Ever notice that these cistern blocks claim they last up to 4 weeks, but you are lucky for them to last even a single week, if that!

I found the reason for this is when the cistern refills, the force of the water shreds the blocks apart.
So you need to get them out of the way.

I tried making a basket out of a rimblock by adding some extra holes at the bottom.
This works, but the rimblock isnt always stable, or the holes are either too big or too small and get blocked.

Found this pool float and adjusted the size to fit a cistern block.
Cistern block size is 45mm diameter, 20mm height

Only on my first test run, but again found the pressure of the water would affect the block.
So either place this in a corner where the refill pressure is low, or adjust the position of the refill pipe so the water is released away from the float

Note: I have tried to make it even smaller, and shorter to help reduce print times and fit very small cisterns.
However the smaller version did not float one a cistern block is put in.

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Just noticed another pool float file.
Even though Feher_Tamas' design looks better I think tom_wentworth's may be better, as well as better to print.
So I'll upload a remix of his as well soon