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Chlorine Injector Getting Scale Deposit


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I have an automatic liquid chlorine system on my pool. This works well most of the time but I am finding that the chlorine injector is getting a scale deposit of some sort, perhaps salt?, which stops it working. This used to be just an annual problem which was manageable but now seems to be happening more regularly. Any thoughts on how to stop this happening?

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Are you using The Liquidator or are you using a peristaltic pump? The Liquidator is known to have issues with calcium carbonate scaling because the pH of the chlorine solution is high at the outlet. The use of larger tubes and a modified valve are the solution (see this link about the 3/8" upgrade). If you are using a peristaltic pump, then perhaps your Calcite Saturation Index (CSI) is too high. You may need to lower your pH, TA, and or CH.

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I am using a Prominent Beta solinoid pump. The CSI is normally OK, I try to keep the pH at 7.4 but it tends to raise but is kept below 7.8 at all times. TA is normally reads 80 but is lower than this allowing for CYA which is 60, however, TH is about 400 which is higher that I would like but think I am stuck with it really. The 'scale' is very white and very soft which is why I wondered if it is salt. The injector is just a none return valve so dosent stick out into the water flow very well so I am wondering if I might be better finding something with some form of pipe on it that will stick out into the center of my 50mm supply pipe.

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Total Hardness? Are you using test strips? You should be using a proper test kit such as the Taylor K-2006. You need to test Calcium Hardness, not Total Hardness, and test strips are generally not accurate especially for some of the tests (depending on manufacturer of the test. So your CSI may in fact be too high.

As for injection, you should look at a Mazzei Venturi injector.

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Forgive me it is CH I'm measuring, I have a Lamotte 7022 as we cant get the Taylor kits in Europe, which means my CSI is fine.

I hadn’t thought of using a venturi injector as these are primarily designed to 'suck' fluids but I guess it should work with a solenoid metering pump. The plumbing would be a challenge in the confined space I have though, particularly if I need to have a flow control valve to divert flow through the venturi. The other issue is that this will add new potential points of failure within the plumbing which, as I am not always in residence, I would like to avoid if possible.

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I'm sure you shouldn’t/can't do this BUT.....is it feasible to add muriatic acid to liquid chlorine? I only ask as I regularly need to reduce my pH so if I could work out the dosing I could add muriatic acid to my chlorine and pump it at the same time. Not only would this help me keep my pH stable but it would reduce the calcification on my injector.

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Ah, Just been reading up on this and it seems it creates Chlorine Gas, so I guess you shouldnt do this unless you are in a war zone and even then you will get done for crimes against humanity, that will be a no no then!! Shame it looked like a neat solution for a few seconds!

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Yup. Never add acid to chlorinating liquid or bleach since that produces chlorine gas. People typically meter chlorine and acid separately. Note that if you are using chlorinating liquid or bleach that is high quality (not too much excess lye in it) then if you keep your TA lower (definitely no higher than 80 ppm but maybe 70 or lower) and target a higher pH then that reduces pH rise from carbon dioxide outgassing.

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