Chemical Sanitizers


Pool balancing is the same, irrespective of what sanitizing solution you choose. It is important to point out, though, that your choice of sanitizers can affect pool balance to varying degrees.

We list below the characteristics of the main chlorine options for your consideration :

Granular Chlorine

A Powder
Not stabilized with cyanuric acid (chlorine stabilizer)
Has an inherent high pH (over 11)
Ideal for shock-dosing
Not 100% soluble (needs to be pre-dissolved for at least a couple of hours)
Can cause cloudiness when added if pH is too high
Typical strength for poolgard HTC chlorine is 77% available chlorine
Long shelf life

Liquid Chlorine

A Liquid
Not stabilized
Has an inherent high pH (over 13)
Ideal for shock-dosing
100% soluble (can add directly to pool)
Can be added at any pH level without causing cloudiness
Typical strength for poolgard HTC chlorine is 15% available chlorine
Short shelf life (1-2 months)

Dichlor

A powder
Stabilized with cyanuric acid (chlorine stabilizer). Therefore, better for strong sunlight conditions which can break down chlorine rapidly.
Has an inherent neutral pH (around 7.0)
Ideal for daily sanitation, as it releases chlorine slowly
100% soluble (no need to be pre-dissolve)
Won’t cause cloudiness when added if pH is too high
Typical strength for poolgard Dichlor is 56% available chlorine
Long shelf life

Tri-tabs

A 3 inch slow release tablet
Stabilized with cyanuric acid (chlorine stabilizer). Therefore, better for strong sunlight conditions which can break down chlorine rapidly.
Has an inherent acidic pH (around 3.0)
Ideal for daily sanitation, as it releases chlorine slowly lasting up to a week
100% soluble (no need to be pre-dissolve)
Won’t cause cloudiness when added if pH is too high
Typical strength for poolgard Tri-tabs is 90% available chlorine
Long shelf life
Can cause bleaching because of its concentration if allowed to come into close or direct contact with the pool surface

Cyanuric acid (known as “chlorine stabilizer”) is a natural part of Dichlor and Tri-tabs. It’s presence helps slow down the breakdown of chlorine in strong sunlight, extending it’s useful life.

However, cyanuric acid once in the pool does not break down. It’s level keeps rising. The level of cyanuric acid in the pool must be monitored and checked as excessively high levels can cause chlorine to become ineffective as a sanitizer causing water quality problems. The only way to reduce cyanuric acids level is through water dilution. This typically happens as a result of backwashing, vacuuming to waste, water dilution with rain etc.

Indoor pools do not require cyanuric acid.

If your pool is outdoors and you use liquid chlorine, granular chlorine or a salt chlorinator as your daily sanitizer, you will need to add cyanuric acid to the pool.

Your choice of sanitizers should take account of the effect of cyanuric acid levels in your pool.

Select a daily sanitizer and a shock-dosing sanitizer

A daily sanitizer is used to keep your pool sanitized on a daily basis – that is, a residual level of chlorine is maintained in the pool between 1-3 ppm to keep the pool water healthy.

Tri-tabs are most common, as they can last up to a week, reducing the chore of adding chlorine to the pool. However, because of it’s strong bleaching capability Dichlor is often used for vinyl-liner pools. Dichlor is less harsh on pool surfaces, but needs to be broadcast over the pool surface (or first diluted in a bucket) and added to the pool every 1 to 3 days to maintain the desired chlorine residual.

As indoor pools do not require cyanuric acid, liquid chlorine or granular chlorine are often used as the daily sanitizer.

A shock-dose sanitizer is then needed. A shock-dose is an extra large dose of chlorine added to the pool water to:

  • kill any algae, bacteria, viruses resistant to the normal chlorine level
  • to burn out the build-up of organic contaminants (chlorines oxidation effect acts as a clarifier)
  • to super-chlorinate pool water ; this is the process of adding chlorine to the pool to burn out chloramines (the build-up of chlorine by-products in the water that are responsible for a strong chlorine smell and itchy eyes)

Granular chlorine and liquid chlorine are ideal as shock-dose sanitizers as they release chlorine fast for a powerful effect. Because they are unstabilized, they do not increase the build up of cyanuric acid in the pool.

Start-up and sanitizer dosing

(All dosages based on 45,000L pool. Adjust your dosage to suit)

Poolgard HTC Granular Chlorine

  • For freshly filled pools check pH is between 7.0–7.4 range and then shock-dose pool with 1 kg pre-dissolved HTC Granular Chlorine per 45,000L and filter for 24 hours.  Then add 1.5 kg Chlorine Stabilizer (either directly to pool or through a “sock” in skimmer basket).  This will dissolve slowly over 2-3 days.
  •  Once initial shock-dose added, start daily dose of HTC Granular Chlorine pre-dissolved at 300g per 45,000L.  Check pH weekly.
  •  Under heavy bathing loads or extremely hot weather increase daily dose by 25%.
  • Continue to filter pool one hour per 4500L daily (45,000L = 10 hours).  As algae can adapt to uniform chlorine levels it is essential that shock-dosing with HTC Granular Chlorine is carried out at 1kg per 45,000L fortnightly during the summer season.  Shock-dose in the early evening to maximize effectiveness.
  • NOTE  Always pre-dissolve HTC Granular Chlorine in a bucket at the rate of no more than 500g per 10L. Leave to stand for at least 2 hours to dissolve. In the evening, add only the clear liquid to the pool, leaving the insoluble residue in the bucket. Discard the residue.
  • To winterise the pool shock-dose with 1kg HTC Granular Chlorine per 45,000L and then add 600ml Wintergard 50 at least 24 hours later.  Repeat process every month.

Poolgard 100% Soluble Dichlor Powder

  • For freshly filled pools follow same initial programme for HTC Granular Chlorine except reduce Chlorine Stabilizer amount to 1kg per 45,000L.  Then add 100g Dichlor per 45,000L direct to pool on a daily basis.  Shock-dose every 2 weeks with 1kg HTC Granular Chlorine per 45,000L.  Check pH weekly.
  • To winterise the pool shock-dose with 1kg HTC Granular Chlorine per 45,000L and then add 600ml Wintergard 50 at least 24 hours later.  Repeat process every month.

Poolgard Tri-Tabs

  • For freshly filled pools follow same start up as for Dichlor. Place tablets in an in-line feeder and adjust dial to maintain a free available chlorine level of 1.0-2.0 ppm. Alternatively, place a tablet in skimmer and replace every 3–4 days.  Check pH weekly.  Shock-dose with HTC Granular Chlorine every week during the summer season.
  • NOTE  Never add HTC granular chlorine directly to skimmer whether pre-dissolved or not as these chemicals are incompatible in the dry state.  A dangerous chemical reaction could occur.
  • To winterise the pool shock-dose with 1kg HTC Granular Chlorine per 45,000L and then add 600ml Wintergard 50 at least 24 hours later.  Repeat process every month.

Poolgard 15% Liquid Chlorine

  • For freshly filled pools shock-dose with 3.5L Liquid Chlorine per 45,000L and filter 24 hours.  Then add 1.5 kg Chlorine Stabilizer (either direct to pool or through bag placed in skimmer).
  • Then add 600ml Liquid Chlorine per 45,000L daily.  Check pH weekly.
  • During summer shock-dose pool fortnightly with 3.5L Liquid Chlorine per 45,000L.
  • To winterise shock-dose monthly with 5L Liquid Chlorine.