Cleaning patio - Every spring my stones go green

[mandolin456]

I have a patio that I think must be at least 30 years old, yellowish natural stone, sandstone?

It is in a shaded area and gets a green slippery film every year.

I have jet washed most years but this year the machine has broken down.

Is there a non mechanical way of cleaning the patio and around 200-300 feets of paths made of the same material.

I attach some photos of the Patio. (Cant figure out how to attach)

Many thanks

[pepperday]

I know its not much help, but what about a yard brush?
At least its non mechanical.

[pepperday]

just had a look on this web site and there's a section dealing with stains.
And it answers your question. Sounds like you've got a continuous maintenance issue.

[Tony McC]

Bleach and a stiff brush.

Use the cheapest, thinnest, wateriest bleach on sale at Aldi, Lidl or Netto, the sort of stuff they sell for 14p a gallon, and dilute it 1:1 with clean water, then swill it over the paved area and scrub with a stiff brush before washing off with clean water. Don't use a thixotropic bleach, such as Domestos, or any other "clinging" type - the cheap stuff really is the best for this task.

Bleach doesn't damage the paving, whether it's concrete or the notoriously fickle Indian sandstone that turns bright orange as soon as an acid-based cleaner goes anywhere near it. It will kill off any algae, which is the biggest problem for the imported stones, and it will also kill off Yorkshire Fog (that bloody annoying grass that will grow anywhere except on a lawn), as well as lichens and mosses.

Treatment needs to be repeated 3-4 times a year, and care is needed if the paving abuts a lawn or a planted area, but because a weak, diluted bleach is used, it should be neutralised within seconds of hitting the soil.