What's clogging my chlorine feeder output tubing?

[DrewLG]

I've been using a HASA liquid chlorine feeder for a few weeks. Something is precipitating out of the liquid in the tank and settling at the bottom -- there's already a half-inch layer of it. The HASA patent says that this is NaCl, but I can't test it because I don't want to disturb the chlorine layer. Regardless, HASA says it's expected and doesn't hurt anything.

But here's my problem: Something is also precipitating out of solution in the outlet tubing from the feeder. The tubing is only 3/8" OD, and the flow through it is gentle and for only 5 hours/day, so the precipitate eventually clogs the hose.

I see no similar precipitate elsewhere in the pool plumbing (or in the pool), although of course the rest of the plumbing has MUCH larger cross-section and flow rate.

The precipitate is white. I thought it might be the same salt that's accumulating at the bottom of the tank, but vinegar reacts with it. Unfortunately, I don't know anything about chemistry, so the only idea that that reaction gave me was calcium carbonate.

My pool water CH is 500. Does concentrated liquid chlorine make dissolved calcium fall out of solution somehow? What could this precipitate be?

 

[duraleigh]

I could never solve that salt precipitation issue (clog) so stopped using my HASAchlorine feeder some years back. I cannot remember the details but I went through quite a bit of effort and finally admitted defeat,

 

[JoyfulNoise]

It’s likely a mixture of salt and calcium carbonate scale. Liquid chlorine has a very high pH and when the pool water layer comes into contact with the liquid chlorine layer, calcium will precipitate.

Please post water test results for you pool water.

 

[DrewLG]

It’s likely a mixture of salt and calcium carbonate scale. Liquid chlorine has a very high pH and when the pool water layer comes into contact with the liquid chlorine layer, calcium will precipitate.

Please post water test results for you pool water.

Thanks! That makes sense; my CSI is high at 0.66.

Test results from the brand-new reagents in the TF-Pro kit I just received:

• FC: 4.5
• CC: 0
• pH: 7.8
• TA: 190
• CH: 400
• CYA: 50
• Temp: 79F

I've added muriatic acid to cut the TA, and now I'm aerating to bring pH back up from 7.0.

 

[JoyfulNoise]

Thanks! That makes sense; my CSI is high at 0.66.

Test results from the brand-new reagents in the TF-Pro kit I just received:

• FC: 4.5
• CC: 0
• pH: 7.8
• TA: 190
• CH: 400
• CYA: 50
• Temp: 79F

I've added muriatic acid to cut the TA, and now I'm aerating to bring pH back up from 7.0.

Inside the HASA tank at the interface between the water and the liquid chlorine the pH is closer 12.5. That means your CSI is way over +2.0 which will make any calcium in the water turn into calcium carbonate since there is also ample TA in the water (which is mostly bicarbonate). So the tank will develop a layer of calcium scale and the water that is drawn into the feed line for the pool will also develop scale and eventually plug up. This is known problem with the Liquidator setup. All you can do is watch it and clean the tank and tubing as needed.

 

[DrewLG]

Inside the HASA tank at the interface between the water and the liquid chlorine the pH is closer 12.5. That means your CSI is way over +2.0 which will make any calcium in the water turn into calcium carbonate since there is also ample TA in the water (which is mostly bicarbonate). So the tank will develop a layer of calcium scale and the water that is drawn into the feed line for the pool will also develop scale and eventually plug up. This is known problem with the Liquidator setup. All you can do is watch it and clean the tank and tubing as needed.

Ah, so the CSI of the pool water isn't really a factor. Calcium carbonate is diffusing up from the interface into the poolwater layer, then that saturated water is being pulled into the outlet tubing where the calcium carbonate comes out of solution, right? And the fact that the water stands motionless in that tubing for most of the day probably doesn't help either.

Hmm, I wonder whether I can flush the output tubing automatically:

The output from the Liquid Feeder goes to the input side of the filter pump, so water gets pulled from the upper layer in the feeder whenever the pump runs. But the input to the feeder comes from the pool return, AFTER the pool/spa return valve -- so fresh water is pushed into the feeder when the pool is running, but NOT when the spa is running. Because the feeder tank's inlet and outlet are both near the top of the tank, I can remove a couple inches of chlorine- and calcium-carbonate-infused water from the top of the tank by switching to the spa, then fairly rapidly refill that empty space at the top with fresh water by switching back to the pool.

So at the end of my daily pump schedule, would it make sense to try to get a slug of new fresh water at the top of the feeder tank, then let that fresh water get pulled into the outlet tubing, then stop the pump? If I can actually do that, would the relatively fresh water (without much chlorine or calcium carbonate yet) in the outlet tubing tend to keep that tubing clear?

 

[Chuck_Davis]

I've been using a Liquidator for years. I have a layer of "crud", maybe 0.5-1.0" on the bottom, including "plates" I've scraped off the sides. It doesn't seem to hurt anything so I've never bothered to clean it out. Hasa told me that some sort of (flat-bottomed?) scoop on the end of a stick could be used if I wanted to remove the precipitate.

My tubing does clog up periodically, however. I came up with a cleaning routine that turned out to be the same as Hasa's own field tech uses. Hasa recommends using a 5:1 diluted acid solution for periodically cleaning the floats. (Always add acid to water when diluting.) Once a year I disconnect the tubing at the outflow side of the Liquidator and stick the tubing in the jug of dilute acid with the pump running. Within 15-30 seconds the tubing (and flowmeter) are clean. I ignore the chlorinated water running from the Liquidator while the tubing is disconnected, but if you have a third hand available they could just stick their finger over the connector.

YMMV depending on your water chemistry. If your tubing is clogging frequently, one idea would be to plumb in a Y-valve with a permanent connection to a jug of 5:1 diluted acid.

 

[Chuck_Davis]

Do you have the original Liquidator or the new Liquid Feeder? I'm considering replacing my elderly Liquidator with a Liquid Feeder, and would appreciate any information that you might have.

(My suggestion for cleaning the tubing might have to be adapted for the Liquid Feeder.)

 

[DrewLG]

If your tubing is clogging frequently, one idea would be to plumb in a Y-valve with a permanent connection to a jug of 5:1 diluted acid.

Chuck, thank you! That's a fantastic idea. I'm ordering parts from Hope Direct right now.

 

[Chuck_Davis]

Glad I could (hopefully) help.

I worried a bit about my spider gasket, since I'm injecting the acid upstream of the multi-port valve, but since I only have to clean the tubing once a year it hasn't been an issue. If you are having to clean your tubing frequently you might try a more dilute acid mixture and let it run through a little longer.

What is your opinion of the new Hasa Liquid Feeder?

 

[DrewLG]

Do you have the original Liquidator or the new Liquid Feeder? I'm considering replacing my elderly Liquidator with a Liquid Feeder, and would appreciate any information that you might have.

I have the new one. It's nice. Once I solve the clogging problem, it'll be perfect.

I've got it plumbed into the pump-strainer drain plug and the pool return after the pool/spa valve (so it won't over-chlorinate when the spa is running at high pump speed for hours). They supply tubing-to-NPT compression fittings for those connections, but I replaced them with Parker TrueSeal fittings with integrated ball valves: Polypropylene Ball Valve - VMC Male Connector TrueSeal Ball Valve | The Hope Group

There's an inch-thick layer of precipitate at the bottom of mine, too; it formed the first day but hasn't grown. The tank has a drain valve with a garden-hose fitting that I hope will make it easy to clean if necessary.

I've only had the thing for a month or so, but I'll answer any questions I can.

 

[Chuck_Davis]

Thanks for the link on the ball valve. If I upgrade I may replace the fittings that I got at the boy toy store.

Where were you able to buy your Liquid Feeder? I don't have a local retail dealer, and the two online vendors that I've been able to find are pretty pricey.

 

[1poolman1]

I've been using a HASA liquid chlorine feeder for a few weeks. Something is precipitating out of the liquid in the tank and settling at the bottom -- there's already a half-inch layer of it. The HASA patent says that this is NaCl, but I can't test it because I don't want to disturb the chlorine layer. Regardless, HASA says it's expected and doesn't hurt anything.

But here's my problem: Something is also precipitating out of solution in the outlet tubing from the feeder. The tubing is only 3/8" OD, and the flow through it is gentle and for only 5 hours/day, so the precipitate eventually clogs the hose.

I see no similar precipitate elsewhere in the pool plumbing (or in the pool), although of course the rest of the plumbing has MUCH larger cross-section and flow rate.

The precipitate is white. I thought it might be the same salt that's accumulating at the bottom of the tank, but vinegar reacts with it. Unfortunately, I don't know anything about chemistry, so the only idea that that reaction gave me was calcium carbonate.

My pool water CH is 500. Does concentrated liquid chlorine make dissolved calcium fall out of solution somehow? What could this precipitate be?

If you are talking about the Liquidator, this is an on-going issue with those feeders. There seems to be no real solution other than to allow the chlorine to get used up and clean the tank and lines (coat-hanger wire works great). The description of the working process is that only chlorine molecules will rise into the water above the layer of liquid chlorine and be drawn into the system. They never said anything, in any piece of literature that I read, about the precipitate left behind. Used them off and on for 25 years. It just becomes a part of the maintenance of the beast.

 

[DrewLG]

Glad I could (hopefully) help.

Uh, yeah. I cleaned the tubing using your suggestion, and the flow through it was so good that my pool's FC concentration went from 7 to 27 ppm in a day. Wow.

 

[JamesW]

If your tubing is clogging frequently, one idea would be to plumb in a Y-valve with a permanent connection to a jug of 5:1 diluted acid.

You don't want acid to make contact with any type of chlorine as it can create chlorine gas.

 

[JoyfulNoise]

If you are talking about the Liquidator, this is an on-going issue with those feeders. There seems to be no real solution other than to allow the chlorine to get used up and clean the tank and lines (coat-hanger wire works great). The description of the working process is that only chlorine molecules will rise into the water above the layer of liquid chlorine and be drawn into the system. They never said anything, in any piece of literature that I read, about the precipitate left behind. Used them off and on for 25 years. It just becomes a part of the maintenance of the beast.

Their description of what's going on isn't really accurate. Liquid chlorine is a mixture of sodium hypochlorite, sodium chloride (salt), sodium hydroxide (lye) and water. It is more dense than water and so in the tank, the LC gets loaded into the bottom through the long fill funnel. Because it is more dense than fresh water, it will stay there. Over time, the hypochlorite diffuses up into the intake water layer and basically creates super chlorinated pool water. I have never seen it measured, but I would bet that the draw water off the top of the tank has a measurable % of sodium hypochlorite in it which wold make it highly chlorinated (100's or 1000's of ppm FC).

However, because the LC contains both salt and lye, there is a precipitation issue. With the bottom of the tank constantly being filled with fresh LC, the amount of sodium chloride starts to build up. After a while, the salt concentration exceeds the solubility limit and salt starts to precipitate out of solution. Salt crystals start to grow and they will "climb" up the sidewalls and create all the flat pieces of crystals. The sodium hydroxide (lye) in the bleach easily diffuses into the upper water layer as well drastically raising the pH. Again, I've not seen it measured but the pH of that water layer could easily reach 12.5. At that pH, and calcium in the draw water will react with the carbonate alkalinity and cause calcium scale to form. That is the stuff that starts to clog up all the tubing and the float valves. Eventually, the liquidator just needs to be taken apart so all of the excess salt and calcium scale can be removed. water will dissolve the excess salt but the calcium scale requires acid.

My biggest beef with the system though is how it constantly feeds highly chlorinated water into the pool pump where it then gets sent through the filter. All other chlorinators operated by creating and supplying chlorinated water at the return side of the plumbing, usually as the last device before water goes back to the pool. By injecting highly chlorinated water into the filter, it is much more likely to form CC's and other halogenated chemicals because the filter is where all of the dirt and organics reside. Its really not a great way to chlorinate. But, it is what it is.

 

[DrewLG]

the pH of that water layer could easily reach 12.5. At that pH, and calcium in the draw water will react with the carbonate alkalinity and cause calcium scale to form. That is the stuff that starts to clog up all the tubing and the float valves. Eventually, the liquidator just needs to be taken apart so all of the excess salt and calcium scale can be removed.

Interestingly (and maybe disingenuously), the patent views the precipitation as a beneficial sequestering of that material from the pool water. Two of the claims relate to the collection and easy disposal (through the drain valve) of apparently undesirable sodium chloride.

By injecting highly chlorinated water into the filter, it is much more likely to form CC's and other halogenated chemicals because the filter is where all of the dirt and organics reside.

Is the high chlorine concentration necessary for that to happen, or does it also happen via the normal process of flowing lightly chlorinated water through the filter? I'm wondering whether I can tune the chlorine flow vs time to minimize the undesirable reactions.

 

[JoyfulNoise]

Interestingly (and maybe disingenuously), the patent views the precipitation as a beneficial sequestering of that material from the pool water. Two of the claims relate to the collection and easy disposal (through the drain valve) of apparently undesirable sodium chloride.


Is the high chlorine concentration necessary for that to happen, or does it also happen via the normal process of flowing lightly chlorinated water through the filter? I'm wondering whether I can tune the chlorine flow vs time to minimize the undesirable reactions.

Patents can claim whatever novelties they like, but it doesn't mean they are useful or effective. Plenty of things have been patented that are complete garbage. A patent is simply a right of intellectual property assigned to the patent holder, it says nothing about utility. In this aspect of calcium precipitation, the amount of material precipitated is likely insignificant to the total weight of calcium dissolved in the pool water OR added everyday via evaporation and refill.

As for CC formations, it is concentration driven. At low FC, many of the reaction rates of various noxious CC's are so low that it doesn't matter. But once you start increasing the concentration of chlorine in the water, reactions start to proceed much faster. There are CC's that are measurable on the FAS-DPD test and there are trihalomethane (THM) and disinfection by-products (DPB) compounds that are not measurable but still very dangerous. I'm reminded once of a post by a person who setup an intex pool with an SWG and let the SWG run at 100% output with no CYA in the water and covered the pool to warm it. The person then got into the pool and, within a few minutes, became very light-headed and nauseous. The measured FC was off the charts and beyond the ability of DPD test to measure (which means much more than 50ppm) and, because there was no CYA in the water, the FC was free to react with anything organic. It's likely the person was made ill by the formation of CCs and chloroform from the oils and organics on their skin.

So yeah, shooting highly chlorinated water into a filter can cause some serious issues. Whether or not they are measurable is not easily known. You could attempt to measure the FC of the outflow water from the liquidator and see if it you can dilute it to get a reasonable measurement.

 

[1poolman1]

New system may have a drain valve. Liquidator was/is "dump and refill." When I was actively servicing those systems I had a 1/4" stainless steel rod that I had ground a kind of cutting edge on to clear the tubing.

 

[Chuck_Davis]

You don't want acid to make contact with any type of chlorine as it can create chlorine gas.

I've never seen any signs of a reaction. I'd be surprised if a 30-second flush caused much of a reaction, especially since the acid is diluted before use. Next stop for any possible chlorine gas "burp" is the pool itself.