New member, first question.

[helzerr]

Hello fellow TFP members,

I've been lurking on the forum for about a year now (since I purchased a home with a pool), and just recently decided to take matters into my own hands instead of blindly following the previous owner's regimen and pool store advice. I am now the proud owner of a TF-100 test kit and equipped with knowledge gleaned from the forum and the "Pool School"

I've decided to forego the Trichlor pucks / floater, regular treatments with polyquat 60, etc. and switch to liquid chlorine only. To achieve some measure of automation, I installed a HASA Liquidator. This has been working well for me for the first week, but today the first problems struck...

Here are my most recent water parameter measurements: FC 6.5, CC 0.5, pH 7.5, TA 130, CH 490, CYA 70

It seems the high CH of my (re-plastered a year or two ago) pool is gunking up the Liquidator's works. The flow meter and check valve from the "out" valve to the pool suction are both clogged with white "granules" which I assume are scale? I've since added 1.5 qt MA to reduce the pH and TA - what else can I do to help the Liquidator cope with the high CH? Will I ever be able to enjoy the automation of the Liquidator, without frequent servicing of the plumbing to remove scale? Is my only option a water change to reduce CH? Even the central-Florida fill water is pretty hard right out of the faucet. I've checked, but didn't see anyone offering pool RO services here.

Thanks in advance for any advice.

 

[chem geek]

Welcome to TFP!

Your TA is too high and that will tend to make the pH go up as well. Since your CH is also higher, your current readings give a Calcite Saturation Index (CSI) of roughly +0.3 depending on temperature. A positive CSI says that the formation of calcium carbonate scaling is possible and that is what you are seeing. If you were able to get your TA down to 80 ppm or even 70 ppm via the acid addition with aeration at low pH process (see how to Lower Total Alkalinity), then the CSI would drop to close to zero. Or as you point out you can lower your CH level but to achieve the same effect as the TA drop you'd have to lower the CH to around 200-250 ppm so that's a lot of dilution.

When using The Liquidator, it's best to keep the CSI on the low side so even slightly negative if necessary. The reason is that the pH coming out of The Liquidator is higher than in the pool due to the hypochlorite source of chlorine so the CSI will be higher there and therefore more likely to form scale.