Pressure Washing PSI question

November 10, 2014 7:19 AM

I need to buy a pressure washer to clean my concrete driveway, which is somewhat blackened with mildew. I don't want to break the bank, but I'm having trouble figuring out what the minimum PSI I can use is. Does anyone have personal experience in this?

The Home Depot guidance says that I need at least 2000psi to clean a concrete deck. Unfortunately, the price climbs quite a bit when you get past the 1700-1800psi electric models.

I also saw a "turbo nozzle" in the store which claimed that a 1700psi model with a turbo nozzle would be suitable for cleaning a deck, whereas a 1700psi on its own wouldn't be suitable for that.

Trying to make heads of tails -- do I really need to spend $350 on a machine if I want to be able to clean some blackish mildew off concrete?

posted by So You're Saying These Are Pants? to Home & Garden (14 answers total)

Does your Home Depot rent equipment? My local one has a bunch of models to choose from for rent. Great idea if you don't want to shell out for a powerful one or store it.
posted by cecic at 7:33 AM on November 10, 2014 [3 favorites]

Before getting a machine, I would try plain old bleach. You can get a hose attachment that will spray a dilute solution. Ten percent should do it. No need to scrub or rinse, just spray it and let it sit there. After a few rainy days, the stuff should be gone. I do this on my roof which gets black mildew streaks from bird poop. It takes 2-3 weeks, then it's gone.
posted by beagle at 7:39 AM on November 10, 2014 [2 favorites]

We bought an electric pressure washer from Costco that works at 1700 psi and I've recently been using it to clean mildew off concrete successfully. It has a turbo nozzle but that didn't seem to make much difference. Our electric washer outputs a smaller amount of water than a friend's gas motor washer, so the jet is narrower and cleaning takes longer with ours, but it works fine.
posted by anadem at 7:42 AM on November 10, 2014

If all you're going to be using it for is to pressure wash the driveway once a year do not get a gas model. Using a small gas engine once a year is about the worst thing you can do with it, don't expect it to start a year later.

As beagle suggests, consider renting a gas washer for the day.
posted by Runes at 7:46 AM on November 10, 2014 [2 favorites]

Renting is the way to go. Check your local yellow pages (or the internet) to find a tool rental place and you can probably get a serious pressure washer for $50 to $100 per day. Ask the clerk at the rental store, they can guide you to the right tool for the job.

For example you can get a 3000 psi washer here for $83 CAD per day.
posted by Vindaloo at 7:54 AM on November 10, 2014 [1 favorite]

I've used this 1700psi set which clears crud from paving very effectively, if a little slowly due to the small working area.
It has a pulsing, rotating nozzle that might be the key, the standard nozzle isn't as good.
posted by paulash at 8:12 AM on November 10, 2014

Rent or borrow.

You don't need one 2000 psi, but you need higher than a simple nozzle attachment. You can use bleach but may have some downstream issues, especially if your storm sewers empty into canals or other open water systems.

Mine is about $100 (electric) and 1500 psi. It's a little slower than I expect 2000 would be, but it gets done.
posted by Buttons Bellbottom at 8:12 AM on November 10, 2014 [1 favorite]

Before getting a machine, I would try plain old bleach. You can get a hose attachment that will spray a dilute solution. Ten percent should do it. No need to scrub or rinse, just spray it and let it sit there. After a few rainy days, the stuff should be gone.

In my experience this is not true with crud that's been pressed in, or has picked up other crud. For an upstairs vinyl deck I have to spray with some bleach & dish soap and then later do a light pressure wash. The bleach alone will make the crud less dark & scary but it's still there and just comes right back shortly (possibly because there's still a layer of material for new growth?)

We have an electric washer in the 2000 category and what I'd tell you is that it's fine.... and slow. It'll clean anything perfectly with a stripe width of 2". So if you or a family member have the time to creep along the decking, cheap works fine. I put on some ear protection over earbuds and it's a few hours of podcast time.

If this is really just a one-off task, yes, renting is way better. Or possibly better yet, put an ad on craigslist for someone who already has a pressure washer and offer a flat rate to do the job. Someone with a gas powered supermachine might be delighted to offset $60 worth of their expensive purchase.
posted by phearlez at 8:16 AM on November 10, 2014 [2 favorites]

I recently purchased this one from Lowes. It works great and I think it will do everything you need.
posted by humboldt32 at 9:23 AM on November 10, 2014

I have the exact washer that humboldt32 referenced, and it works like a charm. Have had it for about 3 years now, and it's still going strong with pretty regular usage.
posted by PlantGoddess at 10:12 AM on November 10, 2014

Response by poster: Thanks for the suggestions!

There are other reasons why renting is tough, so I just wanted some confirmation that buying something less than the recommended 2000+psi could still work. Sounds like it might, so I'll give it a shot and report back. I appreciate all the responses.
posted by So You're Saying These Are Pants? at 10:21 AM on November 10, 2014

As an alternative to bleach, I was going to suggest a product called Wet&Forget, which I have used successfully on mildew on the back side of my house, but the MSDS says don't let it get into storm drains, etc. So, it would not be a good choice for a driveway.
posted by Kirth Gerson at 10:40 AM on November 10, 2014

The MSDS is referring to a large spill, not normal use. So don't pour the bottle into a storm drain. But you can spray it on your driveway.
posted by ryanrs at 12:12 AM on November 11, 2014

Response by poster: Yep, for normal pavement cleaning, the 1700psi (with the fancy "turbo" nozzle) worked like a charm. There were a couple of more serious grease spots that I couldn't clean, though.

Thanks all.
posted by So You're Saying These Are Pants? at 10:01 AM on November 12, 2014