I attach a diagram of the LG Therma V base pan showing five drain connection options. they usually come with drain plugs installed to be removed as required.

The best solution, of course, is not to have a leak in the first place!

This is why we insist on FGas registration to ensure that proper procedures are followed.

No gas should enter the system unless you are sure that the system holds a vacuum and passes pressure tests.

Never been asked for a soakaway across a wide range of manufacturers over decades.

I have just checked the LG manuals for the Therma V and they are more concerned with fixing the unit to a secure base.

Most manufacturers require a concrete base with the unit mounted on anti vibe mounts with adequate drainage, given the small amount of moisture produced during defrost.

If in doubt, pipe it away.

4.2 Safer design of the condensate discharge

The product contains R290 refrigerant. In the event of a leak, escaping refrigerant may get into the ground via the condensate discharge. The refrigerant must not get into the waste­water system. For the ground installation, the condensate must be discharged via a downpipe into a gravel bed which is located in the frost­free area.

4.3 Safe execution of the condensate discharge,

The downpipe must flow into a sufficiently large gravel bed so that the condensate can trickle away freely. To prevent the condensate from freezing, the heating wire must be threaded into the downpipe via the condensate discharge tundish.
The downpipe must not be connected to an existing underground drain pipe that is connected to the waste­water system.

I assume it's because of the R290 refrigerant, which (courtesy of google) is propane.  But this is only in the event of a leak, it would normally be just be water that is discharged? 

But don't forget I'm just looking stuff up and don't have any experience of these matters!!