I was looking at my plaster's (Premix Marbletite) chemistry recommendations and here is what they recommend

POOL WATER CHEMISTRY
WARRANTY CLAIM PROCEDURES
It is necessary for the longevity of your pool finish and as a condition of this warranty, that the
following chemical guidelines and Sequestering Agent® levels must be followed and maintained:
Sanitizer levels must be maintained in accordance with the manufacture’s specifications of the
sanitizer you are using. (Example: Free Chlorine = 1 - 3ppm)
pH 7.2 - 7.6
Total Alkalinity (TA) 80 - 120 ppm
Calcium Hardness (CH) 200 - 400 ppm
Cyanuric Acid 40 - 60 ppm
Sequestering Agent 10 - 12 ppm (6oz. Per 10,000 gal of water)
Salt Water pools Lower pH to 7.2 weekly (Very Important)
Use Sequestering Agent for salt water pools
Pool fill water containing high levels of metals may need to be pre-treated and filtered before being added to your pool. Do Not stop the water while the pool is filling. If adding additional fill hoses, add to the deep end of the pool only. The initial process, including start up chemicals, should be done by a pool professional. This may take several days. Afterwards balance the pool water to the above noted water parameters. Check the pH several times per week for the first few weeks and add pool acid pre-diluted to the deep end of the pool to lower the pH to 7.0-7.2 range or lower if needed. Never allow the pH to rise above 7.6 during the first 30 days. Brush the pool daily for the first 30 days, then as needed. To help prevent metal stains and scaling of the finish and to up-hold your
product warranty, you must add the proper amount of Sequa-Sol® or any leading brand of
Sequestering Agent weekly. Noted above) After the first 30 days, check the pool water routinely at least once a week or more often and keep the water balanced to the above noted water chemistry parameters. For Salt water pools: do not add salt to the pool for the first 30 days. Be sure to add pool acid weekly and lower the pH to 7.2 ppm. No pool cleaners without brushes or vacuums with wheels for the first 30 days. Do not add Calcium for the first 60 days; then only if it is below 200 ppm.


I remember putting in some sequestering agent in the beginning however I have not added any more. I would like to know the pros and cons for using this chemical.
Thanks in advance

Sequestering agents are designed to keep metals in suspension so they don't tint the water but most importantly they prevent the metals from staining surfaces. I'm sure that's why your plaster mfg requires them. They don't want a customer service issue cuased by staining because of metals.

Thanks bama, the pool is crystal clear and I see no evidence of staining. Would it be safe to not use a sequestering agent? If I was going to use it how often should I Use it and how do you test to see if it is working? All thoughts and experience are welcomed

While it would certainly be safe not using it, the problem comes IF you have a problem. Then the mfg might deny warranty because you didn't follow their guidelines. While it should be only the case if there is discoloring, etc. of the plaster we all know how mfg's use all kind of things to deny warranty. There is usually a test with the agent for testing the dosage.

HEDP Sequestrant can save you a lot of headaches down the line. It helps prevent calcium deposits and will ward off staining of your surface. I don't have copper or iron in my fill water BUT I have copper staining on my blue plaster from using Ionization for years, that threw copper into the water constantly. Copper staining is virtually impossible to get rid of without removing a lot of the plaster with acid washing. Sometimes that won't even work (my case).

Iron......... I don't have iron in my fill water but it gets into the pool from our dust, sand, and silt. If I don't use sequestrant, it will stain the remaining white scale in a few days.

See this post where I recently asked about the safety using HEDP with animals drinking the water:

http://www.troublefreepool.com/sequestrant-any-issues-pets-drinking-from-pool-t23344.html

The HTH Metal Control, purchased at Walmart is a good bargain @ $14-$15 per 32 oz bottle. For HEDP products you will see on the label these two important ingredients: Hydroxy Ethylidene, Diphosphonic Acid

I've been using it in my pool since last fall after doing an AA treatment. Sequestrant and never allowing the pH to go above 7.5 is actually loosening some of the white scale on my blue plaster. I help it, too, by brushing with an aluminum brush. The copper stains may be lightening a bit but that observation might be a result of wishful thinking. I had heavy scaling on the steps. When the pool was empty for an acid wash in 2008 I spent two hours with an angle grinder, using concrete disc to remove the scale on just one step. I had to stop that work due to an injury. The scale has been releasing slowly on the top two steps. Top step had some copper staining that glazed over the surface of some of the scale making it much harder to remove. This week I spent some time really going after that with a small aluminum brush and finally got it to release.

Who wants to do this when it can be prevented?

I use more than maintenance dose called for on the label; 2X to 3X dose called for, weekly, with an addition of a whole bottle once a month or so.

Better to Prevent than to Treat

gg=alice