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Tower Cap duckbill check valve stuck shut

The problem is likely that your duckbill check valve has ‘sticky lips’ causing the valve to be stuck shut.  This causes a vacuum to form in the electrolyzer (when it is shut off and cools down) which sucks water up (called backfilling) from the humidifier and often from the Drinking Water Bubbler to the Humidifier… And causes the AquaCure to over-fill.

This is USUALLY caused by lye crystals forming on the duckbill lips, which is usually prevented by using the syringe to fill the AquaCure through the duckbill check valve on the Tower Cap.  This is one of the many reasons that I tell people to fill the AquaCure using the syringe through the duckbill, so it get’s ‘cleaned’ every few hours.

The vacuum that sucks the water back into the electrolyzer (from the filter) is NORMAL, all electrolyzers form a vacuum when they cool.

But a vacuum is an issue because of the backfilling that would then also (naturally) occur.  Backfilling causes the electrolyzer to over-fill.

Most electrolyzers solve this issue by adding a check valve to the outgoing gas hose, to only allow gas/liquid to flow OUT of the electrolyzer but not IN.

But check valves can (and often do) fail (for many reasons) allowing the backfilling anyway.  Those check valves also cause a vacuum to be formed (and be held) in the electrolyzer. 

These check valves also cause a pressure drop of (usually) 0.5 psi, which means that the electrolyzer needs to be operated at 2.5 psi to have an output of 2 psi (lower pressure is safer).

So all considered, I chose a BETTER option, the duckbill.  This is what a duckbill valve looks like
The duckbill allows air to flow into the electrolyzer and prevents HydrOxy from flowing out, mitigating any vacuum and solving all the above issues.

We can test for check valve proper operation by putting a measured amount of water in the humidifier, running the AquaCure for an hour to warm it up and then allow it to cool with the gas output (from the humidifier) disconnected.  
If ANY water is missing from the humidifier when the AquaCure has cooled (about an hour) then the duckbill failed (stuck shut) and you have back-filling.  Sometimes you can actually see the water rising in the Tower Cap to Humidifier hose.

Obviously we have ONLY the humidifier hooked up during the test because the Drinking Water Bubbler would ‘refill it’ if there is a vacuum.  So the humidifier output must be open, so it can suck in air if it ‘needs’ it.
The duckbill valve ‘lips’ can get ‘stuck shut’ with lye crystals.  

It’s usually easy to fix with the ‘toothpick’ cure below… because once the duckbill lips have been released, they work fine.

The ‘fix’ is really simple.  Here are the DIY fix instructions:
You would need
1.  a toothpick and some olive oil.  

The duckbill is a low pressure one-way check valve specifically placed in that location to PREVENT a vacuum from forming inside the electrolyzer.

You need to thoroughly wash the duckbill, inside and out, then apply a very thin layer of olive oil onto the inner portion of the lips, using the toothpick.

That should prevent the lips from sticking and causing backfilling, if that is your problem.

Wash it first with a jet of pure water, then take a toothpick, wet it with olive oil (just enough to make it slippery because too much olive oil can ALSO cause the lips to get ‘sticky’) 
and gently insert it into the center of the duckbill (careful not to tear the lips), you should be able to slide it past the lips, clearing anything that is holding the lips shut.

You only need to open the lips, no need to stick the toothpick in more than ¼” past the lips.

That should fix the issue.  

Note: It might ‘over-fix’ the issue and the lips don’t stay shut like they should (resulting in a gas leak), the fix for that is to use the syringe to ‘suck backwards’ which will clamp the lips together.  Make sure there isn’t anything between the lips keeping them open.

If lightly lubricating the check valve lips DOES NOT WORK (Note that TOO MUCH oil can cause the lips to stick shut too), 
then you CAN add another duckbill check valve on the Tower Cap gas out fitting.
You’ll need a short adaptor hose to connect it to the gas output AND to file off the ridge so that the Tower Cap to Humidifier hose can fit onto the end of the check valve.

Note: I DESIGNED the Tower Cap system to have the AquaCure fresh water filled THROUGH the Tower Cap duckbill, so the duckbill would be ‘washed’ (cleaned of lye crystals) every time the AquaCure is filled, which is supposed to prevent lye crystal formation that would cause the lips to stick shut (or open).  

Further, the Tower Cap is NOT designed to be removed constantly to re-fill the AquaCure with water (the plastic threads and seal will wear out).  ONLY remove the Tower Cap for the 100 hour sludge cleanings.  Re-fill the AquaCure through the duckbill check valve.

Note: Some people ‘accidentally’ plug the duckbill check valve, thinking it’s just a pipe sticking out the side that would be a gas leak.  DO NOT plug (or cap) the valve.  Air MUST be allowed to flow into the AquaCure as the gasses cool down to prevent backfilling.

Note: If you’ve been removing electrolyte as the machine ‘overfilled’, you should add an ounce of lye to replace lye you took out when you were lowering the electrolyzer liquid level. 

To add lye you need to pour the electrolyte solution out into a container, mix in the additional lye and pour the electrolyte back into the AquaCure.  
NEVER just pour pure powdered lye down into the machine (it will set up like concrete and plug orifices)!

… “the overflow button is going off again and the bubbler is drained.” 

Then the problem was not fixed.  The check valve lips are still ’sticky’  This is actually a very rare problem, usually caused by people not filling the machine through the Tower Cap check valve as described.  As you can see, the valve needs to be kept clean to work properly.  But I’ve heard of a couple (out of thousands) that got sticky even with people properly filling the AquaCure through them.

In any case, the machine itself is not having any problem.  In your case the entire problem is the one valve on the Tower Cap.  And that problem is 100% ‘fixable’ with proper maintenance.  
In your case, it just has to be cleaned thoroughly, which should fix the issue in and of itself.  
The olive oil is just an additional procedure for those that don’t get the valve entirely clean.

In your case, since it ’stuck’ again, the answer is simple.  It was not yet clean.  It will function correctly once it is really clean.

Since your valve is being particularly sticky, here is some advice I’ve never given to anyone (because I’ve never needed to), to make sure it is REALLY clean.

it may help to (when you clean it this time) wash the inside of the Tower Cap really well with warm water and a bottle brush, concentrating on the check valve inner side.  

Do not use dish soap.  Dish soap can cause the valve to be sticky.  The lye IS an ingredient of soap, so no soap is needed to make it clean, just warm water.

Then squirt HOT (tap) water through the check valve a LOT, at least 10 times and up to 50 times.  
This should wash any lye off the inner lips of the check valve. Then clean and dry the Tower Cap and do the olive oil.  
The olive oil won’t stick to the inner lips if they are wet with water.  

Blowing dry air through the check valve (with the syringe) will help to dry it.  

And note that you only need a very THIN layer of olive oil, too thick creates it’s own problem.

Note that the issue ONLY occurs AFTER the machine is shut down.  As the hot gasses cool, they make the vacuum that sucks the water back (if the check valve doesn’t allow air in).  So the alarm would not ‘go off’ as you are sleeping (assuming you run the machine all night).

There IS the option of putting a check valve on the gas output of the Tower Cap as well, so that (in theory) the water would never suck back from the Humidifier.  This would (in theory) ‘fix’ your issue.  I’ve never recommended this before either, but again, I’ve never had a check valve ‘fail’ to function properly after being cleaned and properly lubricated.

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