When I built my sump, I also purchasesd a tank to store my RO water in, I have appromimately 65 Litres of RO water stored in it. This is all hooked up to my RO machine that fills it up . My automated topup system uses 5 solenoid valves, I know its quite a few but it does work really well! My RO header tank has a sealed lid on it to stop bits getting into it.

Some people ask, does the water you are storing go off at all? Well personally I doubt it very much, my tank evaporates about 10 Litres per day, andthe header tank only holds 65 litres, so its having a good continual change in my opinion. Its stored in a glass sterile tank etc, so should all be ok. Its so crystal clear when you look into it, you cannot even see the water.

Why Have An Automated Topup?
I have been criticised a few times, people saying whats the point, dont you think its a waste of money etc, ok so my auto topup has cost me about £150 in total but thats not much when you think of the hassle it saves you. I used to have to make RO water every day and watch the level until it was full, or I would have to pop to the shop and buy water etc, now I dont have to worry, I can go on holiday knowing my system will stay topped up, which I couldnt do before as I would have to rely on someone topping itup and not letting it run dry.

Purpose Of RO Water Tank
The Purpose of the RO water tank is to provide fresh sterile water for the automated topup system to use and also to provide me with 65 litres of fresh RO water for doing water changes as and when i need.

How The RO Header Tank Stays Full
My Ro water tank stays full because i have my IKS unit constantly monitoring the level. I built my own water level sensors so I have used one in the RO tank. Basically it opens solenoid valves "A" and "B" on the diagram below. It shutsoff when it senses water. As a fail safe to the digital method jamming open, as the water enters the RO tank, it passes through a manual float valve that when comes into contact with water it manually shuts the water supply off, this is located just above the digital one, so its a good fail safe. When the water level in the header tank reaches the cut off point it takes about 300ml drained off it to trigger the sensor again. It I drain the header tank it will refill upto the line in about 12 hours.

How I Maintain The Sump Level
To maintain a constant water level in the sump, I have used basically the same method as in the RO tank, a digital float valve and a manual one as a fail safe. The only difference is that when it needs topping up it opens solenoid valve "E" which just pulls fresh RO water from the top header tank on a gravity feed.

Automatic RO Machine Membrane Flush
On my RO-Man Ro machine I can obviously flush themembrane on it to help extend the life of the filters etc, in this sense my RO machine is no different to any other, but.... I have replaced my flush valve with a solenoid valve, valve "C" on the diagram below. But when this solenoid opens, I also open solenoid "D" as the other solenoid "B" might be shut as the main RO header tank might be full, this is why I split the inlet loop. The flush valve opens for 20 minutes every 2 hours every day, so my membranes are being flushed very regularly.

Water Change Facility
Part of my automated topup system has provided me with 65 litres of fresh RO water, I can only drain 65 litres off the tank every day in the event that I want to do a big water change as my RO unit cannot keep up otherwise. I can physically drain the whole header tank and it will fill backup to the line.

Water Outlets On The RO Header Tank
I have 5 water outlets in total on my header tank plus one for filling it up. I cut all the holes on the tank myself using a Dremel. I have 4 outlets that are a 1/4" fitting on push fit like on the RO machine, I use one of these for the sump feed and have three spare, maybe ill use one of for a Kalk Stirrer and one for a plankton reactor or something like that. The other main outlet is a 1" pipe, this is so that I can drain water off the header tank fast into a tub for doing water changes, this simply comes over the edge of the shelf with a tap on it. The other thing i did when i put the holes in the glass is smear silicon sealer round each one to prevent any leaks that might occur as when water is flowing out the leak it can be a bit difficult to seal it when wet. If you want to cut holes in your own tank, its straight forward enough but make sure you keep the glass really wet else you will break it.

Why So Many Solenoid Valves?
Some people might think I have gone over kill but you cant really do it safely without 5 of them in my opinion. Ok, I have one for the gravity fed feed to the sump from the header tank which it vital, must be there to open and close water. I have another one for the flush valve which is needed. Ok the other three, the main water feed into the RO machine is split two ways, and both feeds then both go back into one pipe, sounds crazy, but one valve is turned on at the same time the flush opens, and other is controlled by the water level of the header tank. So if the header tank is full that would be closed so the flush on its own wouldnt work, this is why I split the feed through another solenoid so it can open the flush as and when it needs it. The final valve is on the outlet from the RO machine, this is purely a fail safe for the Flush system if the flush valve fails and tops the header tank up, but then again thats also got a fail safe!

What Happens In A Power Failure?
In the event of mains power failure, my UPS system will kick in and hopefully keep everything in the sump room running, so thats the heating, return pump, skimmer, light etc, should keep it going for an hour or so. If the mains power is still not back bythe time the UPS runs out, then everything will fail in the off position and close so no water can get in or out, and the sump will fill up to about 1" from the top, obviously when thepower comes back it will start up and maintain the proper level. I have tested my system many times to ensure it does what it is mean to do. In the photo on the right, it shows the override valve, either incase of power failure or solenoid valve failure.

A Word Of Warning
On a personal note, I would not just rely on having digital water level sensors for a topup, such as that AquaMedic system and Peri Pump. If it jams on you will end up with a flood and you could be out at the time. In my opinion, you should always have it so that a manual float will stop the water flow if it gets too high. I personally think you are taking a big risk if you dont have manual intervention. I can go to sleep at night knowing my RO system cannot flood or worse still, flood my sump with RO water, I trust my fail safes. The only thing that will let me down if it does is the IKS unit as all of my Auto Topup system including five solenoid valves and two level sensors is controlled by the IKS unit.