? chlorine injection causes precipitate ?

[000utback]

Hey, good morning. My well water runs about 20 gn hardness, 2 ppm iron, and slight sulfur odor. I add Cl to oxidize the S and Fe, then a contact tank, then a charcoal filter before the softener. A Stenner pump injects Cl solution (diluted laundry bleach) through a 1/2 T into the 1" water line. Plastic pex fitting. There is a buildup in the 1/2 T that has now totally blocked the Cl flow. I tried blowing the plug out with 100 psi air hose with no luck. Took the piping apart enough to apply a very stiff wire and still can't break through. Currently filled the fitting with 30% vinegar in hopes of dissolution.
Is this a known issue? Does hardness + Cl = precipitate? Is there hope that acid will dissolve it? I haven't found any other complaints about this. Interested in what's going on, and how to avoid it.
Right now I have rearranged the Cl injection route so it's a straight shot with no elbows. Thus I can remove the injection nozzle and apply the stiff wire to the blockage. If I ever get it out, I could imagine doing this ~annually to keep the path clear. If I ever get it out. I would rather not remove/replace the entire fitting. It's all pex, but still a mess and time consuming. It's deer season here, and we should all be out in the woods instead of putzing around in the basement.
Any feedback is appreciated.

 

[Reach4]

I am not a pro, but I have some thoughts and questions.

I think you are implying that the injector is after the pressure tank, and that the stenner pump pumps proportionally with flow, rather than pumping whenever the well pump is on.

I was getting some some white sediment in my chlorine solution tank (used only during regen) until I switched to topping that off with softened water. I assumed that was hardness (calcium). My iron is much less than yours. Why do you think the sediment blocking the path is due to calcium rather than the iron and sulfur precipitates?

Does your contact tank have a blow-off valve to flush out sediment?

Is your injection tee higher than the input to the contact tank? I would think that locating the injection to above and close to the contact tank input would make sense to me.

I have hope the vinegar will break down the precipitate, but I think it would need some flow or turbulance to bring unspent vinegar into contact with the blockage. Replacing PEX sounds easier than trying to unblock PEX.

 

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[000utback]

thanks for the quick comeback. Yes, I have a water meter and proportional controller for the Cl pump, after the pressure tank. There are outdoor hydrants between the well and the house, so I feared that linking the Cl pump to the well pump would over chlorinate the house water while I was washing cars or watering trees. (when we bought the house it had the tablet dispenser on the well head. I was glad to get rid of that).

The Cl injection is after the meter and a check valve (don't want Cl to ruin the meter) into the top of the 1" pipe (heavier Cl solution should sink in water), in a straight section of pipe. Then it goes through 4 elbows (good for mixing) into the contact tank. The injection is physically higher than the contact tank.

I'm guessing the buildup is Ca (hardness) because that's what happens on fixtures when the softener isn't working. The hard plug that I can see is dirty white. If sulfur and/or iron could be the culprit that's good to know.

I have bottom valves on the pressure tank, contact tank, and water heater that I should purge annually but honestly haven't for awhile. Now that I'm getting the system back to working like it should I'll certainly clean them out.

I set up the whole system, including rebedding the carbon filter, on my own after diligent internet research. At the time I couldn't find good help locally. It has worked great for many years. Like, 20 years. In that time replaced the carbon twice and iirc one other time the Cl injection point plugged.

The "experts" said the softener would take care of the iron, but it doesn't. When the Cl injection messes up (like when the Stenner peristaltic tube breaks) we get iron staining in the tub pretty soon. That's part of my confirmation that it's working. Likewise the sulfur odor is totally gone using the Cl / carbon, but is an issue if only the softener is working. It was really interesting learning about all that stuff. Like, a person can get any old water softener that still has a functional head unit, and fill the resin bed with whatever he wants based on his water issues, and it's fixed.

Anyway, yeah, just to say there will be many who say there's something incorrect on the set-up, but the results have been very good for a long time.

When I opened the valve to add more vinegar, I got a spurt of ____ that splattered the wall. Apparently the vinegar is reacting with the hardness (?), releasing CO2 and building pressure. But building pressure because the port into the 1" is still blocked. I'll freshen the vinegar regularly, but I'll prolly end up replacing the fitting as you say. Maybe this time use 1 x 1 x 1 so it takes much longer to plug up. And maybe a weaker Cl dilution in the meter pump, so it isn't as reactive.

 

[Reach4]

Yes, proportional injection is much better despite costing more.

The Cl injection is after the meter and a check valve (don't want Cl to ruin the meter) into the top of the 1" pipe (heavier Cl solution should sink in water), in a straight section of pipe. Then it goes through 4 elbows (good for mixing) into the contact tank. The injection is physically higher than the contact tank. If you put your maze into the horizontal plane, it might still mix things while reducing sediment build-up.

I think the clogging of your contact maze shows that the maze collects sediment.

I have bottom valves on the pressure tank, contact tank, and water heater that I should purge annually but honestly haven't for awhile. Now that I'm getting the system back to working like it should I'll certainly clean them out.

Some even have a timer-controlled valve to remove sediment. So maybe routinely run some water out as you do each solution tank refill? Dumping into a white bucket once in a while could help assess things. Your next purge water should be interesting. Maybe even take a photo.

And maybe a weaker Cl dilution in the meter pump, so it isn't as reactive.

I think you want a sampling port before the carbon, and use the residual Cl level to tune the injection. You might aim for 4 ppm free chlorine. Weaker solution would reduce chlorine, but so would a lower injection rate. How often do you refill the solution tank?

 

[000utback]

Yes, proportional injection is much better despite costing more.

I think the clogging of your contact maze shows that the maze collects sediment.

Some even have a timer-controlled valve to remove sediment. So maybe routinely run some water out as you do each solution tank refill? Dumping into a white bucket once in a while could help assess things. Your next purge water should be interesting. Maybe even take a photo.

I think you want a sampling port before the carbon, and use the residual Cl level to tune the injection. You might aim for 4 ppm free chlorine. Weaker solution would reduce chlorine, but so would a lower injection rate. How often do you refill the solution tank?

hey, thanks again for all the comments. This is all good stuff. In my case, the buildup only occurs right at the point where the 1/2" Cl injection line meets the 1" water line. The 1/2 side of the tee gets plugged with hard white deposit. So, yeah, not an issue of the piping afterwards or the Cl readings later.
I did soak the area repeatedly with vinegar and finally got it open enough to get the Cl injection to work again. Longterm I'll re-arrange the tee a bit so I can regularly keep it clean. Apparently there is indeed a reaction that precipitates something - likely hardness - in the immediate area of the confluence.
yes, when I set the system up I included sample ports before and after the contact tank and after the carbon filter. Water after the softener is sampled from the tap. I agree the 4 ppm is a good value.

quote: The primary chemical reaction for the formation of the precipitate is a double-displacement reaction:
Sodium hypochlorite is chlorine dissolved in sodium hydroxide solution and is alkaline.
Hard water typically contains calcium hydrogen carbonate formed by carbon dioxide reaction with limestone or chalk
CaCO3 + CO2(aq) + H2O -> Ca(HCO3)2 (aq)
The hydrogen carbonate ions can lose an H+ to alkali reprecipitating calcium carbonate
HCO3- (aq) + OH-(aq) -> CO3 2- (aq) + H2O(l)
Ca2+ (aq) + CO3 2-(aq) -> CaCO3 (s)

Yep, that's what it looks like to me!