Have questions about power washing patio

I have a customer with 3 patios and steps that he wants me to power wash for him, problems are a lot of dirt, mold mildew and the steps are soft limestone as he tried with to power wash the steps before by using just the wand with the wrong tip and cut groves in the soft limestone. What is the best way to clean these? Cold power washer or Hot ? What chemicals ? Surface cleaner ? The patios themselves are just concrete.
A Clear View Window Cleaning
Massillon Ohio

You should be fine with the limestone steps with a 40 degree fan spray tip. Just keep the tip far enough from the limestone so you’re not blasting it. With the right chemicals, like bleach for the mold, you won’t need a lot of pressure.

No surface cleaner for the limestone, but definitely for the concrete patio. Hot or cold water shouldn’t really matter on this job, if the areas just moldy and surface dirt, you’d probably be fine with just cold water, save the diesel.

Thanks for your help on this cleaning of the patios, if I can get these cleaned without any damage it will open many doors for me from this customer .
Thanks again
John Birkbeck
A Clear View Window Cleaning

Normally I use the 40 degree tip with a 4000 psi pressure washer with no chemicals, and I have had no problems at all. and you can sell the green angle to your customer.

Even with the mold and mildew John noted?

I would think using 12% in a pump up sprayer (allowing dwell time) of about 10 mins along with a 40 tip would do the trick nicely.

Of course you’d want to make it a point to water down any greenery prior too,plants shrubs etc.and after pressure washing the area give another watering down to any plant life to avoid extended contact of the chemical.

Depending on the length of time the mold has been there you could just pressure wash it but…the stubborn area’s might entice you to want to hammer down thus…causing damage with such a soft substrate.

Straight 12% is a bit much in my opinion. Roof cleaners who deal with heavy mold and moss don’t even use 12% at full strength. A gallon of house hold bleach to 3 gallons of water would be plenty strong enough. Use a deck brush to scrub and you could probably rinse the steps clean with a garden hose. This may put the homeowner at ease, knowing that you won’t even use the pressure washer on the limestone.

However, with the proper chemical, I don’t think you’ll have any problem at all with a 40 degree tip, provided you keep the tip at least 12 inches away from the limestone.

On a side note, be extremely careful if you put 12% (or any concentration of sodium hypoclorite) in a pump up sprayer or any “closed” container! If any chemicals were used and even if the slightest amount is still in the container, a chemical reaction can cause the container to explode. It won’t be a little explosion either!

I should have been more specific,when i say 12% i mean at a 3 to1 or 4 to1 ratio. Of course that all depends on how severely stained the area is?

First pretreat the area with a mixture of bleach and a surfactant. I use Simple Cherry. It works synergistically with bleach, allowing me to to use weaker solutions with superior results. It also neutralizes the bleach odor.
2% bleach hitting the steps should do it, even if you just add some non-Ultra Dawn or other dish soap with no alcohol. Give it some dwell time and hit the trouble spots again if needed.
Be sure to kill the mold before you remove it. If you just blast it off and leave live roots in the limestone it will come right back. If you pretreat thoroughly you will be able to clean it with very light pressure. I use a 1540 or 1530 for stuff like that.

Thank you all for the info on this, it has been a big help .
A Clear View Window Cleaning

Maybe its just me, but I have used bleach, simple green, home depot house cleaner and I have even mixed a few together and I have never seen any thing works all that well. My PW all by its self removes mold, mildew, dirt and just about any thing else. My clients all say there house has never look so good. This doesn’t mean I will stop trying different things. I just haven’t found any thing that work for me or that saves my any time.

Bill bring a 5 gallon bucket with a lid when your down here in a couple of weeks. I will send you home with some 12% Bleach and some “breakthrough”. Its all about just letting the chem do the work. In the long run it will Definitely save you time.

I am all over it!!!

Get you some 12% and “simple cherry” you’ll be good to go!:wink:


I don’t know much in regards of power washing but why not use a rotary cleaner?

now you may tell me that this will cut into limestone, but i don’t see why it would.sure limestone is a soft rock but i have come across rotary cleaners which state that they work on limestone.

i suppose one could say a rotary could work on limestone in scarifying the limestone. but i don’t see why you couldn’t get one which polish.in fact i believe i have come across them before.

Rent one if you can.
i believe some people run business by use of these rotary cleaner alone
I could not believe the results when i first came across these…(see picture)

Plus it seems especially effective for dirt mold and mildew etc…

If you use bleach to kill the mildew or algae before you remove it the client’s property will stay clean longer (not always a good thing, I know :wink: ). Removing surface growth looks great but the roots are still alive in the substrate and come back more easily.

Also, is someone like me comes into your neighborhood and sells my Softwash against you blasting their property…

The rotary cleaner used with a power washer doesn’t use rotating brushes like a floor scrubber. It uses pressure washer tips on a rotating bar. The brush skirting is just to keep water from flying everywhere.
You can damage concrete with an improperly used surface cleaner and you can definitely tear up some limestone. You need to know what tips to use, monitor psi, and control other variables to do the job correctly without damage.
That being said, anyone who cleans concrete needs to call Bob and get a Classic. Whisper Wash Classic (DELUXE) - Pressure Tek

I do have an X-jet, I am going to try it with Chris’s mix and see how it works.