A Near Perfect Auto TopOff System

I like my ATO so much, I wanted to give a brief overview of its benefits for any interested. This short article will describe my ATO, and perhaps enlighten you to DIY more aspects of your tank.

An automatic topoff system serves a few functions. First, it negates the need to carry buckets of water. It keeps our system's salinity constant by preventing evaporation, which will concentrate salinity. This provides our corals with a stable salinity, which might mean better growth and health of our livestock. It affords us peace of mind, and instills us with pride that we've sucessfully handed over another chore to automation.

With automation comes risk. What if our float valve fails? The fresh water delivered to the tank will not stop until we notice, and intervene. Go away for a weekend and you may just come home to your worst nightmare. Not only have you sustained personal financial loss, but if you rent; your neighboor's unit downstairs will be equally damaged, and that won't make you new friends. Combine this with the fact that you've just changed your marine tank to freshwater, and perhaps killed all your livestock.

I came across my system through trial and error, starting with a simple float valve, and later adding a solenoid switch. With these two components, fluctuation in salinity is a thing of the past, and chance of a flood is all but eliminated. I tell my wife that I think I have a better chance of winning the lottery twice in a row than flooding my house.

Let's take a look.

You need 4 things.

1. An RO/DI system with an autoshutoff valve (The ASOV prevents the RO/DI unit from producing waste water when it's not "running.")
2. A float valve for your sump.
3. You'll need a solenoid valve,
4. and lastly, a timer.

The RO/DI varies in price, but most come with an ASOV nowadays. The float valve is about $12. The solenoid valve is $39, and the timer is about $9. So far we've spent only $60 if we already had an RO/DI.

Here's how the components work together. The float valve in your sump calls for water when the level dips below your setpoint. The RO/DI starts to deliver water. When the water level is back up to mark, the RO/DI unit stops. This is fairly safe, but float valves can fail.

This is where the solenoid valve brings insurance to the party. A solenoid valve is a simple, electrically-actuated valve that only allows water to flow when it's energized. It is can be controlled in the same way we control our lights. Plug the solenoid into a timer, and it will only allow water to flow through it when it's "on." So with these two pieces, the RO/DI can only flow when both the float valve and solenoid valve allow. The beauty of this simple premise is a term we've all heard of: "fail safe." Fail safe means that "even when it fails, no harm is done."

In my system, the solenoid valve is on a timer set to come on for half an hour, twice a day, every 12 hours. So at 9 in the morning, the RO/DI is permitted to run for 30 minutes, and again at 9pm. This creates a happy coincidence where the RO/DI comes on only when the tank needs at least a gallon or so of water. Without a timer to limit fill intervals; the RO/DI would come on whenever the float valve dips (every 15 minutes or so), and deliver only a few ounces of water each interval. The problem here, is RO membranes are designed to get flushed clean every time they produce. But when an RO/DI comes on for only a few seconds at a time, no flushing takes place, and TDS creep begins. The result is less than pristine water.

So let's say I leave for work Friday morning at 6am. Because of the solenoid valve, the ATO won't deliver water to the tank until 9am anyway, and will only deliver what it can in 30 minutes before the solenoid switch turns it off. So even if my float valve becomes defective, the solenoid valve permits only 2 gallons of water to dispense at 9 am, and this won't happen again until 9 pm, at which time about a gallon of water has evaporated, and I'm home from work by then. Get the gist? What if instead of work, I leave for Vegas Friday morning. As my plane takes off, my float valve breaks. What's the end result when I get home? My tank evaporates almost 3 gallons a day, so at this rate in 3 days, my tank evaporates 9 gallons. Since my my RO/DI is limited to dispense only 12 gallons in this time frame, I might not experience a flood at all.

If the float valve dies, and there's no solenoid backup, my RO/DI could potentially dispense 75 gallons per day, for 3 days, and. . . well--you get the idea.

What if the solenoid valve becomes toast? If that happens, I come home 3 days later and my tank is low by about 9 gallons. Sure, my return pump might burn out; but I'd expect the GFCI would trip.

Could both the solenoid valve AND the float valve fail? Of course--but I have a better chance of being struck by lightning, I think.

To conclude, I've learned at work and in life experience that generally speaking--the simpler something is; the better. The beauty of an ATO system that is actuated by a float valve and governed by a solenoid valve, is its simplicity. There are not many parts to fail, and even if there is a single failure, disaster is averted. If the solenoid burns out, then I have no topoff at all, and no flood. If the float valve fails, the solenoid limits the damage to one gallon per day of potential flood water.

I feel this system is reliable, not prone to failure, and best of all, it's fail safe. In comparison, it costs pennies to build, compared to the more expensive "custom" ATO systems sold, that to me, don't provide the same peace of mind. For my dollar, this system is hard to beat. I'm a big fan of a good night's sleep--and any automation to that end, is worth its weight in gold.

I hope this short article has inspired you to explore the different options available for ATO for your reef aquarium. DIY is your friend; and a well-executed system will reward you with more than just financial gain and peace of mind. It will save you work, and you'll feel a sense of pride in knowing that you made it yourself!

 

Very detailed. Thanks. K+

 

Your word to picture ratio is in violation of everything I stand for! It is a really cool idea with the solenoids and timers, but when I left my RO/Di on all the time as my ATO I noticed significant TDS creep. I only had it hooked to a float valve in the sump and was living dangerously, but it was really nice to never have to worry about re-filling a reservoir.

~Will.

 

Nice idea. Have you considered the potential for the timer to fail? I had a timer fail "on" before.

 

Nice write up! And good timing because I was actually just researching ATO systems.

As far as temporary solutions go (weekend vacation), are float valves reliable solutions...or is it still risky? I'm basically looking for something else besides setting up a drip system...

 

IME, float valves like the type that go directly onto the ro line are an accident waiting to happen unless you have a failsafe "upper limit" switch to shut the flow off in the case of the lower switch's failure.

 

Thanks, TBELT.

Yes. I think you experienced the TDS creep for the reason I mentioned. Your RO/DI never got to run long enough for the membrane to flush. The solenoid prevents this.

Sure have. All components can fail. IME though, the timer is the least likely component to fail. I use the same timers on my lights, and in a couple of years, neither one has ever failed.

Being an electrician and working with process control in industrial applications; I've seen many different types of float valves. There are optical types that never get wet, there are magnetic types, and so on. I use this one:



I employ it such that the shaft is about 2" higher than the water line. The body of the float is on an almost 45 degree angle. This way, the metallic hinge and wingnut are never in salt water, and less prone to rusting. So far it's worked. There are more sophisitcated, streamlined types of float valves, but I like the simplicity of this one; and it hasn't failed me in nearly two years. I also periodically check the tightness of the wing nut that holds the angle of the float. No doubt, the optical, laser-actuated ones are probably the most sophisticated, but I've always been a fan of mechanical devices, and the simpler the better. With the one I use, it reall doesn't get simpler, so there are less potential points of failure. There are pro's and con's to all types, and good reasons to employ each one. For me though, so far, so good.

horkn, putting two of these floats in series is even more insurance. Some might say overkill, but I don't. The safer the better. With two floats instead of one, you always have another on standby. That's a fine idea! I've considered it, and someday might even put one into action, but as it stands, between the single float valve and the solenoid valve, I'm very comfortable at night.

Thanks for the input, all!

 

I couldnt have said it better myself. One pic for the bible that he wrote......unacceptable. He should know better than this, esp. that he's a Mod. I really hope that this is the first and last time this occurs.

BTW, great write-up, as always.

 

LUNA!! Good to see ya! I promise in short order to photo document the entire thread. I appreciate the written warning.

BTW, my offer still stands.

 

great write Sparky, i use the same float as well, they work great for 12 bux...