Pressure Washing Tanks

What a buffer tank does, and why you need one

A pressure washer pulls more water than most spigots can give it. An 8 GPM machine on a hose bib flowing 5 or 6 GPM will starve, cavitate and burn up a pump. The buffer tank sits between the customer's water and your pump so the machine always has a full column of water to draw from, and it lets you keep washing while the tank refills from the spigot. Every rig we build carries one, and it is the first thing we add to a customer's truck when they show up with a machine bolted to a bare bed.

We ran our own washing company for over a decade before we started building, and tanks were where we saw the most avoidable failures: thin walls that bulged and split, cheap straps that let a full tank walk across the bed, and drum tanks that took up half a truck to hold 55 gallons. That is why our tanks are about twice the wall thickness of typical builder tanks, and why we sell the straps and plumbing kits alongside them.

Which tank for which rig

Sizing a buffer tank to your machine

The rule of thumb: 100 gallons for one machine up to 8 GPM, 200 gallons for two machines or hot water, more if you regularly work where there is no spigot. The math is your machine's draw minus the spigot's flow, times how long you run the gun between refills. A 5.5 GPM machine on a 6 GPM spigot can run all day on 50 gallons; an 8 GPM machine on that same spigot loses 2 gallons a minute and needs 100 gallons to get through a house wash without waiting. Two 8 GPM machines need 200 gallons and, ideally, two supply hoses feeding the tank. We wrote more about matching machine size to the work in 4 GPM vs. 5.5 GPM vs. 8 GPM.

Slim vertical vs. drum vs. detail tanks

Slim vertical tanks are 12 to 13 inches deep and stand up against the cab or headboard, so a 100-gallon tank uses a foot of bed length instead of three. That is why every skid we build uses them. Drum-style tanks are cheap but waste space and roll. Low-profile detail tanks are for rigs where load height matters more than bed length, such as detailing setups and pure water systems.

Water weight and payload

Water is 8.3 pounds per gallon. A full 100-gallon tank is 830 pounds plus the tank; a full 200 is over 1,600. Check your truck's payload sticker before you buy the bigger tank, and never run a tank without straps rated for the full weight. Our heavy-duty tank straps are the same ones we bolt onto every build.

Plumbing a buffer tank

You need a bulkhead fitting in the bottom of the tank, a float valve in the top to shut the fill off, a supply hose in and a suction line out to the pump, and ideally a shutoff and a filter on the outlet. Our buffer tank plumbing kit has everything sized for 4 to 10 GPM machines so you are not guessing at fittings. Use bulkheads and a high-flow Hudson float valve on the fill; a standard float will not keep up with an 8 GPM machine. Tank lids, cap plugs and Uniseals for adding ports are on this page too.

Chemical and soap tanks

Sodium hypochlorite goes in its own tank, never in the buffer. The 55 Gallon Vertical and V1 100 are rated for SH storage and are what we use for bleach on our soft wash builds; the 7 Gallon Soap Tank holds surfactant next to the mixer. Keep chemical tanks strapped just as hard as water tanks; bleach is heavier than water.

Shipping

Tanks ship by freight and do not qualify for free shipping. Call 503-403-6185 or email orders@expertpowerwash.com with your address and whether it is residential (lift gate) or commercial (dock or forklift) for a quote, or pick up at 13896 S Fir St Suite B, Oregon City, OR, Monday through Thursday, 8am to 4pm. If you are building a whole rig, book a discovery call and we will spec the tank with everything else.

Further reading

• Pressure washing skids and truck setups
• How to install a bulkhead fitting in a water tank
• How a soft wash mixing system works