Can water siphon thru Maxi-Doser tubing?

[Dr. Jim]

I've had my sump fill with water a couple of times and have had a difficult time figuring out where the water is coming from and why. I have a somewhat elaborate ATO system with 3 pumps, an Optical Sensor with back-up Float Sensors (one above and one below the optical sensor) and a complicated Programmable Logic scheme, any of which could be at fault.
My sump filled again during the night and I now have suspicion that water is siphoning thru the Maxi-Doser tubing. I was initially concerned about this possibility when I set it up but watched closely for siphoning previously and never saw it occur. But I'm wondering if there may positions of the dosing wheel where water is allowed to seep.

Has anyone witnessed siphoning, or would you say that my suspicion is plausible?

My other 2 ATO pumps are Sicce pumps which I know will siphon so I have the outlet tubes empty into a PVC pipe that is higher than the RO/DI reservoir level. (See photo). For now I've re-routed the Maxi tubing so it is also entering this pipe which will eliminate the siphoning possibility (but I would like to know for sure if this was the culprit). The photo shows the pipe coming up the back of the tank. The (lower) red and the blue tubes come from RO/DI reservoir (one for "KALK Pump" and one for "Backup Pump.") I now placed the Maxi (upper) red tube in the top of the pipe, temporarily, at least, until I figure out the problem. (The Maxi is used for RO/DI "Non-KALK" water). Previously this tube was in the sump (below the reservoir water level).

On a related subject: I have had occasions to believe that my Optical Sensor has not turned on, and has not turned off, when it should have. Has anyone had problems with the Optical Sensor not functioning as it should? Luckily, my backup LOWER and HIGHER Float Sensors have saved me a couple of times but if the Optical Sensor cannot be deemed reliable, this may become disturbing. (If my Maxi tubing has been leaking/siphoning from time to time, then I shouldn't be quick to blame the Optical Sensor for not shutting off pumps, but there is still the issue of pumps sometimes not being turned on when they should be).

Thanks for helping!

 

[AZMSGT]

I think it's unlikely that the water can siphon through the maxi doser head. The wheels pinch off the tubing when it's in a stopped position. This should do two things. 1. Stop a siphon 2. Keep the liquid in the lines till the next time the system calls for fluid.

You could test it, take the line out and put it in a bucket. Run it then monitor it for a few hours and see if the water level goes up.

I had an elaborate ATO AWC system using the sensors too. Honestly It would drive me mad regularly. SO I simplified things to a measured, simultaneous Out and IN awc. Basically I set the AWC to remove a specific amount and add back a specific amount. Doing things this way requires calibration of the pumps. No big deal and easy to do.
Also this tends to maintain a steady level in your sump. I then use the ATO single sensor option to keep the sump topped off. It's been working well for me over the last 3-4 weeks.

 

[Dr. Jim]

I think it's unlikely that the water can siphon through the maxi doser head. The wheels pinch off the tubing when it's in a stopped position. This should do two things. 1. Stop a siphon 2. Keep the liquid in the lines till the next time the system calls for fluid.

You could test it, take the line out and put it in a bucket. Run it then monitor it for a few hours and see if the water level goes up.

I had an elaborate ATO AWC system using the sensors too. Honestly It would drive me mad regularly. SO I simplified things to a measured, simultaneous Out and IN awc. Basically I set the AWC to remove a specific amount and add back a specific amount. Doing things this way requires calibration of the pumps. No big deal and easy to do.
Also this tends to maintain a steady level in your sump. I then use the ATO single sensor option to keep the sump topped off. It's been working well for me over the last 3-4 weeks.

Which sensor are you using for ATO: Optical or Float? (GHL?) If GHL Optical, have you had any problems where it hasn't responded?

I, too, use the simultaneous OUT/IN for AWC which has been working fine.

I think the problem with figuring out if the Maxi is "leaking"/siphoning is that, if it is leaking, it is not leaking all the time. I am wondering if there are certain positions where the wheel stops that may allow the leak. I'm saying this because this morning, when I found my sump level high, I saw an air bubble slowly passing down the tube from the Maxi. Unfortunately, I didn't think fast enough. To make sure I had my tubes labeled correctly, I turned on the Maxi for a second to see which tube water came out. But by doing so, I changed the position of the pump wheel. I should have followed the tube with the moving air and affirm that water was dripping out of that tube. I had my chance and blew it!

 

[AZMSGT]

I’m using 1 optical sensor. I was trying the two sensor version but I didn’t like the space between them.

 

[Dr. Jim]

I’m using 1 optical sensor. I was trying the two sensor version but I didn’t like the space between them.

Have you (or anybody) run into problems with the Optical Sensor not responding when it should?

 

[AZMSGT]

What I found was when using the high-low sensors, when the water level was well below the low sensor the ATO system would stop adding water in. It was a weird thing. I got so frustrated with it I went to simpler ways of doing things.

 

[Dr. Jim]

What I found was when using the high-low sensors, when the water level was well below the low sensor the ATO system would stop adding water in. It was a weird thing. I got so frustrated with it I went to simpler ways of doing things.

CONCLUSION AND WARNING FOR OTHERS:

After more thought AND looking back at the Maxi Manual, it is clearly evident that water CAN siphon thru the tubing. One "proof" was the fact that I saw an air bubble traveling DOWN the tubing coming from the Maxi's "out" tube (when the Maxi was not running). The only way that an air bubble can travel "against gravity" would be if the water column in the tube is moving, of course.
But a better "proof" is from simply looking at the Manual....(duh).....which I should have done before I started this thread, so I apologize. But this may come in handy for anyone else who may have missed this important detail in the Manual:

"In order to prevent backflow through the siphon effect, the dosing tube in the tank should not reach directly into the aquarium water on the pump side."

My Maxi is positioned above the "LIquid Level" (RO/DI tank) as shown but the outlet hose is not going to the tank but to the sump which is BELOW the "Liquid Level" thereby allowing the possibility of a siphon effect. (I now have the outlet tube redirected as shown in my photo in first post).

My GHL equipment has only been in use for 2 months and I'm surprised that this problem has taken so long to crop up (but in retrospect, I have reason that it has happened once or twice in the past and I probably erroneously blamed the sensors for failing).

I'm SORRY if I wasted anyone's time reading this. ….but hopefully someone may benefit.

 

[Member No 1]

That's all and good, but how do you expect to use the AWC feature if the suction side isn't in the water.
I have had a DOS (same pump head) set up for 2 years, below the sump in my basement, but yet above the ATO and NSW barrels. Never had an issue.
I'll be setting up a Maxi to replace the DOS in a few weeks, and I'll monitor to see if I see any siphoning.

 

[Dr. Jim]

That's all and good, but how do you expect to use the AWC feature if the suction side isn't in the water.
I have had a DOS (same pump head) set up for 2 years, below the sump in my basement, but yet above the ATO and NSW barrels. Never had an issue.
I'll be setting up a Maxi to replace the DOS in a few weeks, and I'll monitor to see if I see any siphoning.

For your AWC: if the pump is below the sump and above the NSW, then obviously there will be no chance of siphoning when you pump in new water as long as the outlet tube is not underwater in the sump. (This would be essentially exactly what is shown in the diagram above).
The question would be: How are you removing the "old" tank water to avoid a potential siphoning problem? I would think that the "waste" outlet tube from the pump would have to run back upstairs above the sump water level to be drained in order to avoid the siphon risk.

 

[Jaebster]

For your AWC: if the pump is below the sump and above the NSW, then obviously there will be no chance of siphoning when you pump in new water as long as the outlet tube is not underwater in the sump. (This would be essentially exactly what is shown in the diagram above).
The question would be: How are you removing the "old" tank water to avoid a potential siphoning problem? I would think that the "waste" outlet tube from the pump would have to run back upstairs above the sump water level to be drained in order to avoid the siphon risk.

In my build, I'm going to have a separate "drain" PVC line going down in to the garage, my future AWC RO drain line will empty in to the PVC drain at about tank level, along with other drain RO lines i.e. KHD drain, IOND drain. That way, there is an air break and the RO tubing doesnt need to be long and far below the sump level that the gravity pulls water from the sump.

 

[Member No 1]

For your AWC: if the pump is below the sump and above the NSW, then obviously there will be no chance of siphoning when you pump in new water as long as the outlet tube is not underwater in the sump. (This would be essentially exactly what is shown in the diagram above).
The question would be: How are you removing the "old" tank water to avoid a potential siphoning problem? I would think that the "waste" outlet tube from the pump would have to run back upstairs above the sump water level to be drained in order to avoid the siphon risk.

The DOS, NSW are in the basement, the OSW drains to the basement. Never an issue with siphoning.

 

[Dr. Jim]

It seems very likely that siphoning occurrences are not very common. I didn't have a problem up until now (which has only been 2 months). But, because it DID happen to me, and because the Maxi Manual warns about it, it certainly makes sense to me to set it up as the Manual, jaebster and I have suggested. I want peace-of-mind when I go away. Two gallons of water siphoned during the night last night. If I was away for a week, that would be about 40 gallons of RO/DI water that would have siphoned into my sump (which only has room for about 15 gallons.....and this is on a 40 gal tank). It may never happen again but I won't take the chance. It may be true that this may be a rare occurrence, but all it might take is for the Maxi wheel to stop in a certain position that somehow allows seepage. For most, it would probably be a pretty simple preventative step to avoid a disaster.

 

[Member No 1]

It seems very likely that siphoning occurrences are not very common. I didn't have a problem up until now (which has only been 2 months). But, because it DID happen to me, and because the Maxi Manual warns about it, it certainly makes sense to me to set it up as the Manual, jaebster and I have suggested. I want peace-of-mind when I go away. Two gallons of water siphoned during the night last night. If I was away for a week, that would be about 40 gallons of RO/DI water that would have siphoned into my sump (which only has room for about 15 gallons.....and this is on a 40 gal tank). It may never happen again but I won't take the chance. It may be true that this may be a rare occurrence, but all it might take is for the Maxi wheel to stop in a certain position that somehow allows seepage. For most, it would probably be a pretty simple preventative step to avoid a disaster.

I do understand your argument for doing as the GHL manual states, but I don't understand why after 2 months you are having a problem. The Maxi dosing heads look way to familiar to the DOS heads, and people have interchaged them, so I'm thinking the same company makes and rebrands them. Not sure if there were any design changes, but the early DOS heads were notorious for cracking on the inside. I had several do it. Have you taken your Maxi dose heads off and inspected them? I still believe you have another issues causing the back siphon.