What to do about water drainage stains on stucco?

I would start with renting a pressure washer for the day and see if that gets rid of the stains on the lower floor. If is doesn’t I’m not sure what to do. If it does get rid of them then you have a place to start. If a pressure washer works I would get a “cherry picker” and use that as long as your windows are accessible. I would never use a pressure washer while on a ladder. A cherry picker would be best for the third story.

Without seeing the property it is hard to estimate a price.

One thing is for sure. If you do the pressure washer thing, make certain you check carefully for any crack or weakness in the stucco. Your headache will be multiplied hundreds of times if you end up with water damage as a result of pressure washing if there’s a problem.

This link says to use bleach. http://www.ehow.com/how_5730775_remove-stains-stucco.html

Check with a large hardware store. They may carry a product you could put in the water to clean off the stains.

As a side note, mold and mildew can be removed with vinegar. I don’t know about stucco, but it is very effective at killing spores and is less damaging on the environment (plants) than bleach.

If it is orangy-red there is a chemical for that at Home Depot. We used to use it for the ground water that went through our irrigation system where the water would hit our house. We took care of it ourselves, but it was only the first floor. It works very well. I agree a professional pressure cleaner person would know how to take care of it.

Hydrochloric acid, sold as muriatic acid, will remove the stains, but it is very nasty stuff. Brush it on, hose it off, and make sure you wear gloves and protective eyewear. You can get it at Home Depot.

No no. Muriatic acid can’t be right, can it? That’s the stuff used for etching concrete.

What color are the stains? Color should indicate what is causing the problem.

faint black, I think resulting from poor drainage around the black window gaskets.

What removes the stains depends a great deal on their composition. The color could be from mold, organic matter (such as black walnut husks), or even leaching from the shingles on the roof. Likely it’s a combination of these.

I used to run a cleaning business, and I discovered that the chemical that removed hard water deposits at one house did not necessarily remove them at the next house. That was because the water came from different sources, and therefore had a different make up of dissolved deposits.

It just occured to me that the casement windows themselves may be responsible for the stain. If you are dealing with acid rain, that will dissolve the aluminum and may be the cause of the stains.

Faint black can be mold. Regular old pressure cleaning with a bleach like chemical would work for that. If it is paint running? You say the casing is black, that is a different problem, but that sounds unlikely to me.

Faint black, hmm. If the stains are at or under just the seals, you might be right about it being gasket runoff. I was also thinking along @snowberry‘s line, dissolving aluminum frames. Or like @JLeslie said, mold. If it’s mold, try a rag with a little clorox, in a not very visible area. If it might be fading paint runoff, rub the painted area of the frame with a finger,some of the faint black will come off on your finger.
A window cleaner service or a professional cleaner might have a solution.A pressure washing service might help also. I think the key is to have anyone who “experiments”, try it in a hidden area.
If you can find a manufacturers’ label or engraving on the glass or the frame, contact them.

Thank you all for all the help.

Take a peek at the outside of your aluminum windows. Are they showing signs of pitting, streaks, or otherwise indications of leaching?

@JLeslie , yeah, it’s nasty stuff, but it can be used for cleaning stubborn water stains from masonry. There is some more information here. Note that the article says this is a last resort, not a first resort. For that, you could try phosphoric acid, sold under various brand names such as Lime-Away and Coca-Cola. HCl can also be diluted to reduce the rate at which it works.