Stucco Help on house wash

Top pic is before bottom is after. I Did a house wash on stucco. It had black streaking. The front of the house wound up with more streaking after I was done. The other areas of the house cleaned up nicely just underneath the windows all had black streaks that wouldn’t come out. All the streaks looked the same afterwards except the front looked worse. I upped my downstream mix from 2.5 gal of sh and water with elemonator after a bit with another gallon and spritz of elemonator. Hit the shady side of the house 3 times let dwell longer each time for around ten mins last time. the owner said he treated the streaks previously with sulfuric acid. I’m not sure if it was just the front of the house treated with it. But the front came out looking worse than before I washed it. Help plz

This back part of the house cleaned up except just in the bottom corners of windows with black steaks

If you’re hellbent on down streaming stucco you could do it 10 times and still wouldn’t come clean. It looks like the streaks are darker because you pulled the top layer of funk off. Still got 67 layers to go if you’re downstreaming.

We x-jet all stucco and dryvit. It still use to take 3 or more passes until @Clean1 told us to pull the proportioner out of the x-jet. And it took 2 passes to get here what you see below. That’s almost a 50/50 or 60/40 mix. You’re probably getting 12:1 or 15:1 out of your injector. If you don’t have an x-jet buy one and tell them you’ll be back next week or fall in love with your pump sprayer.


This was 60/40 with a pump sprayer for a house we did last week. The only reason we pump sprayed this is to show him what could be done as a sample.

Damn man, maybe I need to try an xjet after all, lol. I just use a roof machine with a 40% or 50% mix and it works great. But if I can minimize the use of the roof machine, that would be awesome.

I’m shocked you got the results you did with downstreaming on that material. How long did that job take?

If I’m being honest, I hate the X-Jet because I hate carrying buckets around the building with it. Just seems like unnecessary work. I’ve got a roof system in a pile of boxes that I just haven’t had time to put together and I don’t really wanna run it out if the 55 gal barrel we got. Also, we’re upgrading to a bigger flatbed truck after the new year and I’d like everything to be completely self-contained on that truck. So I x-jet it is for now.

I tried f9 1:1 mix got these results with two applications. Any advice?

Yeah. You’re almost there. Now test a spot behind the AC unit or behind a bush at F9 2 to 1 and see if it does anything funky to the paint. Maybe like a 1 in square. If it does bring it back to 1.5 to 1. Or just make a couple more passes with what your working with.

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If the higher dilutions of F9 does funky stuff to the paint show your customer the test spots and tell them you’ll do one more pass at the lowest concentration you’re comfortable with and if it stops changing colors a stain is a stain.

The majority of all the streaks came out. Just that one section of windows has a light stain but customer was overall happy.

I had an email today for a house a little further away than usual. I was wondering from this pic if you could tell what kind of exterior this house has and if it’s washable? Could it be cedar?

What you mean take the proportioned out of the xjet ? And why is the xjet better then downstreaming?

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@Eco-Power The little plastic piece in the barb that proportions your mix.

You can get more chemical through an X jet than downstreaming.

You can get nearly 50/50 when you take the proportioner out. Our you could put in a 4:1 proportioner for a different application.

It’s not that it’s better. It’s just that it’s required for different ratios. I’d never x jet a vinyl house, but I down stream them all the time.

Sorry. Took a long weekend. I’m not complete sure what kind of siding that is. It looks like cedar, but then again it’s smoother and flatter than most cedar I’ve seen.

It looks lije the old painted asbestos shingles to me but it could be the large pressed cedar shingles. I really can’t tell because the photo is not that great.

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Has anyone tried changing the downstream injector to the one PressureTek sells. its a high draw chemical injector (part#6740) with a 20% draw rate at 9:1 ratio with my 3.5gpm Pressure washer. If im correct in a 5 gallon bucket using straight 12.5%SH with a 9:1 ratio downstream injector the final percent hitting the stucco would be 1.39%SH. Would 1.39%SH hitting home after down streaming be enough to clean stucco or is this strength still too weak?

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I’ve washed for 30 hours over 3 days and for some reason can’t sleep, but that doesn’t mean I’m clear headed so hopefully someone else will piggy back if this answer is loopy.

My personal opinion on high draw injectors is that they’re a tremendous waste of money. They just draw down your chem tank faster and you have to highly dilute your housewash mix. They still don’t give you the strength you can get from an x-jet even drawing straight.

AND they make proportioning injectors so you can leave straight 12.5% in the tank and use proportioners just like the x-jet to get your mix to 12:1 or 10:1 or 20:1 or whatever the project calls for.

On stucco with algae you need 3% SH minimum sometimes up to 5%. If it’s super light or annual washing you can down stream. I haven’t seen any less than 3% work with any effectiveness/efficiency and the only way to control that with any machine is mix it up and 12 volt it or x-jet it without a proportioner.