[suziequeue]

Out hydrometer reads the same whether it's in our cider, a bottle of shop bought cider or tap water.

Does that mean it's broken?

[lazybee]

I don't know if yours is broken, it sounds like you need a more accurate scale. In water it will read 1 (specific gravity), with water and sugar (un-fermented cider) it will read more than 1. water with alcohol (cider) it will read close to 1.

On a liquid gravitometer water is 1, so oil is about .6 to .8 (lighter than water)

On a gas gravitometer air is 1, so propane for example is about 1.5 (heavier than air)

Guess what I do for a living