OK, so I am starting to design my new tank set up for when I move houses in a month or so. I will be posting pics as I actually build it and will keep this thread updated. I have been doing a lot of research on this subject and have seen a lot of issues with but I think I have managed to engineer a pretty sound solution that should work well. I am looking at a show tank approximately 5'x16"x18" with a sump made from an old tank I already have. Issues with auto water changer Fresh water conditioning
So the first issue is how to ensure that the water I am topping up my tank with is good for my fish. We all know that tap water has chlorine and other minerals that need removing. So I looked at using RO with a float valve as auto top off. The problem with RO water is that this pure water is not very stable and is prone to large Ph swings as it has no buffer. I then started looking at the inline chlorine filters that can be found in showers, but I am not convinced that they remove enough chlorine to make the water safe. So I have opted to go for an RO inlet but do small water changes more regularly (5% 3 times a week) Disposal of old water
The next issue is how I can remove a certain amount of old water. So im going to create two dry chambers in my sump. Chamber 1 will never have water in it but will have bulkhead drain that runs to chamber 2 with a solenoid valve that is attached to a timer. When I want to schedule the drain the timer will apply a voltage to the solenoid which opens the valve and drains the required amount of water into chamber 2.
Chamber 2 will normally be dry until the timer triggers the drain which will begin to fill chamber 2 with water from the sump. I will use a 12v/240v SPDT relay circuit (I will post a schematic once I have drawn it up) and float switch in Chamber 2 so that as soon as chamber 2 begins to fill with water the float switch flips the relay and turns off the return pump to the show tank and tuns on an inline pump that drains chamber 2 to my waste water pipe.
Once the required amount of water has been drained the from the main sump the solenoid valve switches off stopping the flow to chamber 2. Once chamber 2 is empty the float switch returns to its normal position the relay circuit flips back, turns off the waste outlet pump in chamber 2 and turns on the return pump to the show tank. Risk of flooding when parts fail
The waste water system above seems at first a little over complicated as you could just fit a pump on a timer to remove waste water. The reason for this solution is to prevent the risk of flooding.
The other comment I commonly found was people saying if your float valve fails on your float valve on your fill line the the tank will simply overflow all over the floor as it will continue to fill your sump even though it is full. My solution to this is an unimpeded overflow pipe from the main refugium in the sump to chamber 2. if the sump gets too full then the overflow will begin to fill chamber 2 which will trigger the drain action and start to pump water to the waste outlet.
If the disposal system fails then then Chamber 2 will fill to the top until it is at the same level as the refugium at this point when the solenoid value opens there will be no water flowing as both sides of the valve will be at the same level.
The only way I can have a flood scenario is if both the float on my RO inlet and the disposal system fail simultaneously. I may put a buzzer and/or LED on a float switch in chamber 2 that is triggered if chamber 2 gets full. The design
I have attached a 2d schematic diagram to illustrate the plan for the sump. I have also done a sketchup model of the sump linked below My Aquarium Sump design by Rich - 3D Warehouse
I plan to put multiple grade foam in the mechanical filter, then a carbon filter and bio filter in before the refugium.
More info to follow...
Im getting a little excited
Any thought or comments welcomed