Water hammer is a big lever that has a hammer on one side and a big bucket of water on the other side. Bucket gets filed by a water stream, gets heavier than the hammer and lifts it, and then at the lowest point (of the bucket) it is mounted in such way that the water spills and the hammer drops, resetting the machine. No precision technology needed, they could do it in stone age.
You can do the same thing with fireplace and water and it's certainly doable with ancient technology, but I'm not sure it's worth it when you have more running water than industry needs anyway.
Another thing they could do is Heron's steam turbine geared in such a way that it does useful work. Also not sure if it's worth it.
This trick (using low power to lift the hammer slowly and dropping it quickly) can be adapted to use any inefficient power source - hamster powered mills are possible ;)
You can do the same thing with fireplace and water and it's certainly doable with ancient technology, but I'm not sure it's worth it when you have more running water than industry needs anyway.
Another thing they could do is Heron's steam turbine geared in such a way that it does useful work. Also not sure if it's worth it.
This trick (using low power to lift the hammer slowly and dropping it quickly) can be adapted to use any inefficient power source - hamster powered mills are possible ;)