Weight of a water softener?

[mylifeisgood]

I expect they are heavy, but I have seen that smaller ones are housed on a shelf under the sink.
Is the shelf massively reinforced for these? Or is it just because they are petite?

I can't find any information about the weight of different water softeners, and as we are a family of six, I don't expect the under-the-sink ones will be big enough.
Can anyone help?

They should not be put on the shelf. It is usual to cut a hole in the bottom of the cabinet so they stand on the floor.

You have to tip sacks or blocks of salt in every few weeks, which is very awkward if they are under the sink.