Selecting The Right Pressure
Are you under a lot of pressure to figure out
what type of power washer to buy? We can help.
You face a lot of decisions in choosing a
new pressure washer. Don?t be intimidated by all of
the terms and specifications, but recognize what
facts you need to know to make a good business
The most important thing to know is that
your equipment must match the work you intend to
do. If you equipment is too large or powerful, you
have wasted money and you could damage what you
are cleaning. If your equipment is too small, it will
take too long to do the work and you will lose
money. That is the simple truth.
Let?s start by looking at the different
choices you will have to make:
1. Gasoline vs Electric
2. Hot Water vs Cold Water
3. PSI vs GPM vs CU
4. Belt Drive vs Direct vs Gear Driven
5. Portable vs Stationary
6. Wobble vs Axial vs Camshaft Pump
7. Heavyweight vs Lightweight
8. Home Model vs Contractor Model
Gasoline vs Electric: Most pressure
washers are either powered by an electric motor or a
gasoline engine. A few are diesel powered. Electrics
require little maintenance and are very quiet. They
require a source of power nearby (because the cord
length is limited). They can be used indoors without
any problem. You can have electric units with lots of
power, but most electrics are small units designed for
specific jobs, such as mobile detailing or deck
cleaning. Gas units, on the other hand, can be
extremely portable. They are designed for outdoor
use and can be built to deliver tons of cleaning
power. They can be somewhat loud, but your
customers expect to hear some noise while you are
working. Gas-powered machines are used for cleaning
concrete (called ?flat work?), deck cleaning, fleet
work, kitchen hoods and ducts, or any other job that
Hot Water vs Cold: Most pressure
waters are cold-water portables. Cold water, along
with the right cleaners, can do most jobs. Some jobs,
like removing heavy grease or stripping off finishes,
just go better with hot water. Hot water will enable
you to cut about 30% off the time it takes to do ANY
job. This business is all about time, not spending less
on your tools. If you have the right tools, you can
compete with other contractors and get done with
each job in the shortest amount of time. Many new
contractors make the mistake of under-buying their
tools to save money. Most experienced contractors
over-buy their tools and make the difference back in
no time with the added power and features. If all you
are going to do is clean and seal wood, just buy a
cold water machine. If you are washing anything
else, such as houses or hoods or trucks or concrete,
consider hot water. If you already own a cold water
machine and want to have hot water, you can call us
and buy a ?hot box? which will heat the water coming
out of your cold pressure washer.
PSI vs GPM vs CU: First of all, let?s
take any mystery out of the
acronyms. PSI stands for Pounds per Square Inch.
This is the pressure rating of your power washer.
GPM stands for Gallons Per Minute, the flow rate of
your power washer. CU stands for Cleaning Units,
which is PSI multiplied by GPM. All of these terms
refer to the power of your pressure washer.
To clean effectively, a power washer must
provide ?agitation? to
scrub off the dirt and ?flow? to
rinse it away. Think of the pressure (PSI) as the
agitation that is applied to the surface that you are
cleaning and think of the flow (GPM) as the rinsing
force that carries the dirt away.
Homeowner machines tend to run between
2700 PSI. Contractor-grade power washers tend to
run between 3000 and 5000 PSI. More power means
faster work, but more power also means more
potential for surface damage. Wood decks, for
example, are often cleaned at pressure as low as 300
PSI because 3000 PSI will rip the wood to shreds.
Most contractors will settle for 3000 PSI because
that amount of pressure is adequate for most jobs.
Truth is that most contractors would prefer to have
3500 or even 4000 PSI if they could get it.
GPM is much more important to most
than PSI. Since most contractors use cleaning
chemicals to do most of the work (the fastest
method) their job becomes one primarily of rinsing
rather than washing. The cleaners do all of the
cleaning, and the contractor rinses the dirt away.
When you think about that method, you realize that
the more flow you have, the faster the job is rinsed.
Therefore, most experienced contractors recognize
that GPM is more important to them than PSI.
PSI (power) will help you break the chemical
between the cleaning surface and the dirt. Once the
bond is broken, the extra PSI does nothing to speed
up the cleaning time.
The higher the GPM, however, the more
a pressure washer can clean. For example, a 2000-
PSI model with a 2 GPM flow rate might clean
approximately 5-7 square feet per minute. If the
same unit had a 3 GPM flow rate, it might clean 8-10
square feet in the same amount of time.
In this business, contractors sell ?the
The contractor who gets that job done in two hours
might be making $50 per hour. The guy who gets the
same job done in one hour makes $100 per hour.
Which one do you want to be?
Dealers of homeowner machines like to refer
when they show you a power washer. This number is
the result of multiplying the PSI by the GPM. If you
have 3000 PSI and 4 GPM, you have 12000 CUs. For
homeowner machines, this is a good comparison of
the power you are buying. For professionals, CUs
have little meaning. GPM is most important, and PSI
is less important, and the CU formula makes them
both equal. The best solution is to talk to a dealer
who really understands what you are trying to clean
because he will steer you to the right GPM and PSI
for the job.
Belt Drive vs Direct vs Gear Driven:
engines used for power washers all run at around
3450 RPM. In a Direct Drive power washer that pump
is bolted to the engine shaft, so it spins at the same
3450 RPM. In a belt drive unit, the engine is tied to
the pump through pulleys and a belt and the speed
of the pump is reduced to either 1700 RPM or 1400
RPM. In a gear-driven machine, the engine delivers
power to a transmission that in turn spins the pump
at a reduced speed (1700 RPM).
Direct drive power washers transfer the
the engine directly to the pump as well.
The faster pumps of direct-drive machines
spinning so fast that they cannot draw water from a
tank or a lake very well. They tend to work fine when
the water is forced into the machine (like when you
hook it up to a hose from the house).
The slower moving pumps (belt driven or
work less and wear less, so they tend to last many
years longer. They will also pull water to the machine
from a tank, so your power washer shouldn?t ever be
starved for water (a problem that results in
destroying the pump).
Gear driven pumps still transmit the engine
to the pump because everything is hard-bolted
together. However, the pump in a gear-driven model
is running at a similar reduced speed to the belt-
driven models. This kind of power washer has not
popular since it was introduced because there is
obviously one more part to break in the system ? the
Portable vs Stationary: Stationary
are used in car washes, factories, etc. They are
installed in place and never move. Portable power
washers are used by contractors who travel to the
customer to do the work. There is a crossover model
called a skid unit - a stationary machine designed to
be installed on a trailer so that it can be taken to the
customer?s site for the work. The most common
machines for contractors to use are cold water
portables (for small residential work) and hot water
skid units (for large commercial work or high-volume
Wobble vs Axial vs Camshaft Pump:
Since your pump
is the heart of your system, it is critical to
understand what you are buying. Every pump
manufacturer makes several grades of pumps ? Good,
Better, and Best.
The Wobble design requires a piston to push
the pressure in the pump and the pressure of a
spring. This is an inexpensive design to build, but it is
relatively inefficient, too. This is the design found on
most homeowner machines. It is designed to work for
limited hours at a time and very limited hours per
year, which is OK for a homeowner but doubtful for a
contractor who wants to work every day. Wobble
pumps tend to last for around 300 hours before
needing extensive service or replacement.
The Axial design is similar to the wobble
design with a
couple of important differences. Most axial pumps
have larger oil reservoirs and bearings, which allow
them to be used for longer periods of time and more
hours per year. They still are inefficient (like the
wobble) but several lower-priced contractor-grade
machines work fine with the axial design. Axial pumps
tend to last for about 600 hours before needing
The Camshaft design delivers the most
durability of all these designs. It uses connecting
rods on a cam with large bearings like a car engine,
so it runs cooler and lasts longer. It is able to hold up
to continuous use for hours and hours as long as it is
kept cool. Cam pumps tend to run for 1000 hours
before needing service, and tend to last 2000 hours
before needing extensive service or replacement.
Heavyweight vs Lightweight: If you
are buying a
portable power washer, it makes sense to pay
attention to the weight of the unit. After all, you are
the one who is going to lug it all around and move it
into and out of your truck. Aluminum frames can be
fragile, and steel frames can be heavy, so talk to
your dealer about how you are going to transport the
machine. He may be able to steer you to a good
solution for your needs.
Home Model vs Contractor Model:
The final choice for
you to think about is durability. We have already
discussed the difference in pumps, even from the
same pump manufacturer. The cheapest power
washers usually have the cheapest pump, which
won?t hold up well for most contractors. There are
other considerations that you need to think about,
The finish of the machine can be very
important. Powder coating holds up better and lasts
painted frames. Steel frames rust. Aluminum or
stainless doesn?t. Aluminum can be bent, steel is very
rigid. Choices, choices.
For power washers that will be used at
hours per week and sometimes up to 8 hours in a
day, the lower priced machines just won?t last very
long. They come with inadequate parts throughout,
such as the unloaders, pumps, and even the engines.
Just because it says ?Honda?, for example, doesn?t
mean that all Hondas are the same. This is where
Grandpa?s ?you get what you pay for? saying really is
By the way, everybody loves Honda
engines. They hold up very well. Vanguard engines
are built every bit as well and last as long as Hondas,
and seem to deliver more real power per rated
horsepower. That means I measure a little
more "ooomph" from a 16 HP Vanguard than I get
from a 16 HP Honda.
There are a lot of
different pump brands to choose from out there, too.
If someone states a preference when buying a new
pressure washer, Cat is the most specified brand I
hear. My experience is that all of the major brand
pumps are excellent, and I get the most serviceable
use per dollar from General Pump and AR. Other folks
may have other experiences, but we specify General
Pumps for the machines we bring into stock.
So, getting back to discussing value, if you
buy a $900 power washer and you
months use out of it, that purchase cost you $150
per month. If you bought a name brand commercial-
grade machine of the same specifications for $1600
and you got 5 years of use from it, that purchase
cost you $27 per month. Which one is less
Let me relate some of my own experiences.
pressure washer dealer, I see homeowners dragging
in dead machines that are only a few months old
every week. These machines cost more to fix than to
replace, so my ?boneyard? is full of discarded
I recently sold two old pressure washers
that I used
when I was a contractor and didn?t want any more.
They were each 12 years old and each ran like a top.
One had needed only routine maintenance over its
life. The other had to have the pump completely
rebuilt about three years ago. They were both belt-
driven units with AR pumps and Honda engines. I paid
about $1500 for each and sold them for about $300
each. When I added up all of the maintenance costs
and the purchase price and then subtracted what I
got for them when I sold them, those power washers
costs me about $16 per month to own. Is there a
better deal than that anywhere?
If the bottom line for you is how much cash
to fork over right now, consider an alternative. A
reputable dealer can get you into a quality power
washer on a lease or finance contract. In the long
run, you are better off with the better equipment.
You will spend less of your cash today and less over
the life of the machine ? even with the lease or loan
interest added on.