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Siphoning through a dosing pump?!?!

Dorfman

Dorfman

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I recently set up a peristaltic dosing pump and have the pump and dosing liquid (Vinegar/Vodka in this case) sitting on a shelf above the sump where the liquids are being pumped into (duh). Last night I was sitting there watching the dosing happen just to make sure all was working properly and when the dosing session was over I noticed drops continue out of the output hose into the sump. I had assumed bc of the way the pump works that the "rollers" in the pump head would pinch off the silicon tubing when not pumping and a siphon would not occur but apparently I was wrong.

Glad I didn't dump the whole bottle into my tank but really don't want to put the liquids on the ground below sump level. Anyone dealt with this before and come up with any innovative solutions (e.g. check valve...)?
 
Sounds like something is wrong with the pump rollers and/or tubing to me. If fluid can pass the rollers when off, it will be a problem no matter where you position everything (either dripping out into your tank or having air come back in the line so you aren’t dosing the expected amount). You could try putting the doser and dosing reservoir at the same level as the end of the tubing as much as possible to minimize the problem, but it will likely still be a problem.

Not all tubing works well with vinegar/vodka, so make sure you are using appropriate tubing (including the short segment of tubing inside the doser head that the rollers contact).
 
So I think I just figured it out. @JVU you were on the right track. It appears to have something to do with the viscosity of the vinegar/vodka (V/V) mixture. I went back and forth between pumping the V/V mix and water. V/V was leaking and water was not. Its hard to describe but basically the V/V mixture was sliding along the inner wall of the tubing and leaving air bubbles in the line every once in a while. This was allowing liquid to continue to leak from the line once the pump stopped. I had to do a manual purge of the line, charging the line with the V/V mixture in spurts, starting and stopping the pump a few times so the liquid would push the air bubbles through the line. Once all bubbles were out of the line, the V/V mixture seems to not be leaking out any more.

Moral of this story: Any time you change ANYTHING in your tank, no matter how seemingly simply or innocuous... observe... watch it work. These are complex systems and sometimes things don't work like you expect them to. Crisis averted!
 
xcaret said:
You can always install a check valve on the outlet to prevent that issue
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Yeah I still think for this particular liquid its not a bad idea, just not sure if they make a check valve compatible with silicon tubing or it I will need to engineer some Frankenstein tubing conversion.
 
Dorfman said:
Yeah I still think for this particular liquid its not a bad idea, just not sure if they make a check valve compatible with silicon tubing or it I will need to engineer some Frankenstein tubing conversion.
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KHG uses a check valve that looks like this. I bet there may be somewhere to buy one similar. If not I can help you get connected with the KHG guy to order some, in my experience with him it would be a reasonable price.
C09E90FF-00A4-4DC1-AC75-0BDDD70C5544.jpeg
 
Check valve is a good backup, but I would figure out the issue if I were you. If the tubing isn't pinching off completely, your dosing won't be accurate.
 
Meshmez said:
Check valve is a good backup, but I would figure out the issue if I were you. If the tubing isn't pinching off completely, your dosing won't be accurate.
Click to expand...

That's another nail hit on the head.
Tubing has to be specific for the head/s in many pumps.
I have a peri pump that has some silicone tubing; I figured it was the correct one since I bought it that way. When trying to pump fluid back in the transmission of a VW (they engineer those things so is hard for anyone to do their own maintenance); the fluid has to be pumped from the bottom.
Turned on the pump and it didn't pull any liquid. Lucky for me, I have another pump and that one had the correct tubing so I was back in business.
 
Ooooofffhhhh! So after a few weeks of no issues my dosing system drained about 40ml of V/V mixture into the tank last night on a slow drip siphoning from the supply through the pump into the sump. I think its just an issue of a bad bounce. Presumably, if the dosing pump rollers stop in a position where the line is not completely pinched off, and if you have the supply liquid above the recipient vessel (eg. sump in my case) then the liquid can slowly drip/siphon. Since this is the second time this has happened to me since hooking up the dosing pump and I almost lost some fish today due to lack of oxygen (had to place a powerhead half in / half out of the water to inject Ox into the water) I am going to suck it up and place the liquids I'm dosing below the drip line out of the dosing pump. Not the layout I was hoping for but after a day of PITA tank recovery, I guess its what I have to do.

Message for all new reefers/dosers: Just place your supply liquid below the injection site, siphoning is real, you cannot rely on your dosing pump to completely shut off supply.
 
Unfortunately, not all dosing pumps are the same.
Some have fewer rollers.
Some have a smaller roller contact area.
Some have crappy tubing.
All to save cost.
I don't know the specifics of Hygger, but since it is one of the lowest cost, my guess would be they are not the best.

A good pump should not really have that problem.
 
rygh said:
Unfortunately, not all dosing pumps are the same.
Some have fewer rollers.
Some have a smaller roller contact area.
Some have crappy tubing.
All to save cost.
I don't know the specifics of Hygger, but since it is one of the lowest cost, my guess would be they are not the best.

A good pump should not really have that problem.
Click to expand...
The old adage "Ya get what ya pay for" is usually true. I will pop off the pump mechanism cover some day when I am bored and post the pic to this thread so we can discuss what we think may be going on mechanically there which is causing the problem. Then other members considering a dosing pump can decide is the savings is worth the cost.
 
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