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The Simpson ALH4240 is a commercial-grade gas pressure washer featuring a robust Honda GX390 engine paired with a maintenance-free CAT triplex plunger pump, delivering 4200 PSI at 4.0 GPM. Built on a corrosion-resistant aircraft-grade aluminum frame with premium pneumatic tires, it offers superior portability and durability. Equipped with a 50-foot steel-braided hose and 5 quick-connect nozzles, it’s engineered for professional contractors tackling deck cleaning, wood restoration, graffiti removal, and more. Supported by extensive warranties, this powerhouse blends performance and reliability for demanding cleaning tasks.

















| ASIN | B00U77BYF6 |
| Best Sellers Rank | #120,112 in Patio, Lawn & Garden ( See Top 100 in Patio, Lawn & Garden ) #612 in Pressure Washers |
| Brand | SIMPSON |
| Color | Red |
| Customer Reviews | 4.0 4.0 out of 5 stars (477) |
| Global Trade Identification Number | 00879399001345 |
| Hose Length | 50 Inches |
| Is Discontinued By Manufacturer | No |
| Item Weight | 124 pounds |
| Item model number | ALH4240 |
| Manufacturer | SIMPSON |
| Maximum Flow Rate | 4 Gallons Per Minute |
| Power Source | Gasoline |
| Product Dimensions | 38"L x 23.5"W x 29"H |
| Tank Volume | 2.5 Gallons |
| UPC | 879399001345 |
| Wand Length | 31 Inches |
K**.
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.
M**D
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 flawlessly The 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.
G**N
I do not recommend this machine or the company that makes them.
When I received it, it came with a few bumps and I tried to return it but in the end I didn't do it for work reasons, 6 months have passed and suddenly the water pump was used. 3 months ago I sent the guarantee that they provide by phone. The guarantor just says that they still do. I do not receive the answers from the Simpson company I really do not recommend this type of brands, you have to play it safe like Sthil. I make this new review of the state of the machine and the technician. It's been 7 months and Jason, representative of the simpson company, tells me that they will not repair the water pump and blames me for excessive use (it was only tested once, never used at work) and it will not be repaired. I lost jobs, money in advertising, billboards.Update 2023, after having spent 7 months in the repair shop today they called me to return what was left of the washing machine. They did not return it and I had to pay the shipping costs for it. The guarantee did not take care of the bomb, from the guarantee they exposed that it was due to excessive use but it was never used when it exploded. It only remains to say that this machine is rubbish and it is throwing money at them, the company that manufactures them is not interested in the product once it is sold. But I thank Amazon because the heavy goods reps helped find a way out for my . Thanks Amazon! 👍🏻
B**H
Trustpilot
2 days ago
1 month ago