Well most folk should backwash into garden but I have a borehole so I dump into storm water drain 

Connected to garden irrigation system , so either way i have to water the garden so instead use pond water and fresh new water goes to the pond .

@adeelns That is interesting. Do you put into tanks first and then irrigate from the tanks?

@k-is-for-koi hi yes have a jojo tank and have it connected straight to my main garden line and veggie garden . So basically the jojoj water accumulates for watering potplants amd the watwrvhamge goes ditectly to garden

@adeelns brilliant idea. And if you are treating the pond, say for PP what do you do with that water when you do a water change.  Is that good for the garden.  I have alpacas grazing and I wonder if that would be good for them.  I have bought long sewerage pipes that I set up when I treat and then I empty that water into the road, which I'm not sure is a good idea either.

@k-is-for-koi once pp has turned brown it has no effect on plants or burning of plant roots . All goes to the garden . Never do salt so if i did then water would go to waste or get used to spray off the driveway .im almost certain that once pp has done its work that water is safe . And sterelized .

Adeel, you are correct, once PP water has turned brown it will have no effect on anything.

I am lucky enough to have a drum filter so my water losses are not high and I seldom do a "water change" as we know it. Lucky to also have a borehole to top up the pond. I actually like the slow water change that my pond gets, Around 75 Lt per day.