We have this problem too and it is a natural phenomenon that affects some makes of shower more than others. In our experience Aqualisa showers are particularly prone to it.
When we have finished using the shower, we turn off the water at the thermostat. The water stops flowing but the showerhead does not drain completely is still half full of water.
This is due to natural physics, a combination of the angle of the shower head, the surface tension of water and the very small holes in the showerhead. This won't happen if the shower head is one of those large metal ones with large hole usually mounted horizontally.
And it can be lessened, when using an adjustable showerhead, by tilting it up or down after use but even then over time (and the effects of gravity or air pressure changes) the shower head may suddenly drain out but will sometimes retain water until its next use.
This may cause the following problems:
- If the shower is ensuite and decides to drain out in the middle of the night the droplets falling on the plastic floor of the shower cubicle make a lot of noise.
- As the shower head is half full of water it prone to develop mould in the holes and calcite collects more easily making it necessary to regularly clean the shower head.
This does not occur with shower units that are fitted with a spring activated drain valve in the shower head hose / pipe. When the water pressure is removed the spring opens and all the water in the showerhead and hose / pipe drains into the shower.
Some manufacturer's have this facility built in, others (including Aqualisa) have never considered it to be their problem. You pays your money and takes your choice!
It is certainly on my list of ‘Annoying things about showers that need to be fixed.
Strangely, most shower units in Cruise Line cabins have this facility fitted.