Short answer: A pool chlorine dosing pump is a dosing pump that feeds liquid chlorine (sodium hypochlorite) solution into the pool’s circulation line continuously and in metered amounts. Because chlorine and pH are controlled together in pools, two pumps are usually used: one doses chlorine based on ORP or free chlorine measurement, the other doses pH corrector based on pH measurement. Suitable AnTech options are the Lara PR for small and medium pools, and the Nova DMPR and the Nova DMİA with free chlorine measurement for hotel and large pools.
On this page you will find why dosing pumps are used in pools, the relationship between chlorine and pH, model selection by pool type, where to install the pump and electrodes, and what to watch for in maintenance. All measurement-controlled models are listed in the pH/ORP controlled dosing pumps and dosing pumps with chlorine measurement categories.
Why Use a Chlorine Dosing Pump in a Pool?
A dosing pump keeps the chlorine level in pool water continuous and stable instead of relying on manual additions. When chlorine is added by hand at intervals, the level first rises and then falls as it is consumed; the pool is over-chlorinated for part of the day and under-chlorinated for another. A pump, by contrast, feeds the chlorine solution continuously in small doses.
- Adapts to changing consumption: Chlorine consumption in a pool changes during the day with the number of bathers, sunlight and water temperature. A measurement-controlled pump increases the dose when demand rises and reduces it when demand falls.
- Less contact with chemicals: Staff do not carry chemicals from drums to the pool; the solution travels in a closed line from the tank to the circulation line.
- Traceability: The Nova DMPR and Nova DMİA can send the measured value to a panel or recording system through a 4–20 mA output.
- Tank monitoring: A suction assembly with a level sensor alerts the pump when the chemical tank is empty, so dosing does not stop unnoticed.
Dosing pumps are for liquid chemicals. Tablet or granular chlorine products cannot be fed with a pump; pump-based systems generally use sodium hypochlorite solution.
How Are Chlorine and pH Controlled Together?
In a pool, chlorine and pH are measured separately and corrected with separate pumps, but the two are linked: as pH rises, the disinfecting power of chlorine decreases. For chlorine control to work properly, pH must therefore be kept stable first.
The relationship between ORP and pH
Chlorine added to water exists in two forms: hypochlorous acid (HOCl) and hypochlorite ion (OCl⁻). Hypochlorous acid is what actually disinfects, and its proportion falls as pH rises. ORP (redox potential) shows the oxidising power of the water in mV. ORP rises as free chlorine increases; when pH rises, however, ORP falls at the same chlorine level.
The practical consequence is this: a pump dosing chlorine by ORP will dose more chlorine when pH rises, because ORP falls. If pH is not under control, the pool can be over-chlorinated. Stabilised chlorine products containing cyanuric acid can also lower the ORP reading. That is why, in pools where chlorine is dosed by ORP, pH is kept stable with a separate pump.
Two pumps in practice
The Lara PR and Nova DMPR measure pH or ORP with a standard combination electrode; one pump controls only one of them at a time. The typical arrangement in a pool is:
- Chlorine pump: Lara PR or Nova DMPR with an ORP electrode; if chlorine has to be measured directly in ppm, the Nova DMİA with a free chlorine sensor.
- pH pump: Lara PR or Nova DMPR with a pH electrode; in pools it mostly doses pH reducer. For details, see our pH dosing pump page.
During commissioning, first bring pH to its target value, then set up chlorine. Determine the ORP target by comparing it with the free chlorine and pH values you measure at the same time with a test kit. For target chlorine and pH values, refer to the regulations that apply to your pool.
Model Selection by Pool Type
Model selection depends on the size of the pool, how heavily it is used and how much automatic control is wanted. The table below summarises three control approaches by pool type: analogue (manual adjustment), pH/ORP measurement and free chlorine measurement.
| Pool type | Chlorine dosing | pH dosing | Control approach |
|---|---|---|---|
| Small private pool, budget first | Lara A 2 L/h 10 Bar or the level-controlled Lara APS 2 L/h | Monitoring with a test kit; Lara PR 2 L/h (pH) if needed | Analogue: adjustment is manual, values are measured regularly |
| Small and medium private pool, villa | Lara PR 2 L/h 10 Bar (ORP) | Lara PR 2 L/h (pH) | pH/ORP measurement, compact, 230 V AC |
| Hotel and residential complex pool | Lara PR 10 L/h 5 Bar or Nova DMPR 10 L/h 10 Bar (ORP) | Lara PR 5 L/h 7 Bar or Nova DMPR 10 L/h (pH) | pH/ORP measurement; Nova DMPR with 4–20 mA output if monitoring is required |
| Large and public pool | Nova DMİA 10 L/h 10 Bar or Nova DMİA 25 L/h 5 Bar (free chlorine) | Nova DMPR 25 L/h 5 Bar or Nova DMPR 10 L/h (pH) | Free chlorine measured directly in ppm; measurements can be logged |
The capacities in the table are starting suggestions. The right capacity depends on the circulation flow rate, the concentration of the solution you use and the pool’s chlorine demand on its busiest day. You can calculate the required pump flow rate with our chlorine dosing calculator, entering the circulation flow rate as the water flow rate.
- Lara PR: 230 V AC, 17 W, 2–10 L/h. Offers fully digital automatic calibration with buffer solutions and a 0–60 minute measurement delay at start-up.
- Nova DMPR: 95–260 V AC, 3.5–25 L/h. Has a 4–20 mA measurement output, flow and PT100 inputs, an alarm output and a ModBus RTU communication input.
- Nova DMİA: Measures free chlorine with an amperometric sensor. The sensor and sensor housing are selected separately; the free chlorine sensors in the catalogue cost more than the pump.
How to choose capacity for a measurement-controlled pump
A pump that works by measurement doses less when chlorine demand is low and more when it rises. Capacity is therefore chosen not for an average day but for the pool’s busiest day. For example, if the circulation flow rate is 25 m³/h, the peak chlorine demand is 2 mg/L (example value) and the solution contains 10 g of active chlorine per litre, the required flow rate is 25 × 2 ÷ 10 = 5 L/h. In this case the Lara PR 5 L/h runs at full capacity with no reserve; the Lara PR 10 L/h meets the same demand at a setting of about 50%.
The AnTech catalogue also includes ready-made pH and ORP pool control systems in which the pump, measurement and electrode housing are combined on a single panel. Write to us about these systems.
Where Is a Pool Chlorine Dosing Pump Installed?
Chlorine and pH are injected into the pool circulation line after the filter, in the line where water returns to the pool. The electrodes measure sample water taken before the injection points.
Injection point
- After the filter: The chemical mixes into filtered water; concentrated solution does not reach the filter or the circulation pump.
- After the heater, if there is one: In pools with a heater or heat exchanger, injection is usually made downstream of this equipment as well.
- Separate points: Chlorine and pH corrector are not fed at the same point; leave a distance between the injection points. If acid and sodium hypochlorite meet in concentrated form, chlorine gas can be released.
- Pressure: The line pressure at the injection point must not exceed the pump’s maximum back pressure.
Electrode housing and sample line
The sample is taken at a point upstream of the chemical injection points, so the electrode measures pool water rather than chemical the pump has just injected. Water in the sample line must flow continuously and be free of air bubbles. The electrode holder type is chosen according to the installation site:
- Electrode housing with filter: Retains particles in the sample water; suitable for samples taken from the circulation line.
- Fixing fitting: Used to mount the electrode directly on the pipe.
- Immersion probe holder: Used in open tanks such as balance tanks.
- Hose-type probe holder: Connects to a sample line supplied by hose.
Each of these holders is listed as an electrode set with holder, together with the electrode and calibration solution. The sets appear on the AnTech Lara series page and can also be used with the Nova DMPR.
Interlocking with circulation, and chemical tanks
The dosing pump should run only while the circulation pump is running; otherwise chemical builds up in the stationary line. To achieve this, the pump’s power supply is switched together with circulation, or the flow sensor input on the Nova DMPR and Nova DMİA is used. Chlorine and acid tanks should be kept separate, in a ventilated place out of direct sunlight, and the pumps should be mounted upright close to the tanks. Nova pumps can also be placed on a flat surface using the mounting foot included in the package. If you would like us to carry out the installation, you can request our dosing pump installation service.
Maintaining a Pool Dosing System
Maintaining a pool dosing system covers not only the pump but also cleaning and calibrating the electrodes. If the measurement is wrong, the pool receives the wrong amount of chemical even if the pump works correctly.
- Electrode calibration: The pH electrode is calibrated with buffer solutions and the ORP electrode with calibration solution; the catalogue lists pH 4, pH 7 and 475 mV ORP calibration solutions. The Lara PR performs calibration fully digitally; on the Nova DMPR, calibration is done from the pump menu.
- Comparison with a test kit: Regularly compare the values shown by the pump with those you measure with a test kit. If the difference grows, clean the electrode and recalibrate it.
- Do not let electrodes dry out: The tips of pH and ORP electrodes must not be left dry. At the end of the season, remove the electrode and store it under the conditions recommended by the manufacturer.
- Check valves and hoses: As sodium hypochlorite dries it leaves salt crystals, which build up in the check valves and reduce dosing. Check the foot filter, hoses and check valves regularly.
- End of season: For a pump that will be idle for a long time, put the suction into clean water and flush the line; prevent chemical from drying in the pump head.
For step-by-step maintenance, see our chlorine dosing pump maintenance guide. If you would like to leave electrode calibration and periodic checks to us, write to us. The maintenance logic is the same for every chlorine dosing pump used in pool and tank applications; the difference lies in maintaining the measuring elements.
Sources
- AnTech 2025 Product Catalogue (KT_25 R02): feature lists for the Lara PR, Nova DMPR and Nova DMİA, electrode sets with holders, sensors and pool control systems.
Frequently Asked Questions
Which chlorine dosing pump is suitable for a pool?
Suitable options are the Lara PR with ORP measurement for small and medium pools, the Lara PR 10 L/h or Nova DMPR for hotel pools, and the Nova DMİA with free chlorine measurement for large and public pools. The exact capacity is calculated from the circulation flow rate and the solution concentration.
Is one pump enough for chlorine and pH?
No. The Lara PR and Nova DMPR measure only one of pH or ORP at a time and dose a single chemical. Chlorine and pH control require two separate pumps and two separate chemical tanks.
ORP or free chlorine measurement?
ORP indicates the effectiveness of chlorine indirectly and is affected by pH; when pH is kept stable, it is a common and economical method in pools. Free chlorine measurement gives the amount of chlorine directly in mg/L, but the sensor costs more.
Does the electrode or sensor come with the pump?
No. pH (P) and ORP (R) electrode sets with holders for the Lara PR and Nova DMPR, and a free chlorine sensor and sensor housing for the Nova DMİA, are selected separately.
Can a dosing pump be used in a pool that uses chlorine tablets?
Dosing pumps handle liquid chemicals; tablet and granular products cannot be fed with a pump. To switch to a pump-based system, liquid chlorine (sodium hypochlorite) solution is used.
Should the pump run at night as well?
The pump can run as long as the circulation pump is running. When circulation stops, dosing must stop too; to achieve this, switch the power supply together with circulation or use the flow input.
Where is a pool dosing pump connected?
Injection is made into the return line to the pool, after the filter (and after the heater, if there is one). Separate injection points are used for chlorine and pH; the electrode sample is taken upstream of the injection points.