Indian stone flags going green

[Stevemr]

Flags in our yard are going green.
Jet wash just isn’t shifting it.
When we had them laid last year the stone yard boss said don’t use chemicals on them just jet wash them.
But it isn’t shifting it!
Any suggestions?
General consensus on internet seems to be 50% bleach and water mixed and left on half an hour, then scrub and jet wash.

[OutInTheShed]

Not tried it on Indian Sandstone, but bio clothes washing detergent works very well on our paving slabs.

[Arrivalist]

Patio magic.

[Turn7]

Patio magic plus Nilfisk patio cleaner attachment works a treat on ours.

[Mont Blanc]

OutInTheShed said:

Not tried it on Indian Sandstone, but bio clothes washing detergent works very well on our paving slabs.

Yeah, this.

We've used biological washing powder on our Indian sandstone and it took the green right off in one treatment.

Buy a big box of cheap biological powder from somewhere like Aldi, get an old watering can, put 2 or 3 big cupfuls of powder into a watering can full of warm water, stir it up, then pour it all over the slabs. Brush it around a bit. Repeat with as much as you need to cover everything.

Leave it for a few days then hose it off or just leave it for the rain to wash off.

The biological enzymes kill the green algae.

[paulwirral]

Stevemr said:

Flags in our yard are going green.
Jet wash just isn’t shifting it.
When we had them laid last year the stone yard boss said don’t use chemicals on them just jet wash them.
But it isn’t shifting it!
Any suggestions?
General consensus on internet seems to be 50% bleach and water mixed and left on half an hour, then scrub and jet wash.

I’ve laid hundreds of metres in my own properties over the years and all I’ve ever done when they get a bit green is wait until it starts raining , squirt some bleach over the area and give it a scrubbing with a stiff brush and leave it up to itself to drain away , or jet wash as you’ve said .

[Purosangue]

hypochlorite put on neat get 20 litres from swimming pool firms then spray on leave for several hours then jest wash off


forget patio magic expensive at £20 for 5 litres sodium hypochlorite at £35 for 20 litres

Edited by Purosangue on Monday 4th November 01:21

[blueg33]

Purosangue said:

hypochlorite put on neat get 20 litres from swimming pool firms then spray on leave for several hours then jest wash off


forget patio magic expensive at £20 for 5 litres sodium hypochlorite at £35 for 20 litres

Edited by Purosangue on Monday 4th November 01:21

Its highly toxic to plants even when diluted, so you run a risk of killing anything growing nearby

[Rough101]

blueg33 said:

Its highly toxic to plants even when diluted, so you run a risk of killing anything growing nearby

Exactly, it’s a horrendous polluter best reserved for small areas where you can dilute it well and clean it up without washing it into the environment.

[JimM169]

BAC50 works great on our patio

https://www.amazon.co.uk/Benzalkonium-Concentrated...

[Sheepshanks]

Daughter’s house has a sort of semi-enclosed patio with a rockery feature that had gone horrendously green. I sprayed the whole lot with Wet & Forget using a garden sprayer and a couple of weeks later the green had gone completely. I suppose a downside is the results aren’t very instant.

We used to have some sort of softish stone patio and I was told not to jet wash it as it roughs up the surface and makes it increasingly susceptible to going green. It’s been replaced with porcelain now - that just needs mopping now and again.

[blueg33]

I have to say - on our patios - sandstone and limestone, a pressure washer with a patio attachment works perfectly well. No need for chemicals, just do it twice a year.

[TGCOTF-dewey]

You lot are rubbish...

Obviously the answer is a few thousand more PSI from a bigger jet-wash.

[Freakuk]

I use patio magic or something similar with a sprayer, spray on when dry and leave it, couple of days later it's all gone.

Timing is everything, you'll need at least a day of dry weather to let it do it's magic.

[Arrivalist]

Freakuk said:

I use patio magic or something similar with a sprayer, spray on when dry and leave it, couple of days later it's all gone.

Timing is everything, you'll need at least a day of dry weather to let it do it's magic.

Exactly.

[JimM169]

Pretty sure Patio Magic is just BAC50 but at a more diluted ratio and higher cost!

[ukwill]

I use Pro-Kleen Patio Cleaner.

It works very well. Spray it on and forget about it. You'll see a difference in days.

https://www.amazon.co.uk/Litres-Concentrate-Fencin...

[The Gauge]

OP, are you sure it's algae and not a Raj Green coloured sandstone patio

I had a sandstone patio installed last year, over winter it went a bit green and I gave it a soft clean with the jet washer making sure I didn't go too close to the stone, but as soon as summer arrived the green disappeared, maybe cus it's south facing?

[Somebody]

JimM169 said:

Pretty sure Patio Magic is just BAC50 but at a more diluted ratio and higher cost!

This. And Wet & Forget. Just buy BAC50 and dilute down. The only downside is that you don't see instant results as it takes a few weeks to clear.

Edited by Somebody on Monday 4th November 17:47

[Sheepshanks]

Somebody said:

JimM169 said:

Pretty sure Patio Magic is just BAC50 but at a more diluted ratio and higher cost!

This. And Wet & Forget. Just buy BAC50 and dilute down. The only downside is that you don't see instant results as it takes a few weeks to clear.

BAC50 seems to vary in price quite dramtically - does it vary in strength?

I get Wet & Forget from Costco when it's on offer for about £20.