Chlorinator Residue

[bcool]

I'm using a Waterway ClearWater Chlorinator (off-line) with chlorine pucks I've been getting from my local pool store in 7 kg pails. I believe they source their chemicals from Sani Marc Inc.

The problem I've been having lately is a gummy residue inside of my chlorinator. I've tried dissolving it with acid (acetic and muriatic) but acid doesn't affect it. I've been able to remove it mechanically with a brush and soapy water but it recurred after 1 charge of chlorine (11 pucks) and the photos are 24 days apart.

I mentioned this to the pool store's manager who then followed-up with her sales rep. She told me that no-one has complained about this before and the sales rep feels that this may have been the result of using a department store brand of chlorine. I did use a pail (8 kg) of HTH chlorine pucks that I got from Costco a few years ago but I've been using the store's brand of chlorine since.

FWIW, I drain my pool down every fall below the jets to winterize it and we get enough rain here that I have to periodically lower the pool level during the summer. For make-up, I use water from my pond, filtered to 5 microns.

Does anyone know why this residue forms and what would be the best way to prevent it from re-occurring?

 

[Bama Rambler]

Easiest and simplest way to prevent it is to quit using the tablets. Switch to liquid and you won't have that problem any more.

It may help if you post a full set of test results.

 

[bcool]

Switching to liquid implies that all pucks are susceptible to this problem. My impression from talking to the pool store manager was the pucks they supply are so pure that none of their other customers have this problem.

I get the water tested weekly and have test results for pretty much every week this summer. What results are you interested in?

What liquid chlorine dispenser would you recommend?

 

[jblizzle]

Well, all pucks may not have THAT problems, but they certainly all cause OTHER problems ... like crashing the pH and TA, and worse building up the CYA until the chlorine in the pool is not high enough to prevent it from turning green.

Pool store testing is notoriously bad, so we put little faith in any of their numbers. If you want to understand your pool's chemistry, read Pool School a few times and get one of the Recommended Test Kits.

Most members just pour a little liquid chlorine / bleach into the pool every day. Alternatively, you can get the Liquidator or a peristaltic pump to automatically dose the chlorine for you.

 

[bcool]

I had my doubts about the accuracy of the store's test results as they appear to be using whatever test equipment provided by their chemical supplier (this year's equipment seems to be problematic and seems to be down as often as it's up). As long as they used the same test strips and scanner, I figure that results would at least be reasonably consistent.

Is there any chance that the CYA in the tablets is reacting with something in the water to precipitate as a gummy residue? If so, what could cause this reaction?

The Liquidator seems to be a reasonable alternative to my ClearWater chlorinator. I'm not sure how the operating costs compare but I can buy 10L of 12% Chlorine for C$5 and a 7 kg pail of the chlorine tablets cost me C$44.99+HST. I have had to add several pails of Alka-Plus and Calcium Chloride this summer.

I had a hard time killing the algae from my pool this spring (took several 20L jugs of chlorine) so I've been trying to be diligent about keeping the algae under control. As such, I've giving my pool weekly 250 mL doses of Super Algicide 60 (PolyQuat 60). The "poly" part of the chemical makes me wonder if the residue is some sort of polymer residue from the algaecide.

I was reading in another liquid chlorine feeder topic that the liquid dosing could cause calcium carbonate scale that forms in the output valve.

 

[linen]

I'm not sure how the operating costs compare but I can buy 10L of 12% Chlorine for C$5

That is a great deal...comes out to $0.12/oz of NaClO!

If I were you, I would start using tfp methods by manually chlorinating with that Liquid Chlorine. You may find you don't need the automation.

Is there any chance that the CYA in the tablets is reacting with something in the water to precipitate as a gummy residue? If so, what could cause this reaction?

I have never heard of cya causing that. Where are finding the residue?

 

[bcool]

Where are finding the residue?

The gummy residue is in my chlorinator (see photos in my first post).

I could manually dose with liquid chlorine but I would much rather have a feeder do it. If I have to do it every day manually, I think there would be many missed dosings. I have enough trouble remembering to do the weekly 10L shock.

 

[linen]

I have no idea on the residue, but it doesn't surprise me, afaik, those chlorinators tend to have issues.

No need to do a weekly shock if you follow tfp methods.

Once folks on here get to understand their pools chemistry, they can often add bleach every two days verses 1...but that depends on the pool and the pool maintainer. I shouldn't talk, I have a swg that takes care of my chlorine for me...but I started with manual dosing and learned pool chemistry that way.

 

[CaOCl2]

It's looks like the binding agent they use when manufacturing (compressing) trichlor pucks. Stearic acid if I recall, so the stuff doesn't stick to the moulds while they're compressed into pucks. Let me find the reference in my books somewhere, I'll write back. If I recall they recommended using Tide (or something similar, I'm not kidding) to clean it off, but like I say I'll post back shortly.

 

[CaOCl2]

Got it, it's from the book "Pool Chlorination Facts" by Lowry, seems that manufacturers mixed stearates in with the trichlor to make their tabletting equipment run faster. Stearates are a wax-like substance that are not soluble in water. Some manufacturers may still use them but most have switched to boric acid as a mold release lubricant. The author suggests using granular Tide and a brush or other non-metallic scrubber. He also suggests using TSP. Use rubber gloves and goggles. Work outside with lots of ventilation. Rinse water may contain some chlorine so be careful of the run off.

 

[bcool]

That makes a lot more sense than the residual effect of the HTH trichlor tablets I used a few years ago.

Would there be any chance that stearates could could contributing to the black scum problem I've also got posted here?

For the time-being, I'm going to continue using the ClearWater chlorinator. Does anyone have any recommendations for stearate-free trichlor tablets?

 

[duraleigh]

I could manually dose with liquid chlorine but I would much rather have a feeder do it

We all would. The pucks have side effects other than the black goo that you do not appear aware of.

Please read "The ABC's of Pool Water Chemistry" up in Pool School.

What is your CYA test result?

 

[bcool]

I had a look at Pool School and read through "The ABC's of Pool Water Chemistry". I was aware that using the trichlor pucks causes a build-up of CYA, which has an affect on free chlorine. As I have to drain down the pool for winterizing, every spring I have to add granular stabilizer through the skimmer. I've also had to dump probably a 1 ft of water this summer (subsequent to CYA addition) due to rainfall.

My latest pool store chemical report shows the following:

Free Chlorine - 4.5 ppm
Total Chlorine - 4.5 ppm
Combined Chlorine - 0 ppm
pH - 7.4
Adjusted pH - 7.4
Total Alkalinity - 115 ppm
Adjusted Alkalinity - 115 ppm
Stabilizer - 60 ppm (IIRC - measured with reagent and sight glass)

I wasn't aware that the CYA causes pH and Total Alkalinity to drop but that might explain why I've been adding Alka-Plus. Are there any other side effects of CYA?