Maintaining your pool with chlorine or salt hassle-free: the complete guide

To maintain a chlorine (or salt) pool without the hassle, always follow the same order: test, set the pH, adjust the free chlorine, protect the chlorine with stabilizer, then let filtration and cleaning do the rest. pH comes first: as long as it is out of range, the chlorine will not work properly and every treatment will cost more.

Water environment experts since 1998, we are giving you here the routine we recommend, with the products from the CTX range that we use and the dosages as they appear on their data sheets.

The routine in the right order

A clear pool is not a matter of random dosing, but of sequence. Each adjustment prepares the next: a correct pH makes the chlorine effective, stabilized chlorine lasts longer, and proper filtration removes what the chemistry has gathered.

Test at least twice a week during the season, preferably at the same time, with a test kit. The chlorine and pH test kit is enough to start; add the control of stabilizer and alkalinity (TAC) in the spring. Test strips and reagents expire: a box opened last year often gives erratic results.

pH first

When the pH is too high, the free chlorine becomes very weak and the pool consumes more. Our benchmark: stay between 7.0 and 7.4, and never exceed 7.6. A pH that is too low is not desirable either: we correct in both directions, in small doses.

• pH too high (above 7.6): we use a pH minus. On the data sheet of the CTX-15 pH- liquid, the indicated dosage is 3.25 L per 100 m³ to lower the pH by 0.2. The CTX-10 pH Minus granules also exists for small volumes.
• pH too low (below 6.8): we use a pH plus. The data sheet of the CTX pH plus indicates 150 g per 10 m³ to raise the pH by 0.2.
• Alkalinity (TAC) below 125 mg/L: a pH that "bounces" often comes from there. The CTX-21 Alka Plus stabilizes the pH: 180 g per 10 m³ increases the TAC by 10 mg/L, according to the data sheet.

In all cases, distribute the product evenly over the water, with the filtration running, in the absence of swimmers, and check again a few hours later.

Free chlorine: slow daily, shock when needed

Free chlorine is what actually disinfects the water. For a private pool, the common benchmark is 1 to 3 mg/L, with a pH between 7.0 and 7.4. Two families of products complement each other:

• Slow chlorine, in tablets, for weekly maintenance. The data sheet of the CTX 370 indicates 1 tablet of 250 g per 25 m³ per week, to be placed in the skimmer or a floating dispenser, never thrown directly into the pool to avoid any discoloration of the liner. The 20 g tablets (CTX 20 g tablets) are suitable for small volumes.
• Shock chlorine, fast-dissolving, to quickly raise the level after a storm, heavy use, or restarting. The CTX shock chlorine granules (55% available chlorine) is dosed, for a shock treatment, at 150 g per 10 m³ according to its data sheet. The CTX ClorShock tablets offer an effervescent action: 6 to 7 tablets per 10 m³.

If you prefer a single product, the CTX Action+ 10-in-1 combines disinfection, algae treatment, and flocculation: 1 tablet of 250 g per 25 m³ per week. Practical, but less flexible to dose than slow chlorine alone. To know the exact quantity, our article on the tablet dosage per m³ details the calculation.

Too high a level after a shock? Cut off all input, uncover the pool, and let the filtration run: the sun lowers the chlorine in a few days. To go faster, the CTX Chlorine Neutralizer is dosed at 100 g to reduce the residual chlorine of 100 m³ by approximately 0.5 mg/L, to be re-measured between additions. We detail the options in Too much chlorine in the pool.

Stabilizer

The sun degrades free chlorine. The stabilizer (cyanuric acid) protects it from UV rays and prolongs its effect. The data sheet of the CTX chlorine stabilizer indicates maintaining around 25 to 40 mg/L, by adding it to the skimmers or the pre-filter, with the filtration running. It is intended for pools treated with unstabilized liquid chlorine, hypochlorites, or a salt chlorinator; with automatic regulation, the data sheet specifies a maximum of 20 mg/L.

Be careful with accumulation: slow chlorine tablets already contain stabilizer, which accumulates season after season. Measure before adding more, and renew part of the water if the level becomes too high.

Cloudy or green water: flocculant or clarifier?

Green water comes from a proliferation of suspended algae, often linked to an imbalance: pH too high, insufficient chlorine, filtration too short. If you can still see the first 20 centimeters below the surface, the water usually catches up in a few days with shock chlorine. To check that the water is indeed green, take a glass in a transparent container.

Once the chemistry is restored, clarity remains. The flocculant forms large flakes: fast, suitable for very cloudy water, often followed by vacuuming the deposit. The clarifier forms small aggregates that the filter retains: more gradual, without water loss. The CTX data sheets give clear benchmarks:

• The CTX natural flocculant, based on chitosan: 40 ml per 50 m³ every week for maintenance, filtration running for at least six hours. In cloudy water, the data sheet recommends doubling or tripling the dose.
• The CTX Flocculant Gel, in single doses: 1 dose in the skimmer basket for a pool of 50 to 60 m³, then filter cleaning after 24 hours.
• The CTX-41 liquid flocculant: 1 L per 100 m³ in cloudy water, 0.5 L as a preventive measure.

For mustard algae, which are more stubborn, see our dedicated article.

Filtration and filtration time

Filtration is the engine of the pool: without circulation, no product distributes. A common benchmark is to filter every day for a number of hours equal to half the water temperature, i.e., about 10 hours at 20 °C. To be adjusted according to use, weather, and the appearance of the water.

• Monitor the pressure gauge. A rising pressure indicates a clogged filter or a valve not fully open; too low a pressure can come from a seized or clogged pump.
• Backwash according to the manufacturer's instructions, then rinse. Also empty the skimmer and pre-filter baskets.
• Renew the sand when it is worn out: it hardens and calcifies over time, which creates channels where the water passes without being filtered.

To choose or replace your equipment, see our guide how to choose a sand filter and the selection of filters for chlorine pools.

Cleaning: net, vacuum, robot

What chemistry does not solve, cleaning solves. In the morning, the net removes leaves and insects before they sink and feed the water with organic matter. Every week, we brush the walls and vacuum the bottom.

• The leaf blower connects to the skimmer: see how to connect it to your skimmer.
• The robot does this work alone. Cordless models, like the AquaForte M30, avoid cables; the entire selection is in our pool vacuums.
• For mud or sludge, the robot is not always enough: see the mud vacuum and how to clean sludge.

The waterline sometimes requires a dedicated cleaner, like the CTX 56 Netoline, and the limescale an appropriate treatment for your liner: see how to reduce limescale.

Winterizing and de-winterizing

In autumn, a good winterizing avoids starting from scratch in the spring. Here is the sequence described on the data sheet of the CTX 551C WinterStar Power.

1. Wait until the water drops below 15 °C, without having stopped the maintenance treatment.
2. Do a shock chlorination with a CTX shock chlorine.
3. The next day, check the pH: it must be between 7 and 7.2.
4. Pour the winterizing product with the dosing bottle, filtration running, and repeat it in mid-winter.

In the spring, the restart follows the same logic as the routine: remove the cover and winterizing accessories, restart the pump by checking the pressure gauge, analyze the water (pH, stabilizer, TAC), do a shock treatment if needed, then a backwash 24 hours later. The detail is in cleaning a pool after winter.

The weekly checklist

• Measure the pH and free chlorine, twice a week.
• Correct the pH before adding chlorine.
• Check the tablets in the skimmer or dispenser.
• Empty the skimmer and pre-filter baskets, read the pressure gauge.
• Use the net, brush, vacuum or start the robot.
• Check the stabilizer and TAC in the spring, then as needed.

Frequently asked questions

Should I set the pH before adding chlorine?

Yes. A pH that is too high reduces the efficiency of chlorine and increases its consumption. We aim for 7.0 to 7.4, we correct with pH minus or pH plus, then we adjust the chlorine.

What free chlorine level to aim for in a private pool?

The common benchmark is 1 to 3 mg/L. Some data sheets indicate a narrower range, for example 0.6 to 2 mg/L for CTX 370: always follow the label of your product.

What is chlorine stabilizer used for?

It protects chlorine from degradation by the sun's UV rays. The CTX stabilizer data sheet indicates aiming for around 25 to 40 mg/L. Slow chlorine tablets already contain it: measure before adding more.

Flocculant or clarifier for cloudy water?

The flocculant forms large flakes and acts quickly, often with a deposit vacuuming. The clarifier forms small aggregates that the filter retains gradually, without water loss.

How many hours to filter the pool?

A common benchmark is to filter every day for a number of hours equal to half the water temperature, i.e., about 10 h at 20 °C. We adjust according to use and the appearance of the water.

Is the routine the same for a salt pool?

In broad strokes, yes: the pH remains the first adjustment, and the stabilizer protects the chlorine produced by the chlorinator. Follow the recommendations of the manufacturer of your chlorinator.

When should the pool be winterized?

The CTX WinterStar Power data sheet indicates intervening at the end of the season, when the water drops below 15 °C: shock chlorination, pH between 7 and 7.2 the next day, then winterizing product.

To go further

• How to connect the leaf blower to the skimmer
• How to naturally reduce limescale in pool water
• How to empty a pool with a bottom drain
• How to clean sludge from a pool
• How to clean an above-ground pool after winter
• How to treat green water in a pool
• How to treat mustard algae in a pool
• How to maintain your polyester shell pool

Do you prefer swimming without chlorine?

If the idea of water without chemical disinfectants appeals to you, read our complete natural pool guide, or start with how to build your own natural or eco-friendly pool.