Residual water (remaining water) can build up in the showerhead and then release after the shower has been turned off - this is called Drain Down.
This is more common in ERD showers, particularly in the overhead/ceiling/rain/deluge heads.
Deluge Head – Drain Down
The way that water is delivered by deluge heads means that they can, and do, release remaining water held in the showerhead over time. This is dependent on the unique setup and atmospheric conditions within the bathroom. This can happen minutes or hours after showering.
Drain down commonly occurs in two stages:
The first stage occurs directly after the water is turned off:
The pressure/weight of water held in the showerhead and pipework pushes past the showerhead nozzles, releasing most of the residual volume build-up.
The second stage of drain down, and release of the remaining water, is dependent on the atmospheric pressure in the room:
As the showering area cools after use, the pressure difference between the showerhead and the room is equalised, releasing any residual water in the showerhead. The speed of this second process is largely dependent on the weather and internal temperature.
Tilting the showerhead after showering can help drain the water away faster.
