Sequestrant?

[BigTallGuy]

I stopped into my local pool store today to see if they had any Salt Testing Strips. I was looking for the 10 minute variety as recommended by Waterbear and PoolSean. They didn't have anything but the 2 minute strips.

Anyway, we got to talking about SWCG's. The conversation went into the Self Cleaning aspects. Before I could almost get a word in edge wise, He tried to sell me a Calcium Sequestriant (not sure if I spelled that right). A bottle that looked like about a half gallon sold for over $35. The claim is, this stuff keeps calcium from binding together and thus not sticking to your plates in the SWCG. So far, I have had to clean my SWCG twice using good ol' Muriatic acid, so naturally, I declined the offer, but I am just curious and thought ChemGeek or someone might have a comment.

[kelemvor]

Was he talking about this stuff by chance? Jack's Magic Purple Stuff

[BigTallGuy]

Nope.

[waterbear]

There are some products that increase the magnesium hardness of the water because magnesium scale is "mushy" and rinses off easily. Perhaps that is what he is trying to sell you. Whether they work to prevent calcium scale i cannot say.
There are also some sequestrants that have a high chelation index for calcium which ,after all, is a metal. Most sequestrants have a high chelation index for iron or copper and, while they will sequester some calcium anyway, it is not what they are designed for. My feeling is that these calcium sequestrants are most useful in areas of extremely hard water where the only other options are trucking in soft water or reverse osmosis filtration yearly. They do not eliminate the calcium but do 'inactivate' some of it if applied on a regular basis (just like any other seqestrant) to minimize scale buildup.

Then again, it could just be more 'snake oil'.

If you could post the brand and name of the product and/or the ingredients perhaps we could tell you more.

AS far as the salt test strips, the fast strips are made by LaMotte and the slow strips are made by AquaChek (Hach). I have never tried the LaMotte salt test strips but PoolSean did not seem thrilled by them. You can probably find them by mailorder on the 'net.

[Poolsean]

But then again, you can just test and ensure your water chemistry is balanced, according to the Saturation Index. This, along with the Self Cleaning feature of your salt system, should prevent calcium scale. As waterbear said, these chemical additives are more of a preventative product and can be quite an expensive option.

I love the guys at LaMotte and they have some excellent products. The quick read strips should (IMO) ONLY be used with a water sample under shade or indoor. So you can take a water sample then dip your strip once you're under shade, or dip the strip in the water, then go to a shaded location. If you do this in sunlight, my experience is that you have too short a window of opportunity to make your comparison. They are accurate enough, if you do it out of sunlight.

[BigTallGuy]

O.K. I didn't mean to take so long to respond, but I made it back into the pool store to see what the name of the product is. It is called SCALETEC, it is sold in 1/2 gallon bottles for around $35.

[kelemvor]

I see the manufacturer is forthcoming with information about it

Ingredient Information:
Components of this product comprises proprietary trade secret information.

http://www.easycarewater.com/files/S...20-%202011.pdf

In the Q&A they indicate you have to keep fc between 1.5 and 2.0ppm for 2-4 weeks. Depending on your CYA level, that might be a problem. For me to keep within 5% of CYA, I've got to be at 4ppm FC at CYA 80. Perhaps your swcg requires less cya, and 2ppm fc for a month would be OK?

[BigTallGuy]

The truth is, I have no intention of buying this product. As I stated earlier, I have only had to clean my unit twice since I bought it, and it is far too easy to take it apart and use a buck's worth of Muriatic Acid when it needs it.

I brought up the question as a bit of a heads up for others going to the Pool Store, and to get opinions from our Chemical Guys as to whether it would REALLLLLLLLY help reduce the calcium build up in a SWCG.

[chem geek]

There are at least four ways to reduce the amount of scaling at the hydrogen gas generation plate in saltwater chlorine generators. One is to have the Calcite Saturation Index (CSI) be more negative. The downside to that is that if it gets too negative then you risk dissolving plaster. Another way is to use 50 ppm Borates in the pool since this is a pH buffer that is particularly strong against having the pH rise so will effectively cut the amount of pH rise roughly in half in the SWCG. Another method, that is pretty much standard these days in SWCG systems, is to reverse polarity periodically since this largely reverses scale buildup. Another technique is to use a calcium sequestrant which is the topic of this thread. A calcium sequestrant effectively reduces the calcium concentration, but the calcium still shows up in a CH test so it is really lowering the CSI without your being able to know it. Depending on the sequestrant, it can also interfere with scale formation slowing the rate of formation down.

To me, using an SWCG that reverses polarity, using 50 ppm Borates, and targeting a slightly negative CSI (say -0.2) is a reasonable combination.