If you want to really CYA it helps to learn the terms used in TFP posts ;-)


Jun 19, 2020
SE Florida
If you're a pool-care "newbie" (a.k.a. "noob") like me, and you've found the Trouble Free Pool (TFP) site and forums, you've probably come here to solve a problem relating to pool care [however, if you're looking for a way to improve your skills at playing billiards, sorry but this is the wrong site for that]. You might want quick answers to pool issues and don't have the inclination, interest and/or free time to spend reading all of the amazing background information for pool owners - but you should make the time and effort anyway, remember the old adage "The long way is the short way!" In wanting to get right to the heart of the matter and try to solve your particular pool problem you've probably jumped into the Forums and done a "search" for your specific issue, then you've started reading questions and answers looking for just the right solution for your own need. But... there's a slight glitch to this 'shortcut' attempt to skip [Pool] school - the Forums posts contain dozens of acronyms and initials with which regular users of this site have become familiar. You start wondering if CYA stands for "Cover Your [you know what]" or is OCLT short for the word "occult" and does your yucky green pool need an exorcism or does CSI mean you've committed a crime by not maintaining your pool properly and the Feds are on their way? Um, not quite.

Below is a list I put together for myself, a pool newbie, of common acronyms/initialisms used on TFP that had me a bit baffled at first. As I toured around the TFP site I found the site's Definitions and Abbreviations/Glossary page Glossary - Trouble Free Pool and a link to Further Reading - both great "quick" reference pages and they have a lot more info than what I've summarized here! Moderator kimkats also pointed out this excellent thread : TFPC for Beginners. You'll find that my list has info that appears elsewhere on the TFP site, and I added a few more short definitions to my personal list that weren't on the reference pages above.

I'll emphasize, this is a list I created for myself (not wanting personal attribution, just stating that this list is not endorsed or solicited or approved by TFP) as a quick guide and in no way is intended to take away from, correct, replace, circumvent, or diminish any of the excellent references and indexes on the TFP site - READ THEM first, and thoroughly! Again, this is my down-and-dirty "cheat sheet" of acronyms/initialisms, along with a few specific definitions, I came across while reading many posts in the forums while being virtually clueless about pools and pool maintenance, and am sharing this list FWIW (for what it's worth) to any other newbie who might find it useful for an "Aha!" moment when coming across these in the forums posts.

In creating my personal list I found the majority of the term definitions here within the TFP site, primarily used cut-and-paste to include that info, and also did searches online for other definitions when needed. Any notation of errors or needed corrections are welcomed as I'm no expert (have I mentioned, I'm a newbie???) and have relied on the expertise of others at TFP and on the Internet for this information, so it's quite possible I could have misinterpreted something(s) along the line.

I hope this list helps others like me who stumbled onto this site and went from "kicking and screaming" regarding doing my own pool maintenance to "Happy, happy, joy, joy!" at being able in short order to have a crystal clear pool with minimal time and money spent to keep it so.

I highly recommend reading the articles in the Welcome to the Pool School section of this site Pool School - Trouble Free Pool, either specific categories or click on VIEW ALL button and read each article, or get the ebook. The info provided in the Pool School section has been invaluable for answering many of my questions before I even thought to ask within the forums.

So here is my personal newbie's quickie 'cheat sheet' of Trouble Free Pool Acronyms/Initialisms/Additional Terms I seemed to see fairly often in posts:

-- ACI (American Concrete Institute)

-- AG (above-ground)

-- aggregate
A collection of units or particles into a body, mass, or amount - therefore an aggregate pool finish consists of an aggregate of materials, often ground and sanded river pebbles that are crushed and mixed into concrete.

-- ANSI (American National Standards Institute)

-- APSP (The Association of Pool & Spa Professionals)

-- ascorbic acid (vitamin C) Ascorbic Acid Treatment - Further Reading

-- Biguanide/Baqua (an alternative to chlorine) a.k.a. Baquacil, SoftSwim - referred to on this site as Baqua

-- bonding/grounding ABC's of Pool Water Chemistry - Trouble Free Pool
Bonding and grounding are two very different things that are often confused. Grounding serves two purposes. First, a ground conductor provides a low resistance path to conduct lightning strikes to the earth. Second, grounding provides a low resistance path for hot wire shorts to conduct enough power back to the main panel to trip the circuit breaker. Bonding is about making sure that any electrical current that is present around the pool goes through the bonding wire instead of going through you.

-- borate/Borax Borates - Trouble Free Pool
Borates stabilize pH making it harder for pH to change after the borate is introduced into the pool. For a low (acid) pH, borates (such as borax) can be added to raise pH (make the water more base than acid).

-- calcium scaling Calcium Scaling - Trouble Free Pool
If there is too much calcium in the water, calcium scale can form on the pool and in the plumbing

-- CalHypo (Calcium Hypochlorite) Calcium Hypochlorite - Trouble Free Pool

-- CC (Combined Chlorine) ABC's of Pool Water Chemistry - Trouble Free Pool

-- CYA (Cyanuric Acid) ABC's of Pool Water Chemistry - Trouble Free Pool

-- CH (Calcium hardness) ABC's of Pool Water Chemistry - Trouble Free Pool

-- Chlorine tablets/tabs (aka hockey pucks/pucks) such as TriChlor

-- Cement
A cement is a binder, a substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete

-- Colorimetric Measurement
Concentration measurement made by color comparison (in this case, pool water tests, such as seen with a pH test)

-- Concrete
A composite (compound) material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time

-- CSI (Calcium Saturation Index)

-- DE (Diatomaceous Earth)

-- DPD (N,N Diethyl-1,4 Phenylenediamine Sulfate)
DPD is the chemical responsible for indicating the presence of an oxidizer in the pool water, by showing a range of colors. DPD chemistry can distinguish the active sanitizer, termed free available chlorine. When DPD in either liquid or tablet form is added to a water sample, a pink color forms with an intensity proportional to the chlorine concentration (either free or total, depending on the step you're on in the procedure). The color of the treated sample is then compared to a set of color standards supplied by the test kit manufacturer. These standards may be encapsulated liquid dyes, colored plastic, printed colors on clear film, or printed colors on paper.

-- Dip-stick (also called "test strips", no this does not refer to your neighbor who hates pools <G>)
A (usually plastic, or stiff paper) strip that is made up of one or more chemical pads (see: reagents) which react (change color) when immersed in, and then removed from, a water sample.

-- drop test (or Drop-Count Titration Measurement - see: titrate)
A concentration measurement made by adding an indicator [see: indicator] to a water sample and then adding another reagent [see: reagent] drop by drop - as opposed to using a test strip/dip stick.

-- endpoint
With water test kits, the "endpoint" is when a final color change is reached and the color can then be compared to a scale or guide to indicate the test result or point at which to begin the next phase of the test.

-- FAS (Ferrous ammonium sulfate) see: FAS-DPD

-- FAS-DPD FAS-DPD - Trouble Free Pool
An FAS-DPD titration [see: titrate] is as simple as a test for total alkalinity or calcium hardness. A buffered DPD indicator [see: indicator] powder is added to a water sample and reacts with chlorine to produce the pink color characteristic of the standard DPD test. Ferrous ammonium sulfate (FAS) is then added drop by drop until the pink color completely and permanently disappears, signaling the endpoint [see: endpoint] of the reaction. To get the reading, the number of drops used to cause this color change is multiplied by the appropriate factor for the size of the water sample (supplied by the manufacturer).

-- FC (Free chlorine) ABC's of Pool Water Chemistry - Trouble Free Pool

-- gunite
Popular trade term for dry-gun concrete, while shotcrete is the common term for wet-gun concrete.

-- Hockey pucks (chlorine tablets, or puck, or tabs, or tablets)
A coined phrase that jokingly refers to the size and shape of an average chlorine/stabilizer tablet used in pools and spas

-- HP (horsepower, referring here to pool pumps)

-- IG (in-ground)

-- Indicator
A reagent [see: reagent] that changes color proportionally to the concentration of the parameter (type of test) to be measured or changes color quickly when a parameter to be measured has been altered 100% due to the addition of a chemical

-- liquid chlorine (regular bleach, sodium hypochlorite)

-- LSI (Langelier Saturation Index)

-- MA (muriatic acid)

-- magnetic stirrer/stirrer (the Speedstir is made by Taylor, who also makes pool water test kits)
A magnetic stirrer will thoroughly incorporate each addition of a reagent [see: reagent] in a test sample immediately rather than having to mix reagents and water samples by manually shaking or stirring the mixture. When using drops for water testing the magnetic stirrer helps to ensure each drop is well mixed so that drop-counting is most accurate.

-- metal/mineral
Metals are chemical elements such as iron or copper and have basic oxides, form positive ions, and are good conductors of heat and electricity - whereas Minerals refer to any of a class of naturally occurring solid inorganic substances with a characteristic crystalline form and a homogeneous chemical composition such as calcium, iron, potassium, sodium, or zinc (minerals do include metals) [whew, and I thought metal referred to loud music and mineral was what made my bottled water so expensive <G>]

-- MPV (Multi-Port Valves)

-- MSDS (Material Safety Data Sheet)

-- NPC (National Plasterers Council)

-- OCLT (Overnight [Free] Chlorine Loss Test) Perform the Overnight FC Loss Test (OCLT) - Trouble Free Pool

-- OP (original post/poster) - for anyone who's first experience with online forums (fora?) is on this TFP site, or you avoid anything having to do with "social media" and/or texting (you brave soul, choosing to not follow the herd over the cliff <G>), you might not have come across these initials before. You'll see references to OP now and then when someone's responding to the original post/poster.

-- OTO (OrthoTOlidine, also OT)
Used to analyze chlorine levels and produces a yellow color in the test sample. Using OT, one can only measure total chlorine—the sum of active plus spent sanitizer—making it impossible to determine whether an adequate residual exists to disinfect the water. Because of this, health departments in the United States now do not permit the use of OT at regulated facilities. See: FAS-DPD

-- pH (the H stands for hydrogen)
pH is a measure of how acidic/basic a water-based solution is. The pH scale is theoretically open-ended but most pH values are in the range from 0 to 14, with 7 being neutral. Acidic solutions have a lower pH, while basic solutions have a higher pH. pHs of less than 7 indicate acidity, whereas a pH of greater than 7 indicates basicity. At room temperature (25°C or 77°F), pure water is neither acidic nor basic and has a pH of 7. pH is really a measure of the relative amount of free hydrogen and hydroxyl ions in the water.
Also refers to base/basic (high pH) and acid/acidic (low pH)
Member CrystalRiver notes: We measure total alkalinity separately [from acidity/basicity]. It's quite possible to have a high pH (high basicity) with a low alkalinity, and vice versa.
Alkalinity is the capacity of water to resist changes in pH that would make the water more acidic. It should not be confused with basicity which is an absolute measurement on the pH scale.

-- phosphate
Phosphates are chemicals containing the element phosphorous, and they can affect water quality by causing excessive growth of algae. Water runoff from fertilizers and garden care products that are used around a pool may add phosphates to pool water. Organic matter such as leaves, twigs, algae, and other microorganisms may contribute phosphates to a pool. Many municipalities add some phosphates to the water supply to reduce levels of lead and copper.

-- plaster
A pasty composition (as of lime or gypsum, water, and sand) that hardens on drying and is used for coating walls, ceilings, and partitions. [see: plaster finishes article]

-- pool filters Maintenance and Cleaning of Pool Filters - Trouble Free Pool
There are three basic types of pool filters, all in widespread use – Sand, DE (diatomaceous earth) and Cartridge. Each type has its pros and cons, but when used properly, any of the three will do an excellent job of keeping your pool clear and free of all but the smallest particles.

-- pool heaters (gas, heat pump, solar) Pool Heaters Explained - Trouble Free Pool

-- PoolMath PoolMath - Trouble Free Pool (or PoolMath for the online version)
TFP's amazing online/app formulas designed to help newbies and pool experts find just the right amount of chemicals to add to their pools for crystal clear and healthy pool water!

-- pool types (vinyl, plaster/cement/gunite, fiberglass) Pool Surfaces - Trouble Free Pool

-- PPM (parts per million) and PPB (parts per billion)

-- reagent
A substance used in a chemical reaction to detect, measure, examine, or produce other substances. Pool water test kits use reagents to measure things such as Free Chlorine, Combined Chlorine, pH, etc.

-- shock/shocking (see: SLAM)

-- shotcrete (see: gunite)

-- SLAM (Shock Level and Maintain) (Perform the Overnight FC Loss Test (OCLT) - Trouble Free Pool)

-- sequestrant
Is any of several chemicals that bind to metal ions dissolved in the water and prevent them from depositing as stains. All sequestrants break down slowly over time, so you need to add more at regular intervals to replace the portion that has broken down. A metal sequestrant holds onto metals to prevent them from staining pool surfaces. It's only needed if you've got metals (iron, copper, manganese) in your water, such as sometimes occurs in well water

-- stabilizer (such as cyanuric acid [CYA]) Chlorine / CYA Chart - Trouble Free Pool
Added to chlorine tablets (jokingly referred to as "hockey pucks") and/or as a separate product for pool water. Member CrystalRiver notes that [stabilizer is] added to the pucks ... because chlorine is a gas that must be bound to something (stabilizer) in order to make a solid form. Generally, the more stabilizer builds up to high levels in your pool, the more chlorine you need to maintain the chlorine's effectiveness.
You'll see reference on TFP that CYA/stabilizer doesn't evaporate from pool water, thus continues to build up over time when being regularly added to a pool's water. In order to reduce stabilizer levels you'll need to remove pool water and replace with fresh (non-stabilized) water. Since the CYA doesn't evaporate per se, think of it like salt in ocean water. The water in the ocean will evaporate but the salt will only concentrate as the water dries up. Adding fresh water doesn't change the amount of salt in the water, you've got to take some salty water away and add fresh water to reduce the salt concentration. Same goes for CYA in the pool.
Although Cal-Hypo tablets are cyanuric acid-free (CYA, stabilizer), they use a special feeder because they dissolve differently than the other chlorine/stabilizer tablets.

-- stirrer (see: magnetic stirrer, or perhaps just enjoy imagining a swizzle stick in your favorite pool-side drink <G>)

-- SW (salt water)

-- SWG (Salt Water chlorine Generator)

-- TA (Total Alkalinity) ABC's of Pool Water Chemistry - Trouble Free Pool

-- TH (total hardness) ABC's of Pool Water Chemistry - Trouble Free Pool

-- titrate/titration
To ascertain the quantity of a given constituent by adding a liquid reagent [see: reagent] of known strength and measuring the volume necessary to convert the constituent to another form

-- TDS (total dissolved solids)

-- test kit
Used on this site, the term refers to a commercial "kit" that contains chemicals, containers, instructions and charts to measure pool water conditions.

-- Trouble Free Pool Care (TFPC) What is TFPC? - Trouble Free Pool
A methodology based on the belief any pool owner can achieve and maintain safe, crystal clear pool water, without high expense.

-- Tincture
A solution of alcohol or of alcohol and water, containing animal, vegetable, or chemical drugs

-- UV (ultra violet [light])

-- Water hardness/softness
The hardness of water is determined primarily by the amount of calcium and magnesium it contains. Higher levels of these and other minerals make water hard. Water softening systems work by reducing the concentrations of minerals from the water. Instead of having higher levels of calcium and magnesium, soft water tends to have higher concentrations of sodium, or salt.
Last edited:


Well-known member
Jun 19, 2020
Alkalinity is not the same as basicity (pH section).

Nitpicking here, but pH is not a scale from 0 to 14 - there are negative pHes and those over 14. Hopefully never in or near you pool, though!

CSI and LSI are not identical, though similar. They serve similar purposes, to determine the likelihood of calcium issues. One is intended to be easier to manually calculate on the job site.

Stabilizer is always (not "often") in pucks. It's not added to the pucks in order to help your water, it's there because chlorine is a gas that must be bound to something (stabilizer) in order to make a solid form.


Jun 19, 2020
SE Florida
Thanks CrystalRiver for your input!
I'll modify the pH scale info.
Pucks and stabilizer - I went with discussion here regarding CalHypo pucks without stabilizer, so hedged my definition with "often" just so I wouldn't get zinged on that one LOL However I'll copy your comment and put it in the list above ;-)
I wasn't implying that CSI/LSI are the same, rather they sometimes come up together in discussion. I'll take away the reference to each other in my list.
I don't think I used the term 'basicity' regarding pH? If so I'll fix that. When it comes to chemistry (and mixing/using chemicals in a pool) it's better to be correct than mostly correct ;)
Last edited:


Gold Supporter
Jul 9, 2019
Winnipeg, Manitoba
Actually I'd hedge my bets by saying something along the lines of 'pucks usually have CYA except for the occasional ones that use Calcium aka CalHypo". I ended up adding a lot of calcium to my pool due to a poor understanding of that point.



Well-known member
Jun 19, 2020
You're right, I was forgetting about CalHypo.

Re: basicity vs alkalinity - you said pH measures acidity vs alkalinity. It's actually acidity vs basicity. That's why we measure total alkalinity separately. It's quite possible to have a high pH (high basicity) with a low alkalinity, and vice versa. I just started working a pool with a total alkalinity of 20 and a pH off the charts high, that took three doses of acid to get to come down onto the pH scale.