If you connect your top up device to a large water reservoir and especially with a direct feed RO system and your float switch sticks on then you could completely flood your aquarium with fresh water which may wipe out your tank.
If your top up unit is connected to a kalkwasser stirrer then the results would definitely be terminal.
Use of some simple thought and a low cost timer could add a safety system which prevents all of this happening.
In normal operation your aquarium will evaporate a relatively standard amount of water each day. Your top up device will generally be controlled on a flow or drip rate to add a certain amount of water per period of time. Most top up systems will connect to a pump or a solenoid from the mains which controls when the water is swiched off and on and a simple timer added to this circuit can save a lot of heartache.
To determine the time that the water runs each day.
Set a normal top up rate into the aquarium from your pump or RO and start with the aquarium full.
Take a standard non digital plug timer and set it with all of the pins out to 12.00 and plug it between the controller socket and the pump or solenoid.
Every time the water level drops and the controller switches on it will also switch on the timer which will move round a little then stop when the water level is full again.
At the end of 24 hours you can read from the timer the total amount of time that the top up unit was demanding water�for that day.
Using This Information�
Now that you know that your top up unit runs for a period of say 3 hours per day you can use the timer as a safety system to restrict the amount of time that the top up device can operate. Set it to 3 hours plus 15 minutes extra and this is the longest that it can run even without a float device.
Instead of plugging the timer into the controller you can now plug the controller into the timer and it will only allow water to flow when the timer is on.
You can also control when the water is added by say dividing the�time�equally over the 24 hour period or setting all of the top up at night if you are using kalkwasser.