Herbie overflow and ATO placement

[Sstadler]

I have a 6’ RR tank that has a full siphon overflow on each side and one side has an emergency and the other the return. I am having trouble dialing in my Tunze ATO. I have the sensor placed in the return chamber of my sump. I have tried placing the ato line in the DT and in the return chamber. It seems that when I put it in the DT, it continues to fill the DT because of the fixed flow rate through the full siphons. When I put it in the sump, it seems that the ATO doesn’t fill because the level in the sump won’t drop until the DT gets seriously low. Except for evaporation in the sump.

I am at a loss here. Do I just continue to make minor adjustments until I get lucky? Looking for any and all suggestions. Thabj

 

[lapin]

The ATO goes in the return chamber. That level should remain constant. If you add or lose water anywhere in the system that level will change. The tank level is controlled by the overflow and return pump. If the overflow can not handle the volume then the tank will overflow so then pump will need to be turned down or a smaller pump used
Hope this helps

 

[Sstadler]

The ATO goes in the return chamber. That level should remain constant. If you add or lose water anywhere in the system that level will change. The tank level is controlled by the overflow and return pump. If the overflow can not handle the volume then the tank will overflow so then pump will need to be turned down or a smaller pump used
Hope this helps

Ive read this reply before but isn’t it wrong? If my water level stays at a full siphon because they overflows are dialed down with a gate valve, then my overflows will constantly stay at the same flow rate despite evaporation in the DT. My return chamber also stays at the same rate due to the return pump being set at a certain power level Also. So evaporation doesn’t flow rate between sump and DT?

 

[Joe31415]

Since water is passively falling out of the DT (via the overflow) the height of it will remain constant as long as other things are unchanged (pump is the same speed, drain is the same speed etc). Any increase or decrease in the amount of water in the system will be reflected in the sump, specifically the return chamber.
Look at it like this: Imagine the pump was turned on super slow and the overflow was wide open. The pump sends up one gallon/hour and as it gets pumped up, the DT dumps it into the overflow and it trickles back down. If you dump an extra gallon of water into the system, it's going to end up in the sump since the DT can't handle any more water as it'll just overflow. If you remove a gallon, again, the level in the sump will go down since the DT will simply stop draining until it starts overflowing again.

The level in your DT really shouldn't fluctuate by all that much and when it does it's going to have more to do with the speed of your return pump and how fast your overflow is running. The amount of water in the system doesn't play into it in the way you're thinking. Though a lower water level can reduce the flow of the pump, but that's minimal.

If you want to verify this, mark the current level of the DT and return section of the sump and check on it in 24 hours. If everything is set up properly, the sump will be down and the DT will be the same. You can then add water, anywhere in the system, and the return section of the sump will rise.

The short answer is that DT height is determined by your return pump and overflow setup and the height of the return section of the sump will fluctuate with the total volume of water in the entire system.

 

[ca1ore]

So evaporation doesn’t affect flow rate between sump and DT?

Not entirely sure what you were asking so I added a word LOL.

The answer is that evaporation will affect the flow rate of the return pump .... but this change will be so minor as to be practically negligible. The flow rate of any pump is affected by the head differential between the surface level of the two bodies of water. If your ATO triggers based on a 1" differential, then the head pressure will vary and return flow is slightly affected.

 

[Joe31415]

So evaporation doesn’t flow rate between sump and DT?

"So evaporation doesn’t affect flow rate between sump and DT? " Ah, that makes more sense. I wasn't sure what the question was.

Yes and no. The lower water level in the return portion of the sump means more head pressure so you'll get slightly less flow. A higher water level means less head pressure and the pump can move a bit more water. On my tank, the water in the overflow box is *just barely* at the top of the emergency overflow. If I top off the tank with enough extra water, the pump moves just enough extra water that I can hear it trickling through the emergency drain and splashing in the sump. Even when that happens, enough will evaporate for it to stop within a few hours.

So, yes, technically evaporation does affect the flow rate between the sump and DT, but (and least in my extremely limited experience) it's by such a small amount it's essentially negligible. I wouldn't go spending a half hour messing with the gate valve on the overflow in an attempt to correct for it.
In fact, once you get your ATO all set up, your water level will remain pretty stable. I went from seeing my sump down an inch and telling myself I could just top it off tomorrow to, after installing the ATO, never seeing it be more than an eighth of an inch or so above or below my line.
The other nice part about that is it allows me to keep the return section low enough to deal with the pump stopping and a gallon or two of water getting siphoned out. I have more than enough space for that to happen.

 

[Sstadler]

So still not really getting this. I’m gonna try to simplify what problem I’m having. So I have a full siphon on each side draining into my sump. Those are both dialed down with a gate valve so the rate is FIXED regardless of how much water is in the DT right? So my water level in my return chamber only lowers when water in the sump evaporates. Therefore, not sufficiently re-filling the DT when DT water evaporates. Does this make sense or am I crazy??

 

[Joe31415]

"Those are both dialed down with a gate valve so the rate is FIXED regardless of how much water is in the DT right?"
Kinda. While they should be tuned to drain out exactly as much water is the return pump is bringing into the tank. If the level in the tank does go up, there's going to be head pressure on them and more water will drain from them. There's not a whole lot of leeway here which is why you need an emergency, wide-open, stand pipe.
But what you said is basically what you need to know to get it up and running. The little intricacies you'll find out as you play with the valves and pump.

"So my water level in my return chamber only lowers when water in the sump evaporates"
It doesn't matter where it evaporates from. When the entire water volume lowers, it's reflected only (for the most part) in the sump. If your siphons are running at their max capacity and everything is balanced, when some water evaporates from the DT, the lower height will mean less water going down the overflow than is being pumped back up. The sump pump will correct the level and leave itself a bit lower.

You can prove this on your own by getting a pitcher and scooping out a bunch of water from the DT. The overflow will slow down until the pump fills the DT back up and everything will be back to normal other than the height of the water in the return section of the sump being lower.
In fact, you can remove water from any section of the DT or sump and the return section is where you'll notice.
It works the other way as well. Dump a pitcher of water in the DT (or anywhere in the system) and it's the return section of the sump that will show the increased volume.

"Therefore, not sufficiently re-filling the DT when DT water evaporates. Does this make sense or am I crazy??"
You're not crazy, it's just not a intuitive thing until you watch it happen with your own eyes. But just to clarify this, it makes no difference where the water evaporates from or where you add it. It's why auto top off systems can be in the sump even though the majority of the water is evaporating from the DT.

I still think the easiest way for you to see this happening is to mark the level on your return section of the sump and the DT with some tape and remove a bunch of water from the DT and see what happens after everything settles out. Then dump that water back into the sump and again watch what happens.

 

[Sstadler]

Update. It has been another week and have still been unable to dial in the ATO with the overflows. Continues to be the same problem. The ato runs until it is empty and the water overflows the DT. if I open up the valves on the overflow then the sump level gets too High. Getting discouraged on an impossible battle