It is the part of the rig that does no cleaning at all, and yet it is often the difference between landing a job and turning it down. A pressure washer tanks setup is the quiet enabler of a serious mobile operation. Without a tank, you are tethered to whatever spigot the client happens to have, hoping it works, hoping the flow is enough, and hoping the homeowner does not mind you dragging a hose across the lawn. With a tank, you arrive self-sufficient and ready, able to work at a job site with no water at all. That freedom is why experienced operators treat the tank as a core piece of equipment, not an accessory.
This guide covers pressure washer tanks in depth. We will explain what they do, the materials and shapes available, how to size one, how tanks integrate with the machine, plumbing and pumps, common configurations, maintenance, and buying advice. By the end, you will know how to choose a tank that turns your pressure washer into a truly mobile, self-contained rig.
What Pressure Washer Tanks Do
A tank stores water on the rig so you can clean without connecting to a client’s supply.
- Provide a water source wherever you can park.
- Buffer demand between a low-flow source and the machine.
- Support soft washing with stored water and chemical mix.
- Make the rig self-contained and professional.
No tank means no water wherever you go. With one, you are free to work almost anywhere.
Why the Tank Matters So Much
- Access: Take jobs at sites with no water supply.
- Independence: No waiting for a client to unlock a spigot.
- Consistency: Reliable water job after job.
- Professionalism: A self-contained rig looks like a real business.
- Flexibility: Pair with a transfer pump to boost supply.
Materials Compared
| Material | Advantages | Notes |
|---|---|---|
| Polyethylene (poly) | Light, affordable, rust-proof | Most common for mobile rigs |
| Fiberglass | Strong and durable | Heavier and costlier |
| Stainless steel | Very durable, professional | Heavy and expensive |
| Aluminum | Light and strong | Can react with some chemicals |
Poly tanks dominate mobile pressure washing because they are light, affordable, and handle the job well.
Shapes and Configurations
- Horizontal tanks: Low profile, stable on trailers.
- Vertical tanks: Tall with a compact footprint.
- Flat or slim tanks: Fit tight trailer and truck spaces.
- Skid-mounted tanks: Designed to sit on a skid with the machine.
- Baffled tanks: Reduce water sloshing during transport.
How to Size a Tank
Size depends on your machine’s flow and how long your jobs run between refills.
| Machine Flow | Approx. Run Time per 100 Gallons |
|---|---|
| 1.5 GPM | Over an hour |
| 2.5 GPM | About 40 minutes |
| 4.0 GPM | About 25 minutes |
| 5.5 GPM | Under 20 minutes |
Divide tank gallons by GPM to estimate run time, then choose a tank that covers your longest jobs without running dry.
Integrating the Tank With the Machine
- Mount securely to the trailer or skid with straps and brackets.
- Position for balance over the axles.
- Add a shutoff valve and outlet fittings.
- Plumb to the machine, with a transfer pump if gravity is insufficient.
- Include a filter to protect the pump.
- Provide a fill point and overflow.
- Manage water movement with baffles or by keeping it full.
Plumbing and Pumps
- Gravity feed: Tank above the machine; simple but limited.
- Transfer pump: Pushes water from the tank to the machine for reliable supply.
- Float tanks: Refill from a source and hold a working level.
- Bulkhead fittings and valves control flow and drainage.
- Filters and strainers protect the pump and nozzles.
Common Configurations
| Setup | Description | Best For |
|---|---|---|
| Gravity tank | Tank feeds machine by gravity | Simple, small setups |
| Tank plus transfer pump | Pump feeds the machine from the tank | Reliable, consistent flow |
| Buffer tank | Stores and stabilizes supply | Low-flow water sources |
| Soft wash tank | Holds water and mix for chemical work | Soft washing rigs |
Maintenance
- Rinse the tank periodically to remove sediment.
- Clean filters and strainers regularly.
- Check fittings and valves for leaks.
- Inspect straps and mounts for security.
- Drain and dry before freezing weather.
- Never let a tank freeze with water inside.
Buying Tips
- Size for your jobs and flow, not just price.
- Consider weight and your trailer’s payload capacity.
- Choose baffled tanks for safer towing.
- Prefer UV-stabilized poly for outdoor use.
- Plan plumbing with valves and filters from the start.
- Match fittings to your pump and machine.
- Buy from a reputable supplier with warranty support.
Frequently Asked Questions
Do I need a water tank for pressure washing?
If you work at sites without a usable water supply, yes. A tank frees you from clients’ spigots and makes your rig self-contained and professional.
What size pressure washer tank should I get?
Size it to your machine’s GPM and your longest jobs. Divide tank gallons by GPM for run time, and choose a tank that avoids running dry mid-job.
What is the best tank material?
Polyethylene is the most popular for mobile rigs because it is light, affordable, and rust-proof. Fiberglass and stainless offer more durability at higher weight and cost.
Do I need a pump with my tank?
Not always. Gravity feed works for lower-flow setups, but a transfer pump provides reliable, consistent supply and is common on commercial rigs.
How do I stop water from sloshing in the tank?
Use a baffled tank or keep it reasonably full. That reduces movement, keeps the trailer stable, and makes towing safer.
Final Thoughts
Pressure washer tanks are the foundation of a self-contained rig. They store the water you need, free you from a client’s spigot, and let you take jobs nearly anywhere.
Size the tank to your flow and jobs, choose a light, durable material, plan the plumbing with valves and filters, and manage water movement for safe towing. Choose and care for the right tank, and your pressure washer becomes a truly mobile, professional operation.