Automating Water Changes

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So let's talk about automating water changes. I will discuss the automation of a single tank that is running on its own filter and then explain how the simple concepts can be expanded to multiple tanks. The idea is to have a holding tank for the water that you will use to do water changes. You connect a hose directly from your water supply to your holding tank. A water pump in the holding tank puts the water into the tank, which overflows into your house drain.

Step 1 is to get a holding tank that is of sufficient size to accommodate your water changes. You should account for the space left at the top and bottom when deciding on the size / dimensions of this tank. You will need heaters and a recycling pump in the tank so you cannot drain it completely when filling your tanks. I leave about 1.5 inches (4cm) of water in the tank. You also cannot fill it right to the top. There was no room in my fish room for a vertical tank, such as a large garbage can so I had an acrylic tank built. There is a spray bar made of PVC pipe attached to two small water pumps for circulation and two 200 watt heaters in the tank. You should have an overflow hole in your holding tank to ensure that you never overfill the tank. Since this system will be automated it is possible that despite your best efforts something goes wrong and too much water enters the tank. Place the hole at the top of the tank and put a good bulkhead fitting in the hole and run a hose from this fitting to your drain. I put a PVC elbow in the fitting with a small pipe on the elbow to allow me to determine / adjust the height at which the water will overflow.
The next step is to connect your water supply to your holding tank. I have poly hose for my water supply, you might have copper. What you do is insert a T-connector within the pipe in your water line. Make sure you turn off the water first and use Teflon tape for all threaded connections. I have two lines running to my water tank because I mix tap water and RO water in my holding tank. The water line must be controlled somehow so run it through a solenoid valve and then on to your tank. A solenoid valve is just an electronic valve that can be controlled with power. There are two types, normally closed and normally open valves. The name indicates the behavior of the valve when there is no power. You want the normally closed valves.
That means that if there is a power failure or when the time sequence for the valve to be open is done the valve will close. It is crucial that you use a normally closed valve. The hose from the water supply runs to this valve and then another hose runs from this valve to your holding tank. Since you have applied no power to the valve, no water enters the holding tank. The valve has two wires running from it. Using these wires you can control the valve. Just use an extension cord and cut off the end that you plug an appliance into. Strip the wires and attach the wires to the wires from the valve. Now if you plug it into the wall the valve will have power and the water will run. When you unplug the valve the water will stop. But we want this to be automatic, we don't want to plug it in and out. So we buy a timer from a home repair store and plug the valve into the timer and the timer into the wall. Now we can set the timer to turn the water on and off at a set time.
It's best to buy a digital timer rather than the cheap ones with the pegs that you insert to start and stop the timer. The digital ones allow you to set the time on and off within a minute of each other and are much more accurate. They also retain the current time during a power outage and therefore don't have to be reset afterwards. Obviously we won't know how long the water needs to go on and off before it will overflow the holding tank so we need a float switch to determine water level. The float switch that I bought has two wires running from it. You hook these wires to a single wire in the power cord going to an electrical device and the float switch then has the ability to turn on or off the device. There are two configurations for this type of float switch. Is the power on the device going to turn off when the water rises or drops? For our needs we need one that will turn off the valve when the water rises. The type that I bought is intended to be screwed to the side of the tank and then glued in place with silicon.
If your holding tank is glass this will not be feasible. In my case I didn't want to do this either since I wasn't sure about the height that I wanted the two floats in order to get the appropriate mix of tap and RO water. I also may change the mix in the future and would then have to drill more holes and close the previous ones. Instead I attached the float switch to a piece of acrylic, an inch larger than the switch on all sides. I drilled 4 holes in the acrylic and inserted suction cups in the holes. Now I can place the float switch wherever I want and move it at will. Take the extension cord that runs to the valve and cut one wire in the cord. Attach the two wires from the float switch to the two ends of the wire and tape the connection securely. The float switch now has the ability to turn off the power to the valve regardless of whether the timer has shut it off. In fact, you want to allow additional time on the timer so the float will always shut off the valve. I tested the time it takes to fill the tank halfway with tap water and doubled this time on the timer. That way the float switch will turn it off. If the float switch fails then the water will only run for enough time to fill the rest of the tank. If it overflows I have accounted for that by having an overflow hole and hose running to my drain. This will allow your holding tank to be filled on it's own. It is circulating by the water pumps and spray bar and will sit overnight so the chlorine should dissipate as well. You can add any additives that you want after the tank is full but before the next water change. The heaters will have sufficient time to get the temperature to the desired level.
Now that you have a way of filling your holding tank for use in a water change, you need to automate the emptying of the holding tank. This is easily done with most of the devices described above. Put a water pump in the holding tank that has sufficient power (gph) to push the water up the height that it must go to get to your tank. The length of time that it will take is not that important since it will happen with or without your supervision but it is best to get a reasonably strong water pump. Ideally the filling of the aquarium should take as little time as possible to allow as much time as necessary for the refilling of the holding tank. In my case I refill with RO water and that takes the most time of any process so I want to get to that step quickly. The water pump sits in the holding tank and a hose attaches to it and runs to a J-tube in your aquarium. Once you set the J-tube in the tank make a mark on it where the water level is and then drill a 5/32" hole on the inside of the tube on the aquarium side just at the water level. I drilled two holes here. This is to stop the siphon that will occur when you turn off the pump and prevent water from draining back into the holding tank. You can also get a check-valve for this line. If you drill the holes you must check them frequently to ensure that they are not getting plugged.
Put the water pump on a timer and set the timer for the time of day that you want to start the water change. Time how long it takes to empty the holding tank and set the timer off at about 5 or 10 minutes longer than that time. Cut one wire from the power cord for the water pump and attach the float switch wires to this wire and tape the wires well. This float switch should be one that turns off the power when the water level drops. Put this float switch in the holding tank at the bottom of the tank so that it will shut off the pump when the water level is about 1.5 inches (4cm) from the bottom. Now when you connect the water pump to the timer and to the plug outlet you can control the pump. It will go on at a set time and the float switch will turn it off when the water drops to the right level. If the float switch fails you will damage the water pump. There is no way to protect against this.
The question then becomes, what happens to the excess water pumped into my aquarium? Like the holding tank you need an overflow on your aquarium. For the amount of times that I have accidentally overfilled my tanks I need an overflow for them all regardless of whether I am automating anything. You can either drill the tank or buy an overflow box. The hose from either solution will just run to your drain. A well built overflow box will retain the siphon within it whether there is additional water pouring into your tank or not. The size of the J-tube in the box and the hose running from the box determines the amount of water flow that they can accommodate. Mine are 1.25 inches (3cm) and can handle about 600 gph. This is the final step in the automation. You would set your timers so the water pump starts first, let's say at 8:00am. Mine takes about 10 minutes to empty the holding tank. At 8:30 the tap water valve opens and the holding tank is refilled to about 50%. At 9:00 the RO valve opens and the holding tank is refilled to the top. This takes about 4 hours. The water pumps are circulating and the heaters are on the entire time. By the next morning the water is ready to go again. The digital timers have the added advantage of allowing you to set the on and off times by day as well as the time. This allows you to have your water changes done less often than daily.
If you have multiple tanks as I do this system will work by simply attaching all of the overflow boxes to a central trickle filter. The water will be continuously overflowing and being pumped back into the tanks as they are filtered. All you'll be doing is providing additional water during the water change. You should test this to ensure that the water pump is not so strong that the additional water overwhelms the overflow box and the aquarium overflows onto the floor. My water pump has its output diverted to two tanks to lessen the flow as well as providing new clean water to more than one tank. You must ensure that your central filter has an overflow hole in it that can drain to your house drain since you will be adding new water to the closed system.
I purchased the parts discussed here at:
Aquatic Ecosystems
� float switches and solenoid valves

Canadian Tire
� digital timers
Lifereef Filter Systems
� overflow pre-filter boxes
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