Rainwater Harvesting vs cleaning your patio properly :)

[puntloos]

So - I have a rainwater harvesting tank, and to my knowledge all my rainwater drain pipes, both roof and french drain, are led into this storage tank. 

Great in theory, but one crucial problem is that any chemicals I might use to clean my patio will end up sprayed onto my plants

 

Not ideal.

 

How are you all solving this, and/or theoretical solutions welcome:
 

- Are there cleaning products that don't harm plants?

- Are there ways to shut off, or bypass the rainwater tank (into soakaway direct?) until we're done cleaning?

- Should I just empty my rainwater tank into the sewer after my bi-yearly patio clean?

- Can I somehow pump my 'chemical contaminated' tank contents into my soakaway?

 

What would you do?

 

Edited November 1 by puntloos

[Mike]

Don't use chemicals. I use a pressure washer with water only and it works no problem.

[Conor]

Mild soap, plenty of scrubbing, and water is all you need to clean a patio. Soap will breakdown well before it gets near your plants. 

 

Acid based cleaners should be avoided, but these will breakdown quickly as well.

 

Bleach and commercial cleaning solutions are your worst enemy here. 

Edited November 1 by Conor

[marshian]

4 hours ago, Mike said:

Don't use chemicals. I use a pressure washer with water only and it works no problem.

 

^ what @Mike said - get a turbo nozzle for the jet wash lance  - that makes short work of even the toughest lichen/moss/green