Do you even need chemicals?

I’ve been looking around and it seems that most people use pre and post SH solution, I understand this saves time but is that the only thing it does? If I don’t use any chemical but take more time will I still be able to get the same result? I am quite young so I have a good amount of time on my hands I would rather just do a few jobs super basic just using the wand to get my foot in the door, but not if that means doing a significantly worse job. This is for driveways btw.


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It’s the difference between a professional job and an amateur. You might be able to get the concrete looking good initially with just pressure but without SH post treat the algae will come right back and show off all your wand marks. I downstream straight 12.5% my pre and post treat its not hard to do

Some concrete I can’t get clean without pre-treating with SH. I have to go back with my wand and green tip and blast the heck out of it. SH is your friend.

So your telling me I can get a recurring customer every few weeks instead of months? :rofl: But 12.5%!! from what I heard like 2-3% is usually good how are you not killing the grass

This may not be the forum for you. It is for professorial washing contractors and some cats that add humor or food pics.


:man_facepalming:t3: Use a downstream injector and put your drop tube in straight 12.5. Depends on what machine gpm and injector you use what % draw you will get but it should be a bit stronger than your typical house wash mix and works well. If you’re applying it with a pump up sprayer or something it will take quite a bit longer but I’d mix it stronger like a 3-1 ratio water to 12.5% sh and spray away from plants

Oh ok that makes sense, thanks for explaining

Do you use surfactant with that or just straight sh? Also what does your injector pull, (i.e. 10:1 or 18:1?)

Is there a reason to both pre and post treat if the concrete only looks like this in the pic below? Or would you just post treat? Seems like pre-treating is only needed with thick moss or some other heavy build up. I generally just post treat when it’s like this…

Do you wash pots and pans with dried on food, or is it easier to clean if you soak them is soapy water for 10 minutes or so? I rarely post treat. I find a good 1-2% pretreat with surfactant and going at a nice slow steady pace, I don’t need to. IMO, leaving lines means you didn’t get it 100% clean and post treating is like a band-aid to hide it. I know many are going to hate me for saying that, but it’s true. If you have lines, those are left by cleaner areas that were overlapped and putting a strong SH mix will even out what you missed. For me, I don’t do a ton of concrete, so if a driveway job takes me an extra 10-15 minutes because I’m moving slow, that’s fine with me. I rather do that then put down a 3-4% mix and risk getting too much in the grass or someone walking on it before it dries and going into their house.

Again, I know this will get hit with criticism and most guys do post treat, but this is just me and my $0.02.

I never post treat. I never leave with lines or growth still on the concrete. The only post treat I may do it spot spray with a pump sprayer spots I missed after rinsing.

I almost always post treat with either HW mix or 3%, depending on the severity of the stripes.

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Seems like if you have to judge the severity of the stripes, you’re going too fast or need to try different nozzles.

It’s been diagnosed ad nauseam on here. I just get stripes no matter what, cured by 3%.


I think it could be said that it’s a matter of preference, and what works for each person. Post treating probably does get a deeper clean, being assumedly a 2nd application of SH, which will last longer before visible growth returns.

I also think it’s probably best left on a case-by-case basis, although we all tend to work with absolutes so we can have standard rules to make it simpler…

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Couldn’t agree more, that’s why I made a point to say in my opinion and just my $0.02. It’s a case by case basis, and for me personally, most cases it’s best to move slower and not bother post treating.

Either way, striping is due to the concrete not being fully cleaned, I think we can all agree on that. How you choose to get around it up to you.

Unless it’s due to damage…which is a whole other animal…lol

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I’ve watched other concrete cleaning videos (other than racer’s 16 hr video). I watch so many of them that do not rinse until they are done with the drive. You watch as they just keep on cleaning while the other section dries. THey never tilt the SC up to push water, they don’t go perpindicular, they run over everything. No wonder there are so many videos on repairing SC.

I don’t wash much concrete, as most people have asphalt drives and concrete sidewalks, or gravel or shale drives.

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What’s this? Push water where?