Low level water detection?

[dudemeister]

I have successfully moved my sump to my basement and expanded it. All is working well though I miss the slop sink but thats another project...

I have also installed the auto topoff/change using the Colley devised Tunze Osmolator on a relay switch. It works well and makes life a lot easier but I have one issue I would be interested in resolving.

The ATO changes about 2.5 gallons per cycle on the fly (twice a day which is enough for my system). The reason I only do 2.5 gallons is because I don't want to drain so much water to where the return pumps are in danger of running dry. What I would like to do is have some kind of switch in that part of the sump that can detect low level of water and cut off the drain pump to prevent the returns from going dry. Float switches aren't very practical because they obviously would need to be always under water and they will get gunked up with stuff and be prone to failing.

Does anyone have any suggestions or know of any products that would fit the bill? I looked on Aquatic Ecosystems but the one thing they have won't do it.

Thank you all in advance.

 

[scolley]

Mike - congrats on getting it working. I've got something that might work for you. It's a little unconventional, but it works like a charm. I had a similar problem years ago when I was working on a mechanism to do 95% auto water changes for discus tanks.

I got a fishing float (you know... think little red and white bobber, but without any metal parts) and suspended a small, powerful, plastic covered magnet attached to the bottom of it. The plastic is - obviously - so the metals in the magnet will not react with the water.

The float is on a string secured to the bottom. So it can only float as high as the string. The string length should be such that the float floats no higher than what you consider your low water condition. So when you have plenty of water, the float strains to go higher in the water column, but cannot - because it's tethered to the bottom.

Oh, and the float is tethered such that it's right up against the glass. And on the other side of the glass? A small reed switch, secured at the level of the magnet. So when the magnet is suspended by the reed switch, the switch is closed. And it remains closed as long as there is enough water. But as soon as low water happens, the float lowers with the water level, the magnet lowers too, and the reed switch opens. And your controller responds as needed to a low water condition.

It's a little unorthodox. But it's snail proof. The weakness is that the reed switch must remain in an exact spot on the glass. But if it get's knocked off somehow, you'll get a false low water reading. Which is not so bad. What will never happen is a high water reading when it's really low. That's bad, and that's not possible with this little contraption.

If interested gimme a yell. I've got all the parts. You're welcome to them.

 

[dudemeister]

Neat! I am not sure what a reed switch is but am looking forward to finding out. Thank you.

PS- ain't nuthin' wrong with unorthodox.

 

[scolley]

Mike - but before you try my little geegaw...

You said you checked Aquaticecosystems? Correct?

Because this thing is the NUMBER ONE thing I'd recommend. It does not provide feedback to your controller, but it will shut your drain pump down cold on a low water condition. Or a high water condition - FWIW. You have to get the correct model. But they are industrial strength. The seams on your tank will fail before these things fail.

I made my suggestion because it sounded like you had rules this out for some reason. So now I'm just making sure.

 

[scolley]

I am not sure what a reed switch is but am looking forward to finding out.

Just a cheap little switch that either opens - or closes - in the presence of a magnet. Dirt cheap. Massively reliable.

 

[dudemeister]

Mike - but before you try my little geegaw...

You said you checked Aquaticecosystems? Correct?

Because this thing is the NUMBER ONE thing I'd recommend. It does not provide feedback to your controller, but it will shut your drain pump down cold on a low water condition. Or a high water condition - FWIW. You have to get the correct model. But they are industrial strength. The seams on your tank will fail before these things fail.

I made my suggestion because it sounded like you had rules this out for some reason. So now I'm just making sure.

I did actually see those and I agree they would work well but they are designed for a tank that has room to operate- my sump has 3 pumps sitting in the bottom in a small area thus would probably not have enough room for that kind of float switch to operate correctly. The float would end up being physically held up by the pumps.

I like the idea of the reed switch solution also because (I assume) it can be worked into the Apex as well. It would work well on reservoirs (chems, RODI, salt water) as well. I look forward to checking it out with you.

 

[scolley]

Well you may be in luck. I was building prototypes when I needed this gadget, and as I recall I purchased several of each important part - with the possible exception of the floats. But that should be no big deal.

 

[dudemeister]

Another thread bump....

I did try Steve's reed switch but its a bit difficult having to keep the magnets aligned through the glass.

I was thinking of perhaps some kind of sensor that can detect through the glass like this

http://www.ebay.com/itm/12-24V-Non-...t-Sensor-Switch-Container-DC-5V-/311701843126

Anyone have experience with these? I was thinking if I floated ping pong balls on the water it might help the sensor detect better? (thinking out loud)

Thanks