Chlorine Demand
Chlorine Demand and swimming pool water chemistry. Good weekly pool maintenance to give you the pool perfect for you.

Pool Water Balance
Your swimming pool chlorine demand (residual chlorine) might be the the single most important reading you do with your pool, yet residual chlorine is the most overlooked aspect of swimming pool care. Neglect can cause cloudy pool water.

Definition Residual chlorine is when any organic matter (animals, swimmer sweat, urine, saliva, green pool algae, brown algae, grass clippings, leaves, etc...) enters the pool and your pool chlorine oxidizes this matter and kills it. The result is called chloramines, or chloramination.The more organic matter you have in your pool the more chlorine is needed. This is not to be confused with
combined chlorine
or free available chlorine. Chlorine demand is the amount of pool chlorine (or Bromine) your swimming pool, Spa, or Hot Tub is using and knowing this will also tell you how much organic matter is in your swimming pool. Remember that neither a
pool ionizer
nor your salt water swimming pools and
salt cells
will give you a good and proper swimming pool shock. Low or high cyanuric acid (pool stabilizer) levels could contribute to a high residual chlorine demand.

High Chlorine Demand On A Pipe
How To Measure Chlorine Demand To measure your residual chlorine (and this can be done for either your swimming pool or Hot Tub) you should:- Measure your pool chlorine level with a good pool water testing kit. I recommend an
FAS-DPD K-2006 Taylor test kit
- Then perform a good
pool shock
(or Hot Tub) up to 10ppm or maybe even a little over. I prefer
Calcium Hypochlorite
but if you have high
pool pH water
or high calcium hardness, you may want to use
Sodium Hypochlorite/
liquid chlorine or bleach.
- Allow the swimming pool to sit for 24 hours. If you're doing this with a Hot Tub, you can cover it.
Don't use the swimming pool or Hot Tub during this process or use acid neutralizers. You will get a wrong reading along with very itchy skin. - After the 24 hours, re-test the chlorine once again
- Take the 2nd measurement (after the pool shock) and divide it by the 1st measurement (your initial chlorine reading)
You now have the information you need. The above will tell you how much pool chlorine (hypochlorous acid) is left in the body of water after 24 hours. You'll want to have the highest number possible, but 100% is reaching for it. This means your swimming pool is not using any chlorine, which is highly unlikely. A 0% reading is not good either because you're using up all the chlorine very quickly. If you have
asthmatic bronchitis
you'll need to keep up on the chlorine and pool shock as the rising bacteria and chloramination in the swimming pool may put you at risk and that nasty chlorine smell. If you have any kind of chlorine allergy, or are susceptible to chlorine rash or Hot Tub rash, you may either want to reduce the amount of swimming time or look into
natural swimming pools.

Understanding Chlorine Demand To get the most accurate reading of your residual chlorine it's best to measure it after you have refilled your swimming pool or Hot Tub and before you use it.Your goal is to get as close as possible to 25% residual chlorine, meaning you've only used up 25% of your pool chlorine which leaves the other 75% to do its job. If you pool shock on a refill at 10-11ppm the next day you should have 7.5ppm. That's the goal you want to hit. Obviously after you start using the swimming pool or Hot Tub the residual chlorine will rise. If after using the swimming pool and a good pool shock and your residual chlorine is a bit higher, say 50 - 75%, it means you didn't use enough pool chlorine to decontaminate the water. Simply do another shock up to 10 - 11ppm, then re-test after 24 hours. Continue to shock and test until you get as close to the 25% range as you can. Make sure you keep up on your
filter maintenance
and backwash when needed. By using this and other
swimming pool maintenance tips,
you will surely have a swimming pool you can be proud and will reduce your pool maintenance cost. Go swimming and have fun.
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Swimming Pool Chemistry From Chlorine Demand
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