Brick patio has whitetried to power wash. Just lines all over
Looks like you scored the brick, use the fan setting and lower pressure. The white is probably efflorescence that is minerals from the concrete that forms with water exposure. You can try just using a stiff garden broom, or a a solution of muriatic acid.
https://www.youtube.com/watch?v=lAaO7yqBgHo be sure to wear protective glasses, rubber gloves, and I would suggest rubber boots. Personally, I would seal it after the treatment.
Dilute vinegar at a ratio of 1 part vinegar to 3 parts water. Alternatively, use 1 pound of trisodium phosphate combined with 2 or 3 gallons of water. Vinegar is the better choice environmentally. The acid content neutralizes the alkaline salt in efflorescence, aiding removal. TSP is stronger, however. Dip a brush into the solution and apply as before or spray onto the wall and scrub. Rinse the brush frequently, using a small bucket with the sprayer. Wait 10 to 20 minutes to allow the solution to work.
Rinse the equipment and the wall with fresh water. Use a clean sponge, cloth or sprayer. Cover the entire wall, change the water if using a bucket, and rinse the wall again. A third rinse is a good idea. Chemical residue from either TSP or vinegar will degrade the brick.
If that doesn't work try the method below. It is a lot stronger and less friendly to the environment.
Mix a solution of 1 part muriatic acid to 12 parts water if previous methods fail to remove the efflorescence. Put on gloves and a respirator if working indoors and wear long, protective clothing. Measure the acid into a plastic or glass container -- any other material is dangerous -- and pour the water into the acid to avoid backsplash. Use a broom or long-handled plastic brush to apply the acid; metal reacts chemically to muriatic acid. Keep the windows open to ensure adequate ventilation. Start with a wet wall to limit absorption and rinse at least three times. Outside, the preferred location to use muriatic acid, cover plants and grass with plastic or saturate with water to prevent damage.
The last 3 sentences are important to keep this from happening again.
Seal the brick with a saturating masonry sealer to protect from future efflorescence. This is because brick is very porous and water might seem harmless but it has salts in it which will cause this to happen again. Wait until the brick is completely dry. Follow the manufacturer's application instructions.
I would use a stiff brush and vinegar. Once efflorescence is removed, rinse, dry and use sealer.
Wet the bricks with take a garden sprayer and spray with Clorox leave it set and the efflorescence and green alge should disappear. I use my power washer on our brick walk and brick patio after I do the aforementioned.
I used to power wash my patio until a found a new product this summer! It’s called “Wet it and Forget It”. I found it at Lowe’s. You spray it on and over time the area looks cleaner and cleaner. You will see some results immediately, but it will continue to improve over the next few weeks. Just spray, no scrubbing! I sprayed it on my patio, shed, sidewalks, brick wall, and garden statue. If the area is very dirty, you may need to do it twice. Be sure to really saturate the area.
You're right, Jean! Wet n' Forget is amazing. It saves hours of scrubbing vinyl siding, repeatedly sweeping patios and walkways of algae ( or worse, removing it by hand).
I hope sean tries this. Although you may not see instant results, it's so worth using this product, which can be purchased at a discount from Costco.
Based on my past experience let my emphasize two of the above answers:
Sharon is right about the spray pattern. It needs to be wider. Sometimes there is a adjustment on the nozzle or you might need another nozzle which will create a fan about 2 inches wide. You can clean this area with overlapping strokes in about 15 minutes
I have used wet and Forget
Jean Wright is correct
I have used Wet and Forget and can recommend it. It saves a lot of work.