How to clean concrete?

[Saturn94]

Our concrete pool deck is in need of cleaning. Shaded areas in particular are really dark (mildew?).

Some years ago we cleaned it with a power washer, and while very effective, it left the concrete feeling rougher.

Any suggestions for how to clean it in a way that won’t damage the concrete and the surrounding vegetation?

Thanks.

 

[JoyfulNoise]

Bleach and trisodium phosphate (TSP) will get rid of mildew/mold/algae. You apply it using a bucket and scrub brush, let it sit and then rinse it. If the power washer left your concrete rough, then the pressure was way too high and/or the wrong fan tip was on the wand. They sell rotary spray heads that you can hook up to a power washer that are designed for hard surface cleaning. You may be able to rent one.

 

[Saturn94]

Thanks.

 

[Saturn94]

Bleach and trisodium phosphate (TSP) will get rid of mildew/mold/algae. You apply it using a bucket and scrub brush, let it sit and then rinse it. If the power washer left your concrete rough, then the pressure was way too high and/or the wrong fan tip was on the wand. They sell rotary spray heads that you can hook up to a power washer that are designed for hard surface cleaning. You may be able to rent one.

Any suggestion of how much TSP and bleach to use (say, in a 5 gal bucket)?

 

[JoyfulNoise]

Savogran brand TSP has always been in Lowe’s. Do not get any TSP that’s labeled as “Alternative” or “Green” or “Substitute” as it is not trisodium phosphate but sodium percarbonate (Oxiclean). You can also add borax to the TSP/bleach solution as boron is very good at eliminating mold. Borax/bleach is used on wood walls to remediate water mold damage.

 

[Saturn94]

Thank you.

 

[JoyfulNoise]

It’s also a good idea to use soft water if you have it available. Calcium will react with the TSP and form insoluble phosphates and carbonates which can leave behind a powdery residue. Using soft water would eliminate that. Rinse the area you treat really well. A hose with a good strong spray should be fine but if use a power washer then make sure you dial down the pressure and use the widest fan tip you have available.

 

[Saturn94]

It’s also a good idea to use soft water if you have it available. Calcium will react with the TSP and form insoluble phosphates and carbonates which can leave behind a powdery residue. Using soft water would eliminate that. Rinse the area you treat really well. A hose with a good strong spray should be fine but if use a power washer then make sure you dial down the pressure and use the widest fan tip you have available.

You read my mind...I was going to ask about any issues with calcium (ie using cal hypo if I can’t get bleach/chlorine). So avoid calcium; got it.

This is from our city water report. Is the calcium level low enough?

 

[JoyfulNoise]

Yep. That water report looks fine. Your water is considered “soft”.

 

[Saturn94]

Thanks.

 

[Saturn94]

@JoyfulNoise

So my spouse came home with this

Lundmark TSP No Scent Hard Surface Cleaner 1 lb Powder - Ace Hardware

Hot TSP solutions will darken aluminum may remove or degloss paints & enamels and may darken oak, mahogany and other wood surfaces.Find the HRD SURFACE CLNR TSP 1LB at Ace.

www.acehardware.com

The ingredients on the SDS sheet look different than TSP (trisodium phosphate). Is it the same thing? If not, can I safely use it to clean the pool deck without harming the surrounding vegetation?

 

[JoyfulNoise]

You can use it but it’s not TSP (trisodium phosphate). The stuff you gave there is sodium metasilicate. If you’re having mold issues, it will lift the mold away and get rid of it but it will not sanitize the surface and so the mold will come back. True TSP/bleach solutions not only lift away adhered substances but the bleach sanitizes the surface.

As I said, there are LOTS of products out there that call themselves “TSP” (because it’s not a trade name) and are not actually trisodium phosphate.

 

[Saturn94]

You can use it but it’s not TSP (trisodium phosphate). The stuff you gave there is sodium metasilicate. If you’re having mold issues, it will lift the mold away and get rid of it but it will not sanitize the surface and so the mold will come back. True TSP/bleach solutions not only lift away adhered substances but the bleach sanitizes the surface.

As I said, there are LOTS of products out there that call themselves “TSP” (because it’s not a trade name) and are not actually trisodium phosphate.

The instructions on the label for cleaning mildew say to add bleach, so I assume that would take care of sanitation?

I’m particularly concerned about whether or not this stuff will harm the plants around the pool. Would I be better off exchanging it for this?

Savogran TSP No Scent All Purpose Cleaner Powder 16 oz - Ace Hardware

A non-sudsing powdered Trisodium Phosphate compound that is formulated for heavy duty cleaning. Preferred by painting and cleaning professionals for removing heavy deposits of greasy grime, smoke, soot stains and chalked paint from walls, wood- work and floors. Removes mildew and mildew stains...

www.acehardware.com

(Should have gone myself or sent a picture ?)

 

[JoyfulNoise]

Does the area have good drainage? I’m not so worried about the silicate part but the excess sodium part. Good dilution and drainage is key to keeping soil sodicity down.

 

[JoyfulNoise]

You might consider tenting or covering any sensitive flowers while cleaning the deck to reduce the chances of overspray getting into leaf and flower surfaces.

 

[Saturn94]

Soil drainage is pretty good (never any standing water).

Thank you for the feedback and the tips. ?