Cheap safe auto-topoff

[brad]

I read your ReefKeeping article about the dangers of autotop off. While my system isn't foolproof, it is immune to most of what you mention in the article, and it cheap and easy to set up.

I have a solenoid connecting to my RO. Power to the solenoid is on a $10 timer I have for lights. The RO runs into my sump through a float switch.

I do have to carefully adjust the timer so it replaces exactly what evaporates. But if I am close, it is the difference between adding 5 gallons a day and 5 gallons a year.

If the skimmer overflows (or anything else lets salt out of the tank), extra water will slowly get added but the water level will drop. Salinity will remain constant, even until my pump sucks air and dies.

The only way the system fails is if both the timer and the float switch fail at the same time in the on position. There are a lot more probable ways I could lose my reef.

Yes, if someone dumps loads of copper or pure ammonia into the water, I will lose the reef. But wouldn't I lose it if I added the water manually?

[melev]

So basically, you set the timer based upon the amount of water your RO/DI can produce for the exact amount of water your tank can evaporate daily, correct? If the tank evaporates 3g in the summer, you'll run the timer for 40minutes, and in the winter maybe 55 minutes?

I understand how the solenoid is normally closed, and is opened when the float switch drops in the sump. How does the timer come into play?

Both of those parts can fail at the same time, and while the chances are remote, it does and has happened. It sounds like you are being very observant, which is key to keeping a successful tank.

Yes, if you added water that was polluted with ammonia or copper manually, your reef would suffer. The point of the article is to limit as many risks as possible to avoid a catastrophe to the tank as well as to your home.

[melev]

Btw, here are a couple more posts on this topic, posted in my 280g thread:
http://archive.reefcentral.com/forum...43#post9906943