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Top-up System With Low Voltage Solenoid

Effective in Controlling Evaporative Loss.

In salt water systems the loss of water from a tank is by evaporation and this is of fresh water only, which will increase the salinity within the aquarium. This can be automatically replenished using a float switch and controller such as the D-D Multi Function Float Switch System. As the float switch rises and falls it switches the controller on and off, which in turn controls a pump or solenoid to top up the lost water.

This unit can be operated with any suitable 230V pump or solenoid valve in the same way as the low voltage units described in this document. It can also be used in conjunction with other equipment such as an audible alarm or similar.

For evaporative top up operation install the pump in a fresh water reservoir or similar container and connect the clear hose to the pump outlet. The other end of the hose should be inserted into the hole that has been provided on the mounting bracket. Ensure during normal operation that this end of the hose does not terminate beneath the water level, as this will cause water to back siphon once the pump is switched off.

Product Code RUW12LVS

Important Note:

It is possible for any solenoid valve to become blocked by a foreign body from the water supply so that it will not close fully and may still pass water. In order to prevent this occurring it is important that a number of safety systems are put in place as a back up should this occur.
We have shown two methods of operation for the low voltage solenoid valve and have described both systems.
The first method is to use the solenoid valve to control water flow from a reservoir, which is positioned above the tank or sump so that it will naturally siphon out and into the tank/sump. In the case of a solenoid valve or float switch blockage with this installation, the volume of fresh water entering the aquarium is limited by the reservoir volume. (See section on recommended timer backup if reservoir volume is large enough to cause a dangerous salinity drop).
The second method is to connect the solenoid and top up system directly to an R.O. unit to allow continuous replenishment. The volume of water that a mains supply R.O. unit can produce is infinite and therefore potentially disastrous to the aquarium. We would therefore always recommend that the there are at least three safety cut off devices operating on the system. These are:
  1. The float switch and controller itself.
  2. The solenoid valve, which should be always fitted between the filter pods and the RO membrane as shown on the diagram.
  3. Use of a socket timer prior to the float switch. This is described below and considered essential for mains water feed installations.

Use of a simple plug timer as a safety backup should the float switch or controller fail

To use the timer in this way it is necessary to first determine the duration that the RO unit takes to replenish the evaporative loss from one 24-hour period. Mark the position of the water level at its normal running depth in the sump or aquarium and then leave for a period of 24 hours without adding any more top-up water. Set the top up system running and measure the time taken to refill back to the mark.
With this information, the timer can now be set to just longer than the required time for full top up. If the float switch or level controller now fails, the timer will still switch off the fresh water supply and the aquarium will not become flooded. Be aware that his fill time may vary seasonally with evaporation rate.