An answer to those who have had the problem that they can't turn the shower off.
I've had this problem with two Aquilisa power showers. The first one, installed approx 10 years ago, had the problem because moisture used to penetrate the housing and corrode contacts on a PCB fitted under the control knob. When this got bad enough it created a short circuit in the on/off part that had a mercury tilt switch. To solve the problem I had to regularly replace the PCB.
I replaced this shower 4 years ago with an Aquilisa Aquastream power shower that recently had the same problem, but this time it was being caused by a plastic arm that bears on two small leaf spring contacts that make the circuits for turning the shower on/off. One leaf contact is the initial speed, the second is the higher speed. The plastic arm slides forward in a recess (switch on) and returns back (switch off) when the rotary control knob is operated. My shower stopped switching off because this plastic arm was sticking in the recess it travels in. I believe this was because of a build-up of deposits due to moisture in the housing combining with other debris. (carbon powder from the motor brushes, perhaps). I eased out the arm and thouroughly cleaned and dried it and the recess it fits in, added a tiny coating of vaseline to the arm where it slides in the recess and replaced it. Result: shower turns off as it should do. A couple of comments. First, I used vaseline to lubricate the arm, this may not be a good idea as it may just attract a build up of deposits more quickly, so I'll keep an eye on that. Second, how do we stop moisture entering the housing, which I am sure is part of the problem. I was going to attach a photo of the plastic arm in position to this message, but I can't see a way of doing that in this forum. If anyone wants to see the photo reply to this message and I'll put it somewhere you can view it.
JW
September 2008