Chlorine Demand - watch a
video on "Pool Shocking"
Demand is a pool water chemistry topic that is getting more attention due to
changing climates, consumer's water chemistry and understanding of the
problem. It is also becoming a greater issue in many private &
Demand is defined as "the quantity of chlorine reduced or converted to
inert or less active forms of chlorine by substances in the water." Faust
and Aly's Chemistry of Water Treatment further state that, "since
chlorine is a non-selective oxidant, almost any substance in the water...will
react and consume chlorine."
In other words, the more "stuff"
dissolved in the pool water, whether organic or inorganic; chemical, vegetable
or mineral; heavy, constant rainfall can cause a chlorine demand. Or more simply
stated, not being able to successfully maintain a chlorine residual following a
shock treatment. Certain household
cleaners that are not specifically formulated for in-pool-water use will add
components such as phosphates or nitrates will interfere with the pool's
sanitizer causing a chlorine demand.
A couple of the most common causes for chlorine
demand that we see are in the spring at pool opening time. Pools are left
idle & unattended for months at end without treatment. The problem is
worsened if the pool had been closed the prior season without being thoroughly
cleaned - accumulations of leaves, debris, dirt, etc. are left to sit in the
pool for the winter. Leaves & debris will break down & add nitrogen along with
other organic contaminants leading to a chlorine demand issue. I can
personally attest that a clean & properly closed pool will open in the spring
almost worry free.
cause that may prove suspect, at least in our line of thinking, is the
Chloramine issue. As you
remember, chloramines are chlorine molecules that are chemically linked up (we
call them contaminated) with organic waste such as nitrogen, ammonia, etc.
More & more local water treatment authorities are using chloramines to
drinking water supply these days. Chloramines are pretty effective in
killing pathogens in the drinking water supply. However, chloramines are
not effective oxidizers. You've probably noticed a regular pink line in your
home sink, shower or toilet bowl, especially over the past 4 to 5 years.
Those spots need more regular cleaning. That's the same pink slime that is
in your swimming pool! Chloramines are used because they are pretty
effective and less "offensive" to those who want to rid our planet of chlorine.
That premise is utter foolishness since you can't ban or get rid of an element!
Anyway, as you top off your pool with the garden hose, you're putting more
chloramines into your pool every time and aggravating an already serious
problem. Please keep in mind that this issue is NOT pertinent to folks
with well water (you have your own issues).
Click here for further information on
BioGuard's Technical Services Department has gathered a huge amount of data
concerning chlorine demand. It appears that the situation has become more
widespread each year. Here are some actions that can help in dealing with
Doing a proper Chlorine Demand
Test. Your local BioGuard®
Insignia Dealer should have a Chlorine Demand test station. When
determining the ACTUAL Chlorine Demand, it is imperative that the solution
& corrective action be accurate. Liken it to jumping across the
Grand Canyon, if you miss, you miss! If it takes 20 lbs of Shock to
break the chlorine demand, using 19 lbs will make the problem worse; 20 lbs
or more of Shock will treat the issue.
Maintenance of an adequate
sanitizer being added to the swimming pool on a daily basis. Be sure to have
the correct number of chlorine sticks or tablets dissolving into the
pool. Check this as often as daily by visually examining the chlorine
to see that it is eroding (whether in the skimmer or in a chlorinator) at a
"normal" rate. Normal refers to what you have
"normally" experienced in the past. Cool water, slower
erosion/dissolution rate; warmer water, faster erosion/dissolution rate.
The Pool MUST BE SHOCKED EVERY
WEEK. PERIOD. Shocking oxidizes much of the "stuff" that
was mentioned earlier. Download a
FREE brochure to learn about shocking.
If you are using a solar
blanket, REMOVE IT! After ANY
chemical addition, the chemical reaction must have time to GAS-OFF in order
to achieve the proper results.
Although a singular cause for
Chlorine Demand has not been determined (there are many), we have found a common
thread in many of these cases. One common thread is if a pool is kept
closed longer in the spring (covered without a sanitizer). Heavy rainfall
that has ammonia present will cause a Chlorine Demand. Accidental addition
of household fertilizers or any compound that can be oxidized by chlorine will
result in a Chlorine Demand.
In conclusion, Chlorine Demand needs
our attention. Only careful monitoring and quick treatment may be
successful for a clear pool. PLEASE VISIT YOUR LOCAL BIOGUARD PLATINUM
DEALER REGULARLY (4 times per season).
Par Pool & Spa can perform a
Chlorine Demand test for you.
If you don't have a local
BioGuard Dealer with a Chlorine Demand Test Station, you may OVERNIGHT a
sample to us for testing & analysis. We will perform a complete BioGuard
Test using AccuScan and the AccuDemand 30 test stations and will provide you
with BioGuard Alex results as well as some of our own recommendations.
fill out this form (new window will open), print it, and include it with your ONE QUART water
sample (must be sent in a clean, plastic bottle that was NOT used to hold
cleaning fluids, soda, food in general - an empty water bottle is best). Please
note that there is a $15.00 charge for this testing & analysis service. A
portion of the fee ($10.00) may be applied to future chemical sales. We will
contact you by telephone with the results & recommendations.
Download & Print a
FREE brochure on Chlorine Demand.
More information & an expansion of this information may be found here (your
browser will open a new window).
Don't Forget the FREE Computerized Testing & Analysis!
All information contained in this
article is courtesy of the BioGuard Chem PLUS 2003, 2004 & Chem College 2007,
H2Know 2015 Reference Guide.
If you still need help, here's how to
store hours): Shelton 203-377-0100