First time opening island house

[nhjenny]

We will be opening our house for the first time tomorrow. Just bought it last summer. When we closed it, we used non toxic anti freeze in the pipes, washer, drains, etc. This is maybe a stupid question, but one we forgot to ask the previous owners. When we turn the water on, what do we do with the antifreeze? I assume that putting it in a septic system is not a good idea. Help please