Simpson 4200 PSI Gas Pressure Washer, 4.0 GPM Commercial Power Washer, Cold Water, Honda GX390 Engine, 50′ Hose, Aluminum Series, 49-State Compliant (ALH3228-S)
Original price was: $1,499.00.$1,329.00Current price is: $1,329.00.
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Features & Compatibility
Price: $1,499.00 - $1,329.00
(as of Apr 03, 2026 13:09:29 UTC – Details)
The SIMPSON Aluminum Series pressure washer 4200 PSI at 4.0 GPM is great for construction, equipment upkeep, and facility and fleet maintenance cleaning. With a powerful HONDA GX390 engine, reliable CAT triplex pump, and ultra lightweight aircraft grade aluminum frame, this pressure washer is the optimum blend of maneuverability and performance. The ALH4240 also comes with a 50’ hose, ergonomic spray gun, and 5 Quick Connect nozzles. Designed to meet the rigorous demands of the cleaning professional, the SIMPSON Aluminum Series frame is crafted of 100% aircraft grade aluminum, making it lighter in weight than most steel frame pressure washer designs. Perfect for contractors who specialize in deck cleaning, wood restoration, paint preparation, graffiti removal and all other professional cleaning services. The SIMPSON Aluminum Series designed for optimum performance in the harshest environments. Easy-to-assemble and easy-to-start, the Aluminum Series power washer is great for contractors who specialize in deck cleaning, wood restoration, and all professional services. 10 Year Limited Frame Warranty, 5 Year Limited Pump Warranty, 3 Year Limited Engine Warranty. Includes: Pressure Washer, Hose, Gun, Wand, 5 Quick connect nozzle tips, Detergent siphon tube with filter, Engine Oil, Quick start set up guide, Owner’s manual.
SIMPSON PRESSURE WASHER FOR PROFESSIONALS: The Simpson Aluminum Series gas power washer cleans decks, driveways, siding, fencing, equipment, and graffiti; The cold water machine is great for contractors; 49-State Compliant (Not for sale in California)
ENGINE & PUMP: HONDA GX390 engine starts easily & includes low-oil shutdown; 4200 PSI 4.0 GPM CAT triplex plunger pump includes thermal relief to prevent overheating; Advanced oil seal technology & ceramic coated pistons extend seal life
LONG HOSE REACH: The Simpson Monster series 50′ dual-braided high-pressure hose resists kinks and abrasion; Non-marring polyurethane jacket helps protect finished surfaces; Threaded M22 pump/hose connection
EASY MOBILITY: 13″ premium pneumatic tires roll smoothly over gravel, grass, and curbs; Balanced layout improves transport; Aircraft grade aluminum frame with powder-coated finish is easy to assemble and resists corrosion; 38″ L x 23.5″ W x 29″ H; 133 lb
PRO PRESSURE WASHER ACCESSORIES: Five quick-connect pressure washer tips (0°, 15°, 25°, 40°, and soap nozzle) cover tasks from stripping paint to car cleaning; Professional QC spray gun with safety lock-out and 16″ spray wand included
Kenneth B. –
This thing is a beast!
I read a LOT of reviews here on Amazon and other online resources before deciding to make such a sizable investment in this 4200 PSI/4.0 GPM machine. This is not my first pressure washer, but my third actually. Each time I upgraded in both PSI and gallons per minute. This is my first pressure washer that is categorized as commercial use. Having finally taken the time to put this machine to the test, I can honestly say this thing has more than enough power to satisfy the average homeowner or DIY’er. As I said in the title: this thing is a beast!Mine arrived complete and undamaged. Other reviewers reported scratches and dents but that was not my experience at all. Assembly was quick and easy. My shipment contained a quart of Amsoil synthetic 10W-30 for the engine crankcase but I have seen other reviewers that got their oil in a plastic pouch.Once assembled, the crankcase filled with the supplied oil, and the fuel tank filled 1/2 way, I hooked up the garden hose and bled the air out for 30+ seconds as recommended. Set the throttle to half-way and closed the choke and gave the starter a quick pull and it fired right up on the first attempt. After allowing the engine to run at partial throttle with the trigger open to keep the water flowing and the pump cooled for a few minutes, I increased the engine speed to approximately 3/4 and started cleaning the concrete patio as my first project with this unit. The pressure even at less than wide open on the Honda GX390 was more than enough to get the accumulated grime blasted off effortlessly. Next up, I connected my 15” surface cleaner which really sped up the process. The 4240 pressure and water flow are a perfect match for the Karcher 15” surface cleaner.With all of the positive attributes of this machine, there is one thing that I feel is a negative: the hose. It’s more than long enough for most jobs but the stiffness makes moving around with it a real challenge. Given the higher than average PSI capabilities of the ALH-4240 it’s not surprising that the pressure hose is more on the stiff side, but as others have commented, it would be a good idea to upgrade to a better hose. Honestly, at this price point, a better quality hose should come with it.Overall, the ALH-4240 is a great pressure washer that has all of the power that the average person could want for DIY use. The high PSI and GPM make short work out of even the toughest cleaning projects. Time will tell if it lives up to the Simpson advertised claims of dependability and reliability.
MMADD –
Honda + CAT pumps = Quality
I’d like to start out by saying I own and operate a power washing company and this is my main work horse every day. I’ve owned the machine for a full year now so I figured I’d get Amazon my review.I’ve used this machine for over 6-700 hours in 100 degree heat to down into the 40s. It has never given me one hiccup or issue. I’ve changed the pump oil 3 times and the engine oil twice. I gave it a new Denso spark plug just because I was doing the maintenance on it. Pulled spark plug could have easily gone wagly longer. Machine starts on one pull every time. I do recommend the use of non ethanol gasoline and your carborator will never give you a problem gumming up. Do the maintenance!Honda delivers and excellent product with the GX390. I’ve used them for years. CAT pumps are top of the line and this little pump proves its worth every day.There are some cons, not with the machine but with the frame. The rubber feet that come on the front to support the machine and dampen vibration completely left chat maybe a week into using it and I leave the machine on the truck when it’s in use soni had to improvise with some rubber pads so it wont vibrate a hole into the composite truck bed. The delivery people (UPS) delivered it upside down, thankfully the machine had no issues. Frame was bent up pretty badly to the point where the detachable handle didn’t fit, I had to force it on and now it’s stuck and the wheel was severely crooked rubbing on the side of the frame. I had to kick that like a mule to straighten it to the point where the rub is minor now. I’m not driving the thing cross country so this doesn’t bother me at all. They did not pad the machine in the box barely at all. I believe they could do a lot better there. I looked past it and the machine works flawlesslyThe accessories that come with the machine were mostly junk. I always throw the gun in a box because they always fall apart after a month or so. The hose lasted a long time.I do not use the on board injector because my chemicals are not good for them so I always use my own downstream injector.Never fails with these machines that the exhaust housings rust out on them and usually fall apart after a couple years. They make all the parts for this machine still thankfully.
Professor –
Product arrived damaged
Unfortunately, I am unable to review the pressure washer because it arrived damaged. Consider this review to reflect packaging and shipping, and not the actual pressure washer.I have uploaded images, but to summarize, the pressure washer arrived with the box completely gone, the handle support frame on the left side was bent, the muffler was damaged, and the handle itself was damaged. Additionally, the box with the assembly parts, oil, etc. was, well… let’s just say it was a hot mess. The picture of the box says it all.As you may have read in the reviews for this product, there are a number of buyers who have indicated that their pressure washer arrived damaged. If you decide to purchase this product, please check the condition of the product before you actually use it.When the replacement pressure washer arrives, I will review it.Joe
Jarred Laughlin –
Superior quality
Powerful machine! Great quality.
Belal Moustaph –