Over-designed salt water exchange system

[denzil]

If you're going to mix salt based on the salinity probe, how much would you trust it? My thought is to maybe have three salinity probes, measure their inputs, and average them out to decide whether salt should be added or not to the WC water before it goes into the DT.

 

[neuro]

Along with the same thought as @denzil, I've seen some DIY auto water changers using more than a few float switches as backup.

 

[rygh]

If you're going to mix salt based on the salinity probe, how much would you trust it? My thought is to maybe have three salinity probes, measure their inputs, and average them out to decide whether salt should be added or not to the WC water before it goes into the DT.

I am not really planning to auto-mix salt, at least in the first revision. Just fun to talk about.

Averaging would help in theory.
But you cannot run them at the same time, or you might get stray current from one to the other, which
would throw off the measurement.
They would need some sort of relay/isolation to run one at a time.

Note that these sensors are probably a lot more reliable and accurate in simple pure salt water,
with no critters and such like in a reef tank.

 

[Vincerama2]

Just be careful that your robo-water changer doesn't mess up and kill your tank with the wrong salinity if it malfunctions!

I'll stick to semi-auto....

Meaning I'll use a pump to transfer water back and forth between buckets, but I'll sit there and do it, I just won't be lifing buckets up.

V

 

[rygh]

Just be careful that your robo-water changer doesn't mess up and kill your tank with the wrong salinity if it malfunctions!

I'll stick to semi-auto....

Meaning I'll use a pump to transfer water back and forth between buckets, but I'll sit there and do it, I just won't be lifing buckets up.

V

Yes, definitely an issue.
I have two lists : Failure points, and things that kill the tank. See next two posts.

 

[rygh]

Possible Failure points

## Power outage.
The most common problem. Must handle it well, even if it is in the middle of a change cycle.

## Stuck relay.
It is not uncommon for relays to get stuck. Springs break, or they weld themselves on or off. Stuck off is not usually a big deal. Stuck on can be a huge issue.

## Stuck or dead sensor.
It is very common for crud to make float switches stick. It is also possible for any sensor to fail.

## Microcontroller failure.
The microcontroller can hang, crash, or short out at the worst possible time.

## Pump failure.
Very common for pumps to fail or stick. Note that on failure, siphon issues must be considered as well.

## Valve failure.
Very common for valves to fail. In particular, very common for float valves to leak. Note that on failure, siphon issues must be considered as well.

## User error, especially forgetting to mix enough salt water.
Sadly common. Needs to check that.

## Network connection down
The internet could go down, particularly after a power loss, so boot cannot rely on internet.

## Burst or leaky pipe
A burst is unlikely, but leaks are pretty common.

## Other aquarium event during change cycle
I could be working on something when a cycle occurs, confusing the program.

## Leak in main aquarium A leak in the main aquarium means the water level will drop. The automatic top-off could try to keep it full by endlessly filling with water.

 

[rygh]

Catastrophic events

## System pumps aquarium dry.
The system could get stuck pumping old salt water out of the aquarium.
Key fixes:
1) Make sure at least one inlet from sump to pump is fairly high, just below where it would normally stop pumping. That way, it simply starts pumping air.
2) Software will have a time limit on pumping, regardless of sensors.


## System endlessly overflow aquarium with fresh RODI water or new salt water.
The system could get stuck pumping fresh water back into the aquarium.
Key fixes:
1) Put an overflow float switch in the sump, as a “kill” for the pumps.
2) Software will have a time limit on pumping, regardless of sensors.

 

[tygunn]

So it sounds like you're going for a system to remove a large volume and then replace it?

Have you thought of using a double head dosing pump? Then you could pump water out and add it back in continually. In effect you'd be continually changing water.

Sent from my Nexus 5 using Tapatalk

 

[rygh]

So it sounds like you're going for a system to remove a large volume and then replace it?

Have you thought of using a double head dosing pump? Then you could pump water out and add it back in continually. In effect you'd be continually changing water.

Sent from my Nexus 5 using Tapatalk

Well, the plan is to change about 7.5 gallons at a time. Large is relative.

Continuous change is an interesting idea.
Two problems:
1) Matching in/out. A double head helps, but differences in tubing can cause
an offset. Over time, that will mess up salinity. And the drawback to double head is that you
cannot calibrate it, and run the different pumps for different times.
2) Running a peristaltic pump 24/7 means remembering to change tubes fairly often.

It would eliminate the need for the fancy water height check though.
And the previous posts in this thread about salinity monitors are getting me thinking.
Hmmmm....
Three pumps, all similar, and calibrated:
1) Pump old water out
2) Pump fresh water in.
3) Pump salt water in.
Combined with a salinity monitor.

You use calibration to try to match the in/out.
If salinity changes:
A) Pump timing can compensate a bit.
B) It can email me, and tell me to re-calibrate or change tubing.

 

[sfsuphysics]

Better hope your resolution and scan time is fast if you're thinking of integrating a salinity monitor to help with dosing, I know with my AC3 I only set it to record data every 5 minutes... 5 minutes is a life time if your pump is beefy enough.

One way I would do it, is before the thing starts make sure your ATO activity is done, that way the salinity should be the same. Then have a hose clamped to a certain height in the sump, it'll suck until it's dry and have a float switch for good measure to turn it off (the hose height is just the fail safe), then pump water back in and triggered off another float switch. Maybe have a couple salinity monitors one in your reservoir and one in the tank, just to alert you if something is drastically off or at the very least not do the water change.

Of course the devil is the details, and making sure your float switches don't fail... but that's all on you not me because no way in hell I'd try to automate a water change Seriously though I like to use the WC as a way to remove that detritus that always ends up in a dead spot or two in the tank.

 

[tygunn]

I have a Cole Palmer Masterflex dosing pump. You can actually get pump heads for it that have room for two hose sets. That means the same pump is dosing both lines at the same time. One for draining the tank, one for adding back. Of course there is bound to be some inaccuracy in this.

If you go for the dump and pump method, you can just use the same float switch you use to stop your ATO. So basically disable ATO, pump out until you reach some other float switch, and then pump back in until you hit the ATO float switch. Then you don't need to calibrate the pumps or anything.

 

[rygh]

Better hope your resolution and scan time is fast if you're thinking of integrating a salinity monitor to help with dosing, I know with my AC3 I only set it to record data every 5 minutes... 5 minutes is a life time if your pump is beefy enough.

One way I would do it, is before the thing starts make sure your ATO activity is done, that way the salinity should be the same. Then have a hose clamped to a certain height in the sump, it'll suck until it's dry and have a float switch for good measure to turn it off (the hose height is just the fail safe), then pump water back in and triggered off another float switch. Maybe have a couple salinity monitors one in your reservoir and one in the tank, just to alert you if something is drastically off or at the very least not do the water change.

Of course the devil is the details, and making sure your float switches don't fail... but that's all on you not me because no way in hell I'd try to automate a water change Seriously though I like to use the WC as a way to remove that detritus that always ends up in a dead spot or two in the tank.

Salinity monitor would definitely not be real time.
If nothing else, it takes a long to to distribute the new water through the tank and even out.
Not really in the current plan.

I am curious as to why you think this is so risky?
Some risk, sure.
But seems way less risky than connecting Kalk to your top-off, and many people do that.

 

[rygh]

I have a Cole Palmer Masterflex dosing pump. You can actually get pump heads for it that have room for two hose sets. That means the same pump is dosing both lines at the same time. One for draining the tank, one for adding back. Of course there is bound to be some inaccuracy in this.

If you go for the dump and pump method, you can just use the same float switch you use to stop your ATO. So basically disable ATO, pump out until you reach some other float switch, and then pump back in until you hit the ATO float switch. Then you don't need to calibrate the pumps or anything.

Yeah, still leaning toward the dump an pump.

 

[rygh]

PUMP THOUGHTS?

Assuming the original plan : pump out, pump in, about 7.5 gallons a cycle.
I need some pumps!

I want to pump it in/out in a few minutes.
Too fast, and sensors cannot react.
Slow is ok.
Way too slow, like hours, and evaporation will become an issue.

So ideal is 1-2 gallons per minute.

ALSO: My water shed is outside, and line needs to go up 8 feet, across garage ceiling,
and back down to sump. So 10+ feet of head pressure.

The little peristaltic dosing pumps are in ml/min, and just wont handle that.

A big Cole Parmer would work well of course.
But even used, seems WAY expensive. And hard to find the "Liters" per minute heads/tubing used.

I was thinking a diaphragm pump. Like this:
http://just12voltpumps.com/Delavan-2200301-PowerFlo-Diaphragm-Pump/M/B002NM3EOM.htm

Any opinions?

 

[tygunn]

What about a couple Panworld 30px pumps?
http://www.bulkreefsupply.com/pan-world-30px.html
256GPH and 10.1ft head (keep in mind the up and back down in the piping kinda negate each other except when the pump is starting up).
30w each.

 

[sfsuphysics]

I am curious as to why you think this is so risky?
Some risk, sure.
But seems way less risky than connecting Kalk to your top-off, and many people do that.

Never said it was risky, it's just that doing a water change for me historically has been a way to get a LOT of the detritus out of the tank (bare bottom systems). Yeah it often requires me to change my shirt after I do it because of all the wet, but it's manual removal of stuff. There is just no way an automated system would be beneficial for the my tank other than fighting my bout of laziness.

If anything you still need to keep on top of mixing your supply of water, if anything that would be your big danger point, if you filled up with fresh water and forgot to mix in your salt (as you said something for the lazy )

And I'm not sure I'd do a kalk w/ top off water either, I'd dose kalk based on a timer amount of water at most just because evaporation is not always predictable.

 

[rygh]

What about a couple Panworld 30px pumps?
http://www.bulkreefsupply.com/pan-world-30px.html
256GPH and 10.1ft head (keep in mind the up and back down in the piping kinda negate each other except when the pump is starting up).
30w each.

Hmmm.
Interesting looking at the flow curve.
At zero head, way too high of course.
But at 9 feet, nicely in the 1-2 gallons per minute.

That leads me to a new idea:
I have two Panworld 50PX-X pumps on my returns now.
I have been meaning to replace those with the new DC pumps to save power.
I could do that, and use the old pumps for the salt exchange.

 

[rygh]

Updated sump drawing.
1) Added a new float valve.
The analog water sensor will be for logging and backup/failsafe.
The cycle will simply go from one float sensor to another. Simpler.
** I may use one of those optical water sense switches instead of a float switch.

2) Pump is below water level.
So I can use a normal water pump.
Valves not shown in drawing, for maintenance, etc.

 

[rygh]

Here is a drawing of the fish water shed.

 

[Coral reefer]

I like this as an idea, and a thread for furthering our thing about it. But I wouldn't do it. I'd make it easy and quick to do the water changes without carrying water. One container for ro. A second for salt. One pump connected to both. You can fill salt from ro, recirculate/mix salt, or deliver either to your tank or top off reservoir with the flip of a few valves. That way you can do it in a matter of 15-20 min in a pinch. Way less chance for disaster. But hey, that's just how I do it, so of course I think that's the way to go.