Automatic waterchange with top off design - please gimme some feedback
 

So i woke up in the middle of the night (4:37am) with this brilliant design for a automatic water change system

Here is the model of it:
http://dl.dropbox.com/u/2361330/Aqua...0build/AQ5.png

So here is basically what happens
All this is wired into the Apex controller and break out box
A pump sits in the left side of the sump by the skimmer and just waits for XXX time. When the time comes (lets say Sunday 4pm) Apex controller turns off the skimmer and return pump and solenoids. This levels the water out in the sump. The pump on the far right of the sump starts pumping out water from the skimmer area down a drain. Once it hits the lower float valve it stops the pump. Next the pump in the SW mix container turns on and starts pumping water into where the drain pump was pumping out of until it hits the upper float valve. BOOM, water change

After this is done, return pump is on, skimmer is on
solenoids turn back on and the sw mix solenoid starts pumping water into the sw mix container until it hits the float switch. i come home from drinking around 8pm, pour in XXX amount of salt into the sw mix container and wait until the next water change.

thoughts?

The water changes will only be as big as whatever my skimmer area can hold.

The only thing that I would throw into the mix is that when you turn off the return pump, your sump will fill with some additional water from the display until the back siphon stops. At that time, the water level will most likely be over your walled off skimmer area and you will be doing a much larger water change that you originally planned. As such, you just have to make sure you have enough fresh SW available to handle this amount.

That would be a lot of automation but it seems doable.

wouldnt it only be the amount of water thats in the pipe that is draining from the main display?

my SW mix should be big enough but if its going way over the wall i dont want the pump pulling in any refgium stuff.

It depends. If you nozzles for your return are below water surface they will drain until air is let into the pipe to break the siphon. Unplug your return and see how much of your display drains to give yourself an idea.

This is a similar design that I have in mind for my setup. I also have a similar controller (RKE) which can be programmed like the Apex. What I would do is time how long it takes for all of your syphon to break. Program that time, plus about 1 to 2 minutes into the Apex just before the it starts your pump in the sump. This would prevent you from dumping out too much water from the sump.

Seen a really simple automatic water change system (believe was on RC) that was just dual matched dosing pumps running at the same time, one to pull from a reservior, other from the sump. Pumps were on a timer with on times throughout the day to change about 15 litres.

No high flow pumps, no float switches or water level sensors to mess up. Being matched wouldn't confuse a ATO.

Good idea. Only hassle I think you will face until you get it totally figured out is salinity.

I don't see anything inherently wrong with the design but (and I don't know if the apex can accomodate this) I'd suggest that you have to push a button or something when you add the salt to your mix tank. That would preclude you forgetting to add salt and having a bunch of fresh water added to your tank by mistake.

The ATO wouldn't cycle again until the button had been pressed, confirming the water for the cahnge was in fact, salt water.

auto change
 

the only problem that i really see is the build up of deteris in your display tank-i do a 30-35 gallon change every week in my 220,and i have to do it manually just to get rid of the excess deterus