Mix not strong enough

Hey guys, so I was on a job today and was cleaning some brick bordering. I downstreamed 10% straight mix and let it dwell for about 15 mins before washing off. Barely anything came off though. I put the mix into a pump sprayer I had to apply directly and about 2 passes of straight 10% finally allowed me to wash it off. What options do I have without having to use a pump sprayer? Ill have to resize the pics before I can post them. Thanks for any feedback and advice.

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How old was the sh? I use 10% all the time from Walmart and it’s usually pretty hot!

Maybe 2 weeks old. If that.

For little stuff like those stones, I would stick with the pump sprayer, especially around vegetation because the stream is smaller and you can control where it goes much better. But if you needed to cover a much larger area with straight 10% I would say a 12v pump. You can build a small 12v setup for a few hundred bucks and have it in hand for those times when stronger mixes or things like acids are needed. Honestly, this is why I don’t downstream at all. I use a gas powered diaphragm pump. 10 gallons per minute and I have complete control of the mix I’m spraying. I’m not limited to whatever ratios I could get from downstreaming. I believe a dedicated chemical delivery system is the way to go overall.

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A tell tale sign of a sudden weak mix is an injector going bad.

Check it.

Sometimes they go bad after one wash.

Round up would have been easier


Thank you for the reply. Would you have any good links on how to build a good setup or where to buy the proper kit for a 12v or diaphragm pump?

I thought that may be problem too, but I figure I need something stronger anyway since almost all of the homes around me are stucco.

What do you mean? Or is that the classic fireman humor again??

The Bandit from pressuretek.com is great. If you have the funds and want to go 12v, buy one of those. But you can definitely build one for much less than its $1400 price tag. Get yourself a 5.5 gpm, 12v pump either from PressureTek, Northern Tool or Tractor Supply (I’ve used pumps from all three of these places and not seen any difference in performance). Then get a deep cycle marine battery from AutoZone for about $100, a 65 gallon mix tank, hose reel and 200’ of chemical line and your good to go. Obviously you can go bare bones and spend a very small amount of money or you can buy quality stuff that will last. I started my business poor as hell so I went cheap and just upgraded as I could. But everyone’s scenario is different.

Now I personally am I cheerleader for the diaphragm method, lol. Gas or air powered, both our AWESOME. With a 10 gpm flow rate and by far the most resistant to bleach and other corrosives, you can’t really go wrong with it. The downside is that these units, whether gas or air powered, will set you back $1500 to $2000 just for the unit. You still need your reel, hose and tank. Here’s a few links to check out for informational purposes. The first one is a local supplier for me here in Maryland where I got my gas powered diaphragm machine. The second one is run by a guy named Kevin. He’s in the business and builds these air powered systems that come with compressors, ready to go. Honestly, in hindsight, I should have gone air instead of gas because air allows you to “nozzle down” your flow rate. So you can be on a 10gpm air pump but only use 3 gpm of solution if you use the proper nozzle.



I’m sure there are others who know more than I do about these systems, but I did months of research before getting away from a 12v system. It’s awesome not having to charge batteries, lol. If you have any questions about these things just shoot me an email, bjwelch@knbgutters.com


I use a pump sprayer all the time for small stuff like that.


I just walk around the house with a pump sprayer with 50/50 pre treating tough areas like that, most of the time it’s real quick. Include that in your cobweb dusting and keyhole taping routine


Definitely. I keep 2 sprayers on hand just for stuff like this. But an entire house that’s stucco? I dedicated is my preference (after much trial and error, lol)

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This is a game changer lol. Thank you for all this great info! I have a lot of research to do.

You’re a brave man.

Upgrading is the name of the game in this business, right? Lol I just need to figure out which way is best!

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I just meant spraying straight SH around those plants.


Research is the key. This pro hear isn’t cheap and its wise to have the most info possible when making these larger purchases. Lots of people will say that having a separate chemical delivery system is a waste of money, another machine to maintain, etc. But just remember, if someone is downstreaming and the pressure washer experiences an issue that can’t be fixed on site, you still have the chemical machine and can do the rinsing with a garden hose. Hell, in the beginning, all I had was a 12v system to spray my mix and we rinsed with garden hoses.

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Eh, it was raining all day and I pressure, and rinsed after.