Pool Testing

DPD => a test chemical for chlorine that turns pink or red.
It is available in tablets or as a liquid. It will bleach out at high chlorine levels (usually staring around 10 ppm) so it is not good for testing very high FC levels. Many men have difficulty distinguishing between the shades of red. Used alone, it reacts to free chlorine, but when used with an iodide chemical, it can measure total chlorine.

FAS-DPD => A DPD based drop count method test (titration) for FC and CC is most accurate available method.
It can test chlorine levels up to about 50 ppm with a precision as great as .2 ppm. It is a better chlorine testing method and can even be used by someone who is colorblind since the color change from pink to colorless is easy to see.

OTO => a test chemical that turns yellow, orange or brown if chlorine is present.
It is bulletproof in that it does not bleach out at high chlorine levels and that it will always change color if chlorine is present. Recommended for reliable quick daily chlorine checks, to make sure everything is OK. Reacts to TC - total chlorine, so CC levels cannot be distinguished with OTO.

K2006 => A swimming pool test kit, made by Taylor Technologies, that we often recommend. Contains an FAS-DPD chlorine test, as well as relatively accurate CYA test. See http://pool9.net/testkits/

PF => pool factor.
A 120,000 gallon pool has a PF of 1, so adding 1 lb of CYA will add 1 ppm CYA CYA. A 12,000 gallon pool has a PF of 10, so adding 1 lb of cyanuric add will result in 10 ppm CYA

PPM => parts per million, a measure of how much of a particular chemical is present.
1 pound of chlorine gas or 1 pound of CYA added to a 120,000 gallon pool (= 1,000,000 lbs of water) will result in 1 ppm of chlorine or 1 ppm of CYA

FC => free chlorine (chlorine that's 'free' to kill algae and germs)

CC => combined chlorine. Chlorine that has reacted with people 'goo'.
Chlorine + urine is especially bad about 'creating' combined chlorine. More rarely, people form simple combined chlorine (chloramines) by using anti-algae products like Yellow Out. Combined chlorines are usually easily destroyed on OUTDOOR pools by consistent chlorination PLUS sunlight. However, massive quantities of combined chlorine can result when ammonia like materials are deliberately added, via Yellow Out or Mustard Master. Even worse problems can occur in spring time, when neglected pools have grown enough 'slime' to bio-degrade stabilizer into ammonia or urea.

TC => total chlorine - TC = FC + CC

CH or CAL => calcium hardness -- important if you have a concrete pool, high CH is a problem with heaters and SWCGs

CYA => cyanuric acid (stabilizer)

PH => usually, "pH". The standard measure of how acidic or basic water is.
7.0 is roughly neutral; 5.0 is acidic; 9.0 is basic. Different bits of the human body range from 3.0 to 8.8. Pools however, need to be maintained between 7.0 and 8.0, to avoid pool damage, as well as other complications with chemistry.
[ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3195546/ ]

TA => total alkalinity, a measure of the resistance of a particular water to pH change.

TDS => total dissolved solids.
Usually this is NOT important, but used to be emphasized by pool stores, to sell chemicals.

Pool Chemicals

CH, cal hypo => calcium hypochlorite, aka "HTH" aka "shock".
A form of chlorine that adds calcium to the water, but no stabilizer. Slow dissolving white granules.

Dichlor - sodium dichloroisocyanurate dihydrate.
A form of chlorine that is about 1/2 chlorine, and 1/2 stabilizer. Fast dissolving white granules. Adds 9 ppm CYA for every 10 ppm FC.

Trichlor => trichloro-isocyanuric acid.
A form of chlorine that is usually 90% available chlorine and 45% available stabilizer. (I know those don't add up, but that's still correct. The explanation is a long gruesome chemical mess.) Usually sold as 3" tablets or 1" pellets. Very slow dissolving. Adds 6 ppm CYA for every 10 ppm FC added.

SH, LC, bleach => water solution of sodium hypochlorite. Sold as plain bleach at Walmart, etc. Sold as liquid chlorine by some pool stores. Greenish yellow liquid is instantly available -- no dissolving required!

Bicarb => Baking soda, sold expensively by pool stores as "Alkalinity Increaser".
Often available in orange Arm and Hammer bags for as little as $0.50/lb. Pool stores sell less pure versions for $1.50 - $2.50/lb, and call it "sodium hydrogen carbonate" or "sodium acid carbonate" to mislead buyers.

Borax => white granules that raise the pH and add borates.
Sold by Walmart, etc as "20 Mule Team Borax". Sold very expensively by pool stores as "Optimizer" or "Supreme". Do NOT confuse borax with Boraxo detergent!

CYA => cyanuric acid or stabilizer.
Prevents solar UV from destroying pool chlorine almost instantly. Usually sold as white or tan flakes. May be cheaper and is easier as dichlor.

HEDP => a metal sequestrant that is sometimes needed if there are metals in the water.

MSDS => material safety data sheet is an information sheet that must, by law, list all hazardous ingredients in a product.
Only the hazardous ingredients need be listed and terms such as "proprietary mixture" or a general description of the other ingredients is permitted.

UV => ultraviolet light, from the sun or a set of UV lamps.
UV can be useful in indoor pools to help combat persistent combined chlorine. It's pretty much useless in outdoor pools that are exposed to sunlight.


BBB => Bleach, Borax, Baking soda. Often as "BBB Method".
I posted some pages on PoolSolutions, almost 20 years ago, explaining how some pool chemicals could be purchased more cheaply from Walmart, etc. A long time moderator, CarlD, began to refer to the over-all methods taught here as the "BBB Method", and the name caught on. But the idea that bleach, borax or baking soda were ESSENTIAL to the "BBB Method" has ALWAYS been mistaken.

People goo => Pee, poop, sweat, snot, spit.
When people swim, they add 'people goo' to the pool, which reacts with chlorine to form 'combined chlorine'. Urine is especially bad about this.

POP => Pool Owner Patience, the lack of which often makes pool owners victims of pool store sales tactics.

AGP => above-ground pool

DE => diatomaceous earth powder.
DE is literally made of algae fossils, and consists of microscopic snowflake-like particles of silica. It's used as filter media instead of sand in DE filters. It is VERY important to distinguish the filter grade material from the food grade material, which is too fine for filters. Both are available on Amazon.

IGP => in-ground pool

SWCG => Salt Water Chlorine Generator (Salt systems MANUFACTURE chlorine by passing electricity through salty water, during "chloride" into "chlorine".)