pitch wrote:
You should be able to just put a clean out fitting in their line before the tank. You need to check how their tank is sized to insure it can handle your dump. If they have a 4 bedroom home but there are only two of them you should be ok. If they have a smaller home and are already at their design limit there maybe a problem. 30 or 40 gallons in one shot maybe to much.
Can you get your rig close enough for a direct drain or will you use a macerator?
^ Pay close attention to this post ^
If you overwhelm the septic system, your problems could be huge and expensive. Ridex can be added after each tank dump, which will help it digest solids, but volume must be considered.