Well I violated garden automation rule 1. It almost bit me, but I managed to catch it in time.
What is the prime directive for garden automation?
Never add water to the system without you there.
If you are adding water to a system automatically, and without you being there to supervise it, there is always a possibility that it will fail. If it does fail, you must assume that you will have water flowing to the worst possible place, because as soon as it overflows, it will find a way to get there. And if you aren't there to stop it, within hours you could have a flood on your hands.
By not filling or topping off a system automatically, but doing it by hand, it means that under no failure will there be more water in the system than you expect. By having a certain amount of water in the system, you can at least plan for that type of capacity in terms of other failures (such as that pump running for too long). Use rubbermaid containers or drip pans to cover up to your capacity so there won't be any problems.
Avoiding carpet is of course key, but sometimes not possible. Put down a tarp and then some panda film on top if you are worried, and always plan for the worst, and all the water ending up in your drip pan.
And never add water automatically to the system. Never.