Premiere H2O has a system that dumped the water into the hot water line, similar to a hot water loop, but in reverse. There’s a lot of caveats with that arrangement (doesn’t really work with a tankless water heater, for example).

When you say brine is that in seawater desalination RO or are you using that to include non-seawater RO reject water?

You could definitely use it as gray water but if you are filtering for contaminants, that water would have a higher concentration and if you were pushing it out as gray water, would those areas of the yard have higher levels potentially of contaminants?