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Question DetailsAsked on 2/26/2014

What pressure power washer should I buy for a metal shed, deck and patio cleaning? Is 1500psi strong enough?

I want to remove mildew from a white metal shed and clean a concrete patio, wrought iron furniture and a wood deck with painted railing. I'm not necessarily attempting to remove paint but if the pressure is sufficient to remove loose paint, that's fine.

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6 Answers


1,500 psi is more than enough and arguably, too much.

I would look into a solution of bleach or TSP. It will probably take off the mildew quicker and with less potential damage to the substrate.

Answered 6 years ago by WoWHomeSolutions


1) 1500-2000 is the right range for this - will strip paint if head right up close, but is not high enough to cut or gouge wood or concrete at normal use distance. 1000 is undersize for patio and concrete washing, and 3000+ is overkill for homeowner use. The normal small upright type like this -

work fine for homeowner use, though it does get old if you try to do an entire driveway with it more often than once every year or two. 1.5 gpm is good for occasional homeowner use - if you intend to routinely do entire outside of house or full driveway, or to use it to clean sand and gravel off the lawn after winter snowplow berming on your lawn, then I would recommend a 2.5-3 gpm size.

2) One tough decision is whether to get electric or gas powered - depends on whether you think you will ever need it to clean a boat at a slip, at a cabin, etc. and whether you have power, or a generator, there.

3) One recommendation - get one with automatic overpressure shutoff or bypass - prevents it from overheating the pump and ruining the unit if it sits for more than about 10-15 seconds without water flowing through it. Most people do not realize this, but the pump sitting there compressing water at 1000+ psi builds up heat VERY quickly, and more than 10-15 seconds without water flowing through the pump WILL destroy it, for a repair cost at least $75-100 - so you need an automatic bypass or shutoff device on it, PARTICULARLY if being used on a ladder or roof where it may take longer than that just to get down and to the unit.

4) Also consider how much hose you need - it is VERY expensive for extension hose, so if you anticipate needing enough to reach up on the roof or up a 20-25' ladder, it is generally much cheaper to buy a unit with a longer hose than to buy a smaller unit plus extra hose later. Also, many of the smaller units do not use standard high pressure hose fittings, so finding hose to extend them can be near impossible.

5) Also make sure you get both jet and fan nozzle tip, or adjustable one, because you will need both. Again, many smaller units do not take standard tip thread, so be sure you get all the accessories you need with the unit so you do not have to run all over town trying to find tips or hoses or adapters that fit.

6) You mentioned deck and shed cleaning - bear in mind the pressure just makes it go faster - it is the mold and mildew remover or the detergent soaked into the dirt that removes the dirt or mildew. Concrete and patios the pressure itself does help with the cleaning by getting down into the openings and crevices, particularly nice for removing moss.

7) One other thought - it is very nice to have a detergent/cleaner attachment for it, so you can use it to spray on the deetergent or cleaner, let it sit, then pressure wash it off. However, do NOT get the kind where the cleaner goes through the pump - tears it up, and causes corrosion sitting there. You should get the kind where there is a venturi fitting downstream of the the pump (on the pressure hose side) that sucks the cleaner in through a flexible tube without passing through the pump.

8) On the use side - read instruction carefully on startup and shutdown, NEVER turn off or disconnect water supply hose before unplugging or shutting down the pump, and never let freeze, as there will commonly be water left in the pump itself.

Answered 6 years ago by LCD



I would recommend using Angie's List to find a licensed and insured service company to do the job for you. It does not make much sense to spend several hundreds of dollars to do a job that will only have to be repeated once a year if done correctly with commercial equipment the first time. And if you injure yourself or others trying to operate gas powered equipment, well it is safe to say it will be very costly in the long run. As a business owner at JB Power Wash, we help people everyday with the simple chores of power washing projects.

And for your information, PSI is not what determines the cleaning factor of a pressure washer, it is the gallons per minute that matters. Yes, more is better but not offered with small psi machines. Proper detergents and the knowledge of mixing chemicals is manditory to get any pressure washing job done correctly.


Owner at JB Power Wash


Answered 6 years ago by JBPowerWash


1) I hate to say it, but I think James at JB Powerwash is about all washed up - pun intended, and I take his input as an example, in my opinion, of the kind of statements that should make you think twice about hiring a contractor.

2) Aside from the fact that the proper detergent or cleaning solvent effectively does most of the work in loosening dirt for removal unless you are using such high pressure that you risk damaging the surface, the factor that makes a pressure washer work is PRESSURE (psi), not the flow rate, which is measured in GPM (gallons per minute). Without adequate pressure, you get nothing. For instance, you can blow a couple psi out your mouth - but at that pressure, you will not clean anything but totally loose dirt, regardless of how many gpm you put on it. Think of a garden hose - a couple to maybe ten psi where the stream hits the surface - increase that to a fire hydrant at same low pressure, no improvement, just a bigger puddle. Turn the nozzle down on a firehose connected to the hydrant so it is producing fullpressure of maybe 150 psi, and it knocks you on your can - but the flow rate will go way down if you do that. It is the PRESSURE that does the work- more flow (gpm) just means you can hit a larger surface area with the same pressure, making the work go faster, and greater water will wash the piled up debris away on the ground fasterI grant.

3) I will not go into pressures in detail, but generally takes around 100-300 psi to blast built-up caked on dirt like under a car, 1000-1500 psi is needed to effectively remove peeling paint or peeling driveway sealer or start damaging the surface of paints or sealants, 2-4,000 to strip paint off wood or concrete though over about 1000-1500 can also gouge wood and cut shingles which is why using pressure washing to strip paint or wash a roof is a dubious practice in unprofessional hands and commonly causes problems, 5-10,000 psi range to effectively strip well-adhered paint off metal (though there are a lot of car owners that will testify to being able to damage it pretty good at 1500-3000 psi at very close range), and so on all the way up to 5-10,000 psi range to cut most plastics and wood and for concrete surface prep or light cutting, 10-30,000 psi for normal concrete and stone cutting and demolition, and on up to 30-90,000 psi to cut very hard stones like granite and metals. Of course, above about 4,000 psi you are talking industrial size machines, and above about 20,000 psi you are generally talking cutters, not cleaners. In each case, the above pressures are those needed to work effectively - you can do it at somewhat lower pressures, but tediously slow.

4) Also, the "cleaning factor" he talked about is a meaningless number created by the industry to make you think it means something and so they can put a big number on their machines, but is about as meaningful as the Body Mass Index which pays zero attention to age or type of bone structure or whether you are a desk jockey or in the Special Forces or a weighlifter. It is simply the pressure (psi) multiplied by the water flow rate (gpm) - the product of the two and equally affected by changes in either, NOT only by the gpm as stated. A higher flow rate at the same pressure only increases the surface area that can be exposed to that pressure at one time and hence the productivity, not the actual efficiency of cleaning, except with respect to cleaning flat surfaces where more runoff water flow does move the debris away from the work area a bit better - just like full flow through a hose washes the drive faster than at half flow. However, the "cleaning factor" is meaningless. Example - a 2000 psi machine at 1.8 gpm say, a normal sized small highly portable homeowner electric machine like you can get at most box stores, would have a "cleaning factor" of 3600 and has enough power to strip skin off you. I could also give you an 1800 gpm pump - equivalent to about the flow the largest fire trucks can deliver roughly, delivered at 2 psi or about as high a lung pressure as any person has been recorded producing, and it would have the same cleaning factor - even though it would have less pressure, and hence less cleaning power, than the water pouring out of your bathtub spout. Would be equivalent force to standing in the ocean as a 1 inch high wave passes by. Another way of looking at it is consider an open fire hydrant - might put out about that flow when broken off - kids can easily play in it because the pressure is low - maybe 5-10 psi after the initial surge, yet hook up a fire hose to a hydrant and at the 100-150 psi or so typical pressure, even though the flow will drop off a lot with the smaller discharge size, it will certainly clean your clock in a hurry.

5) So much for the physics lesson for the day.

Answered 6 years ago by LCD


I would suggest a professional, simply because they know what they are doing. Trying to wand your patio is a lot harder than most realize. You can damage the concrete and/or leave striping. Which looks worse in the end and you've wasted most of a day/weekend. A professional can clean an average patio in 30mins or less, they leave no striping and won't damage the surface.

For the mold and mildew, again, a professional can complete the work in much less time. But if you prefer to do it yourself, you can purchase a product from Scot's that attaches to your hose. A soft brush will knock off the loose paint.

If you are not experienced with using your home machine, there is a good chance of ruining something. Often brute force isn't needed. You can damage the wood, strip paint you didn't intend to strip. A professional knows when to use pressure and when to use a soft wash.


Answered 4 years ago by skbloom


Flow IS more important than PSI in the pressure washing field. Mostly in terms of SPEED. The pressure is the aggitator and dirt lifter while flow is what takes the dirt away. The more water that goes across a surface, the more dirt it can take with it. Add in quality chemicals, and high flow will absolutley out clean a lower flow unit.

I tend to agree with the advice of just hiring this service out as a Professional is quite often more efficient and costs less than trying to DIY. Our more expensive professional grade washers are actually, in the long run, less expensive than the cheap big box store units. Last longer and with fewer upkeep costs. Take advantage of this. Faster = less time. How much is your time worth?

That, said 1500 psi is quite sufficent for what you are trying to do. In fact we don't even go over 150psi on most house washes. Detergent does bulk of work and high flow speeds up chem application and rinse.

This is HIGH FLOW in action at only 2500psi but 8gpm...

This is LOW Pressure and HIGH FLOW cleaning with detergents....

Please take your advice for pressure washing ONLY contractors. Handyman types simply do not have the depth of professional pressure washing contractors do.


Answered 4 years ago by jmkreisle

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