Top-Up Unit

As a top up controller with one or two float switches to control the replacement of evaporated water. One switch controls the pumping from a storage vessel (not supplied), the other, if opted for, provides protection to prevent the top up pump (not supplied) from running dry.

As maximum / minimum contact to control reverse osmosis units, in conjunction with a solenoid valve, or connecting to a reverse osmosis water reservoir.

When it comes to reefkeeping, there are numerous basic tasks we’d like to automate.

One of the most desired features is a way to top-off the tank automatically in order to reolace water that has evaporated from the system, and many beginning hobbyists may not consider how important this is.

As water evaporates, salinity rises in the display tank because salt does not evaporate.

The water simply becomes more and more saline the longer the hobbyist waits to add freshwater.
While some prefer to top-off their systems manually every day, it is easy to become lackadaisical and slack off on this important duty.

Others incorporate an automatic top-off system into their system, drawing RO/DI water from a nearby or remote reservoir.

Many reefkeepers, however, choose to run their RO/DI unit’s output directly into their sump, using a float valve to shut it off when the desired water level has been reached. This is something that has led to many heartbreaking disasters, and thus I’m strongly opposed to setting up a reef tank that is connected directly to an RO/DI unit. Things will go wrong! For example:

• If the float switch fails, even two switches used in succession for redundancy, water will be continuously added to the tank until its owner notices. This will drop the tank’s salinity and kill the livestock, plus flood the floor. This just happened to a friend of mine who travels a lot. Two switches failed, and he lost his livestock that he’d had for over four years
• If the protein skimmer overflows, especially if it is external (located outside the sump), RO water will be added non-stop until the owner notices, and this results in the same issues mentioned above.
• If the aquarist has the RO unit connected to a Kalkwasser reactor, and the float switch fails or the protein skimmer goes nuts, RO water will be added to the reactor non-stop, which mixes with Kalkwasser powder; thus the tank’s pH will spike and kill all the livestock. Kalkwasser has a pH of 12, and our livestock lives in a range from 7.9 to 8.3.

All of these things can and do happen - almost on a regular basis.

The reservoir should hold only enough water so that if all its contents were dumped into the sump, the sump would not overflow and the tank would be able to absorb that additional volume of freshwater without excessively dropping the tank’s salinity (RO/DI water) or raising its pH excessively (kalkwasser).

In a nutshell, I don’t recommend a fully automated system because something will go wrong if a hobbyist isn’t attentive.

We have the duty to inspect equipment to keep our livestock healthy and happy, and it takes only a minute or two each day to ensure that everything is operating correctly.
Our reef tank (a 1200 L tank, plus 500 L in the sump) has a 80 L top-off reservoir.

I use an Maxi jet pump to add more water to the sump when the float switch senses the water level has dropped, It can push only 20 L on a good day as it is on a timer.

If every drop of the reservoir was added at once, my tank would be unphased. The 80 L of top-off water it contains supplies enough water for four days.

So I just replenish the container manually every three or four days. It really isn’t a big hassle. If someone wanted to hook up his RO/DI unit directly to a reservoir like this, he could do so easily with a float valve. However, what I recommend is that once the reservoir is full, he should turn off the RO unit until it is time to refill the reservoir.

A few additional points:

• When going out of town or on business or holiday, turn off the water going to the RO/DI unit.
• If you are going on holiday and don’t use an auto top-off, determine how much water will evaporate from your tank for the number of days you’ll be away. If your sump has the space to hold that additional volume, add it slowly over a day’s time. Adding this much water may affect the tank’s salinity, as will all the evaporation during your absence, but this is undoubtedly preferable to returning home to a disaster.
• Using a dosing pump that matches the tank’s evaporation rate is another method. Dosing pumps can be regulated with a controller or an electrical timer which is the method I use. When purchasing a dosing pump, get one that closely matches your system’s needs. If the tank evaporates 5 L per day, the dosing pump should pump approximately 5 L per day, not 15 L per day. Oversizing the dosing pump is just another possible disaster that will strike when Murphy dictates.
• Using an electrical sensor float switch also works very well and are quite reliable, but needs to be cleaned regularly (especially when dosing kalkwasser)
• Using a controller to measure the tank’s pH allows for a degree of safety. If the pH rises too high due to excess kalkwasser being added, the controller can turn off the protein skimmer, causing that water to pour back into the sump, raising the water level and disabling any further top-off. The controller can be set up to close a solenoid valve to prevent any more water from being added to the system
• If possible, it is best to drip kalkwasser independently of the top-off (RO/DI water). The steady drip rate using the gravity method should be fairly safe in that it will never be able to overdose your tank.

Never believe that your system is immune to disaster. Even as you read this article, review your current setup and see if any changes are long overdue.