On Fri, 17 Aug 2018 07:49:38 +0100, Handsome Jack wrote:

How do I make the outflow cleaner without replacing or modifying the
tank or drainage field?

The rules that have been in place since 2015 and have to be complied
with by 2020 are only applicable to systems that discharge into
surface water.

I doubt that there are many, if any, septic tank systems that
discharge into surface water. It's been standard practice for a very
long time for them to discharge underground into a drainage field or
soakaway.

--
Cheers
Dave.