If an Alarm goes off, do not do a runner but stay put, if you leave the property and your seen, what's to stop someone breaking in and blaming the w/c? or worst still the property has already been burgled?
If this is a problem you come across on a regular basis, then ask your custy for a contact number, if they don't give you the number get the number of the local police station, if the alarm goes off make contact with someone, don't panic and don't do a runner.
An alarm system by law can only sound for 20 minutes Max, then it resets, custy's system may be linked to a central monitoring station, they are never connected direct to a police station as some people may say.
If a property has an alarm fitted and the doors have door contacts fitted, if the door is an outward opening door, then stear clear of the top of the door, (this is more so on commercial properties) the contact is situated right at the top of the frame, if water hits the contact it causes a short circuit and off goes the alarm.
If they have window sensors on windows, then they may be one of 2 groups, 1. A very old system or 2. A Diy system, no matter which one it is, the chances are it will go off, if your custy has this type of protection ask them to get it serviced and the window sensors adjusted correctly, Modern alarm companies do not connect any sensors to windows now, they are now fitted to ceilings or walls opposite the glass and are called Break Glass Detectors (BGD) You will not set of an alarm system with this type of detector, only if you smash the glass will this happen.
If custy has left any windows open normally down stairs I.e.,Lounge, Dining room or hallway or even the landing window, these areas are often protected by infra red detectors (PIR's) and you shutting the window can cause the curtains to move, now if the ambient temperature is right, this to can activate the alarm system.
Just a couple of tips to avoid false alarms from sometimes poorly installed DIY or old alarm systems, as 95% of the call-outs I went out on, were down to end user error and not the fault of the system.