[Smurf]

Thanks...

How long did you let the hypo sit for before rinsing off?
Was it 14-15% Sodium Hypochlorite you bought before diluting it down?

[Aqua Power Solutions]

From experience I could use a pressure washer all day long but it still will not totally remove bad algae and black spot staining without causing damage to the substrate.

Depending on the surface your referring to cleaning Smurf, low pressure and heat will remove algae and lichen
J & S
2:1 mix of 15% hypo was too strong . Remember that hypo reacts a lot slower in the winter months due to the temperature so allow more dwell time. I would imagine that you have  saturated the surface with hypo rather than a light spray !
Ed

[Smurf]

Would you spray it on and jet wash off or jet it first to get rid of thick then lay it down. My front and back patio.

If you look at the before pic I can see quite clearly that the slabs are already looking worn (patchy) similar to the after pic so I don't think hypo had caused the problem in the first place myself. Just now it looks a whole lot cleaner it obviously stands out more.

[Smurf]

From experience I could use a pressure washer all day long but it still will not totally remove bad algae and black spot staining without causing damage to the substrate.

Depending on the surface your referring to cleaning Smurf, low pressure and heat will remove algae and lichen
J & S
2:1 mix of 15% hypo was too strong . Remember that hypo reacts a lot slower in the winter months due to the temperature so allow more dwell time. I would imagine that you have  saturated the surface with hypo rather than a light spray !
Ed

Sorry I should have said cold pressure washer not using something like a doff type system

[Smudger]

Well done for pasting the picture smurf, I couldn't be asked to look, but as I suspected there is clearly wear to the slabs, the hypo may at the very worst highlighted this, where the slabs originally had a lustre finish which over time has worn away, without being rude they look a cheap paver.

The best way would have been to have a pic of them cleaned and dry before the hypo.
Personally I have yet to see hypo do damage to any flag or paving slab, I've used it from 5:1 upto neat.
I have however seen pavers look like this, usually these textured types, smooth seem to age better, but can still show colour change on heavy trafficked areas.

Darran