of water. We stock both B3Z-S CW and CCW mech-seal pumps at our Phoenix yard.
What if my chassis isn't a standard Class 6-7 build?
Heavier chassis (Class 8) work fine for 2K kits — you have payload headroom to spare. Lighter chassis (Class 5 and below) don't have the GVWR to carry 16,700+ lb of water safely. Custom oversize tank installs on light-duty chassis are not recommended — the truck will be over GVWR loaded, which is a DOT violation and an insurance/liability problem if it's involved in a collision.
Do I need to add a subframe?
Often yes. The tank-to-chassis interface should distribute load across the frame rails rather than point-loading specific spots. A welded or bolt-on subframe with proper mounting brackets is the right approach. Direct tank-to-chassis mounting without a subframe can crack the frame rails over time, especially under loaded vibration on rough sites. We install subframes as part of every kit installation at our Phoenix yard.
What spray configuration should I choose?
Depends on your duty cycle. For typical jobsite dust control: rear spray bar + 2 side-spray heads + 1 water cannon is the standard pattern. Heavy compaction work needs higher flow and more spray heads. Light street wash needs less — sometimes just a rear bar. Cannon-equipped trucks add a remote-control or in-cab pneumatic control for the cannon. Tell us your duty cycle and we'll spec the spray pattern.
What's the difference between a turnkey kit and ordering parts piecemeal?
A turnkey kit includes the tank, pump, drive kit, plumbing, valves, spray heads, hose, cab controls, and the mounting hardware — everything you need to convert a chassis into a working water truck. Piecemeal ordering means you specify each component yourself; you can save 5-10% on the part costs but you're responsible for compatibility (pump direction matches PTO, plumbing sizes match pump output, spray heads match plumbing). Most first-time builders save real time and headaches by ordering a turnkey kit. Repeat builders often go piecemeal because they've solved the compatibility math already.
Not sure which kit fits your chassis? Call us before you order.
We'll walk the chassis GVWR + transmission PTO direction + your duty cycle and recommend the right kit + spray pattern. 5 minutes on the phone beats a wrong-part order.
Call (602) 437-3980 See build kits →Phoenix, AZ · Same-day yard pickup · Net-30 fleet accounts available