Chemicals on driveway, pre-treat/post-treat?

jeffnc226

New member
I'm a small time pressure washer - only do it part time as part of my other home improvement business. I have a 4/4k machine. I use X-Jet when I need chemicals, rather than downstreaming. I also have a Blue Clean 383SS for smaller jobs/less pressure, that can spray chemicals (through the pump). My surface cleaner is a General Pump Hammerhead.

My question regards chemicals on residential concrete driveways, sidewalks, and brick porches/steps. I haven't seen any chemicals that do better than simple water pressure by itself. I used to do work for another guy when I started. He didn't know much about pressure washing, but he always had me prespray the surface with bleach (hand pump tank). At the time I was only doing small areas, with the wand only. The bleach made absolutely no difference as far as I could see in getting the surface clean. Black concrete turned light and clean in the exact same way with bare wand or pretreated.

I've since read in this forum that some people use oxalic acid to brighten concrete surfaces. One guy said he had good results by post-treating - applying the OA solution after cleaning, and then just leaving it. I have some I use for deck neutralizing, so I tried it. One section directly next to another section that only got pressure. Exactly the same, no difference.

So, what am I missing here?
 
I'm a small time pressure washer - only do it part time as part of my other home improvement business. I have a 4/4k machine. I use X-Jet when I need chemicals, rather than downstreaming. I also have a Blue Clean 383SS for smaller jobs/less pressure, that can spray chemicals (through the pump). My surface cleaner is a General Pump Hammerhead.

My question regards chemicals on residential concrete driveways, sidewalks, and brick porches/steps. I haven't seen any chemicals that do better than simple water pressure by itself. I used to do work for another guy when I started. He didn't know much about pressure washing, but he always had me prespray the surface with bleach (hand pump tank). At the time I was only doing small areas, with the wand only. The bleach made absolutely no difference as far as I could see in getting the surface clean. Black concrete turned light and clean in the exact same way with bare wand or pretreated.

I've since read in this forum that some people use oxalic acid to brighten concrete surfaces. One guy said he had good results by post-treating - applying the OA solution after cleaning, and then just leaving it. I have some I use for deck neutralizing, so I tried it. One section directly next to another section that only got pressure. Exactly the same, no difference.

So, what am I missing here?

I ask myself the same thing when I first joined on here. SH seemed to be the weapon of choice and it appears to be squirted on just about everything. Went through the same exercise as you obviously have looking for the magic that never came. I too use just water to surface clean but I will say I sometimes, with a pack sprayer, apply SH as an after wash treatment just to kill any remaining Algae that may be left behind in the final rinse. Even then I'm never sure that it is doing any good as I don't go back for 2 years or more to rewash. As for OA I only ever use it on rust as a PRE wash treatment. never used it as an after wash treatment (it's to expensive here in NZ) because I've never felt the need. As I tell my customers "What I use is a pressure washing wand not an magic wand, I can make it clean but I can't make it new." You can't undo years of neglect with a bottle of chemicals.
 
90% of the driveways we clean are very porous, exposed aggregate, and on real dirty driveways we will pretreat with a Bleach/Water/Soap mixture to help the cleaning go a little faster. Afterwards, we will then post treat, usually just downstream the same bleach/water/soap mix and let it dry, no rinsing. This really helps to brighten and whiten up the concrete. The problem with OX on a driveway is you have to be real careful and not let it dry, and also follow up with a soap water to neutralize it. If you don't then you can be left with a very splotchy inconsistent looking white haze. We never use OX for brightening a driveway. Bleach/water/soap only. IMO it is the easiest and best thing for it.
 
We roll the same way as Doug Rucker, but X-jet instead of doe streaming.


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Depends where you live... In the south, stuff gets moldy... I usually pre treat but it's not always necessary. Stay in the game long enough, and you'll learn when it's best to use it

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Like Doug,..we treat most of the time ,..especially if there is the round green algae/mold, running a surface cleaner over these alone will not remove them,..although the guys running hot water would have an advantage here I'm sure.
If I get into really bad stuff,..I'll use a mixture of Sodium Hypochlorite/Sodium Hydroxide along with some soap for dwell time. On large areas I'll just treat with my roof setup. Using SH as a treatment not only cleans better,..but it helps the concrete stay mold free for a longer time compared to just a water cleaning. Many times we will spray before we even start the main job,..let it sit there the whole time and it usually can be whisked away relatively easy at the end of the job. Once we do an initial cleaning,..future cleanings are much faster and easier,..but we still use SH to keep them easy to clean.

You guys using just water,..especially just cold water should try SH/Soap mix,..you will see that your work will be easier and look better when done. We use to do the same as you,..then we started treating,..and it made a HUGE difference in speed.

*What really sucks cleaning mold from is flagstone,..12.5% and lots of dwell time and multiple applications,..and when hit with any pressure,..it may come apart in layers. Not sure why,..but mold REALLY hangs onto flagstone,..especially the green kind I mentioned above.

Jeff
 
So I have a house solution with bleach and soap in it. You guys would suggest X-jetting this on the concrete, leaving it for a bit, pressure washing, then spraying more solution on when leaving and just leaving it?
 
So I have a house solution with bleach and soap in it. You guys would suggest X-jetting this on the concrete, leaving it for a bit, pressure washing, then spraying more solution on when leaving and just leaving it?
I pre and post treat on almost every driveway now. It makes a big difference. Once in a while a customer will ask me to rinse it off, but usually when I explain why I am doing it, they are fine with it.
 

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Nice work Ralph great before an afters dont really understand why anybody wouldnt pretreat really just makes for a faster cleaning job get rid of most of the dreaded striping problems that occur.
 
Well kiloman, the reason some people don't pretreat is because, as I said in my original post, that it doesn't seem to make any difference at all to us :)

But there are times I see some slight striping. It's pretty minor, I don't think a customer has noticed it after it dries. But I'm a perfectionist - if it really helps eliminate that, I'd try it.
 
Ok to each his on but if you say it doesnt make a difference you must not have washed alot of really dirty concrete just my two cents.
 
I believe I have cleaned some pretty black ones. It's just that the pressure alone looks the same next to the bleached area, and the same next to the oxalic acid area. I haven't tried pretreating with my actual house wash mixture, nor with leaving that on after. I'll try that. The problem is I'd have nothing to compare it to (the same driveway done without wash.) I'd like to try it on my own driveway first (half with, half without), but unfortunately mine is pretty clean right now.
 
Cleaned at least 200 driveways this year. Pre-treating saves time by making it a lot easier to clean, does a better job, works on stubborn stains. Post treating brightens and keeps cleaning, removes the stubborn stains and any lap or stripes remaining. I know for a fact that post treating cleans and brightens a few shades whiter. And all the driveways that I have post treated on are clean a lot longer. I use 1800 psi to clean concrete, and rarely have issues of stripping cream off of concrete. Not pre-treating means obviously using a lot more pressure to achieve the same result.
 
Well, I have a 4000 psi machine (as posted), so perhaps that's part of the issue. Of course if I could move faster with the cleaner on there, then that would be worth it too.
 
Well, I have a 4000 psi machine (as posted), so perhaps that's part of the issue. Of course if I could move faster with the cleaner on there, then that would be worth it too.

Be careful. At 4000 psi, you can do damage to some residential concrete. Not all concrete is created equal. If it's older concrete, highly porous, already damaged, or less than a year old, you run a high risk of damage. Pre/post treating allows you to clean at a lower pressure with the same or better results at much less risk.

I also have a 4000 psi unit, but only have 2500 psi tips on my surface cleaner.
 
Well kiloman, the reason some people don't pretreat is because, as I said in my original post, that it doesn't seem to make any difference at all to us :)

But there are times I see some slight striping. It's pretty minor, I don't think a customer has noticed it after it dries. But I'm a perfectionist - if it really helps eliminate that, I'd try it.
Watch this video from Craig. I have adopted his circle technique because I had problems with striping also. Using Craig's method this is no longer an issue. I also feel I make better time on a job and definitely do a better job because I don't end up going over the surface twice to get rid of stripes.
https://youtu.be/MFJZaP-2zxE
 
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