Yes, I have been following his build. I think I will have to just give it a shot though and see how the herbie works on my tank. I have not glued anything yet because I want to have all the plumbing including the closed loop dry fitted first, so people can look at it and give me advice.

That's right. The primary drain (with the gate valve on it) is just a bulkhead on the bottom of the overflow. The emergency drain has a standpipe.

When you first turn it on, water should fall right to the bottom of the overflow box and go out the primary drain. As you close off the valve, you'll hit a point where the water level in the overflow box starts to rise. You want to dial up the water level as high as possible, short of the emergency drain.

My overflow boxes are only 12" deep. I found that I need to keep the water at least 6+" deep to prevent air bubbles being drawn down into the primary when the water falls into the overflow.

Ok that makes sense. So for water testing, I should start with the gate valve open completely and fire up the return pump and then start to close off the valve? Seems like a pretty good chance for a bit of an overflow until you get it dial in perfectly. How long did it take for you to set it? Would you also start by approximating how much flow you want to go to the refugium before you turn on the return pump? Does that make any sense? I guess I am trying to figure out how to get both herbies working together. Im guessing just a lot of adjusting until it works.

I have 4 separate Herbie overflows in my system and they are all inter-related. Any change to any of them affects the others.

Yes, start up with the gate valve wide open. It will be noisy and the water level in the overflow box will be right on the bottom. That will prove to you that you've designed with excess capacity.

Next test: Shut the gate valve 100% closed. This will test your emergency overflow. This is the test that will make you nervous as the overflow water level rises up to that emergency level. You need to know for sure that the emergency overflow can take ALL the volume. Be ready to stop the return pump, or open that gate valve fast....just in case. (and make sure that the emergency overflow actually has pipe connected to it!!!!)

When you go to fine tune things, you'll find that small changes to the gate valve make a difference. It also takes a while for the system to equalize after a change, so adjust slowly.

Ok that all makes sense but what about getting the refugium herbie and main drain herbie working together? It seems like it would be hard to work on fine tuning both at the same time, especially if you are starting with both wide open. I guess Im just a bit nervous. If it were just the overflow using a herbie, I would feel fine but the refugium one worries me.

While the two Herbies will inter-relate, it's no big deal. They will inter-relate because they can influence the water level in the sump. If the sump level stays constant, they will be very stable. Trust me, it isn't difficult to adjust multiple Herbies to achieve a steady state.

Remember, you should be able to flood anything, provided your emergency overflows are in place. If the Herbie valves get really mis-adjusted, then the water just flows down the emergency pipes and makes a lot of noise. You adjust them, and wait for the system to achieve a new steady state.

Here's some fun...I won't even attempt to explain this in detail...but I can manipulate the salinity of my system by adjusting the Herbie valve that runs between my small sump and the main sump. Hint: evap water is monitored by a float valve in the main sump. If you can get your head around that one, then you have achieve Herbie mastery!

Ooh, ohhh, I know! I know! .. By adjusting the Herbie valve, a robot comes online and goes and gets a cup of salt and then dumps the salt into the sump? Cool!!

I also guess a robot named Herbie!



Or maybe because you can let more flow from your smaller sump into the larger one and therefore not allow the auto top off to kick in even though evaporation is still the same.

But maybe both answers are wrong. Im not entirely sure how your sumps are set up!

Bingo! That valve controls the water level in both sumps, but evap replacement only happens based on the main sump water level. It was totally unplanned, but kind of neat when I figured it out.

You'll have exactly that same relationship between your fuge and the sump.

Yeah and if my fish do not behave I can threaten them with salinity changes! :twised: