Short answer: A pH dosing pump is a dosing pump that measures the pH of water with an electrode and automatically doses a pH reducer or pH increaser to reach the target value. AnTech has two series for this job: the compact Lara PR (2–10 L/h), which runs on 230 V AC, and the Nova DMPR (3.5–25 L/h), with a 95–260 V AC supply and a 4–20 mA measurement output. In both series the pH electrode and its holder are selected separately from the pump, as a set.
pH-controlled dosing pumps are used in swimming pools, water storage tanks and industrial process lines. On this page you will find why pH is corrected, which chemicals are used, which model among the pH/ORP controlled dosing pumps suits you, and how automatic pH control is set up step by step.
What Is a pH Dosing Pump?
A pH dosing pump is a dosing pump that combines measurement, control and dosing in a single unit and adjusts the dose according to the measured pH of the water. A constant-rate pump takes the amount of chemical to deliver from its setting; a pH dosing pump takes it from the electrode measurement.
An automatic pH dosing system consists of the following parts:
- pH electrode: A combination electrode that measures the pH of the water.
- Electrode holder: The housing, fitting or probe holder that places the electrode in a sample line, pipe or tank.
- Pump: A digital electromagnetic dosing pump with a measurement input (Lara PR or Nova DMPR).
- Chemical tank and suction assembly: The pH reducer or increaser solution and a suction assembly with a level sensor.
- Discharge line and injection point: The discharge assembly that delivers the chemical into the line where the water flows.
The Nova DMPR increases the dose as the measured value moves away from the target and reduces it as the value approaches the target. The same pumps can also work with an ORP electrode instead of pH, in which case they control chlorine dosing; however, a pump uses only one measurement (pH or ORP) at a time.
Why Is pH Corrected?
pH is corrected because the disinfecting power of chlorine, corrosion in pipes and scaling all depend directly on the pH of the water.
Chlorine effectiveness depends on pH
Chlorine added to water exists in two forms: hypochlorous acid (HOCl) and hypochlorite ion (OCl⁻). The stronger form, hypochlorous acid, is what actually disinfects. As pH rises, the proportion of hypochlorous acid falls; at around pH 7.5 roughly half of the chlorine is in this form, and this balance also shifts slightly with temperature. In other words, the same amount of chlorine has a weaker effect in water with a high pH. In any chlorinated system, however accurately a chlorine dosing pump works, the result will not be as intended if pH is not under control.
Corrosion and scaling
Soft water with a low pH can accelerate corrosion in metal pipes, fittings and heat exchangers. In hard water with a high pH, calcium carbonate precipitates; scale builds up in pipes, heaters and filters, and the water may turn cloudy. The appropriate pH range depends on the hardness and alkalinity of the water.
Process and discharge requirements
In industrial processes, the efficiency of chemical reactions, product quality and equipment life can depend on pH. Limit values for pH also apply to wastewater discharge. For these values, refer to the regulations and permits that apply to your facility.
pH Reducer and Increaser Chemicals
Acidic chemicals are used to lower pH and alkaline chemicals to raise it; the wetted parts of the pump must be compatible with the chemical. The table below gives a general summary of commonly used chemicals:
| Chemical | Effect | Point to note |
|---|---|---|
| Sulphuric acid (diluted, commercial pH reducer) | Lowers pH | The concentrated form is very dangerous; a diluted commercial product is preferred. |
| Hydrochloric acid (muriatic acid) | Lowers pH | Its fumes can corrode nearby metal parts; the tank must be closed and the area ventilated. |
| Sodium bisulphate (dry acid) | Lowers pH | A powder; it is fully dissolved in water and dosed as a solution. |
| Sodium hydroxide (caustic soda) | Raises pH | A strong base; hazardous to skin and eyes, and O-ring compatibility must be checked separately. |
| Sodium carbonate (soda ash) | Raises pH | Also increases alkalinity; if not fully dissolved, it can leave deposits in the check valves. |
Material compatibility
In the standard construction of the Lara PR and Nova DMPR, the pump head is PVDF, the diaphragm PTFE, the balls zirconia and the O-rings Viton. The suction and discharge assemblies are PP on the Lara PR and PVDF on the Nova DMPR. Catalogue prices are for the standard models with Viton O-rings; EPDM and Teflon O-ring options are also listed for the Nova and Lara series. Particularly with alkaline chemicals and concentrated acids, send us the name and concentration of the chemical you will use and we will check material compatibility together.
Safety
- Acid and sodium hypochlorite must never meet in the same tank, the same suction assembly or the same injection point; this mixture releases chlorine gas.
- When diluting, add acid to water; never pour water onto acid.
- Label the tanks; use gloves, goggles and suitable protective equipment.
AnTech Models with pH Control
AnTech’s pH-controlled dosing pumps are the Lara PR (4 models) and Nova DMPR (3 models) series; both dose according to pH or ORP measurement. Prices exclude VAT and are updated with the daily exchange rate; you can compare all models on our chlorine dosing pump prices page.
| Model | Max. flow | Max. pressure | Supply, power | Price (excl. VAT) |
|---|---|---|---|---|
| Lara PR 2 L/h 10 Bar | 2 L/h | 10 bar | 230 V AC, 17 W | $728.41 |
| Lara PR 5 L/h 7 Bar | 5 L/h | 7 bar | 230 V AC, 17 W | $728.41 |
| Lara PR 10 L/h 5 Bar | 10 L/h | 5 bar | 230 V AC, 17 W | $803.26 |
| Lara PR 2 L/h 20 Bar | 2 L/h | 20 bar | 230 V AC, 17 W | $836.78 |
| Nova DMPR 3.5 L/h 20 Bar | 3.5 L/h | 20 bar | 95–260 V AC, 15 W | $986.48 |
| Nova DMPR 10 L/h 10 Bar | 10 L/h | 10 bar | 95–260 V AC, 25 W | $936.21 |
| Nova DMPR 25 L/h 5 Bar | 25 L/h | 5 bar | 95–260 V AC, 27 W | $1,052.39 |
Lara PR or Nova DMPR?
The Lara PR is the more compact and more affordable option; the Nova DMPR offers higher flow, a wide supply voltage range and a monitoring output.
- Lara PR: pH or ORP measurement with a standard combination electrode, fully digital automatic calibration with buffer solutions, a 0–60 minute measurement delay at start-up, volumetric proportional dosing with a water meter, 4–20 mA analogue input, liquid level control and alarm relay, timer and user password. Details are on the AnTech Lara series page.
- Nova DMPR: Proportional dosing based on pH or ORP measurement, sensor calibration from the menu, a 4–20 mA output that transmits the measured value, all Nova D operating modes, chemical and water level, flow and PT100 inputs, an alarm output and a ModBus RTU (RS485) communication input. Details are on the AnTech Nova series page.
If you need to send the measured pH value to an automation system or data logger, choose the Nova DMPR. If pH control with a compact pump is enough for a pool, tank or small process line, the Lara PR will usually do the job.
Electrode sets are sold separately
pH measurement requires an electrode set with holder; it does not come with the pump. The catalogue lists eight P-coded sets for pH: the numbers P 1–P 4 indicate the holder type, and the letters S and E indicate the electrode body (S: Sensor XS with Ultem body, E: electrode with polycarbonate body). Each set contains an electrode, a holder and pH calibration solution.
| Set | Holder | Suitable installation |
|---|---|---|
| P 1 | Immersion probe holder | Open tank, balance tank |
| P 2 | Electrode housing with filter and mounting kit | Sample water taken from the line |
| P 3 | 1/2″–12 mm PP fixing fitting | Directly on the pipe |
| P 4 | Hose-type probe holder | Sample line supplied by hose |
The catalogue states that the electrode sets with holders listed for the Lara PR can also be used with the Nova DMPR. If you are not sure which set is suitable, send us a photo of your installation site.
How to Set Up Automatic pH Control
Automatic pH control is set up by placing the electrode in the right location, calibrating with buffer solutions, entering the target value and connecting the pump to the chemical line.
- Electrode location: Place the electrode in a sample line or housing where water flows continuously and there are no air bubbles. The sample must be taken upstream of the chemical injection point; if the electrode measures water into which chemical has just been mixed, the pump will react incorrectly. In tank applications, use an immersion holder and make sure the tank is mixed.
- Electrode mounting: Fit the electrode with its tip pointing downwards; avoid inverted or horizontal positions. The electrode tip must not be left dry; remove the protective cap just before mounting.
- Cable: Connect the electrode cable to the pump’s measurement input and route it away from power cables.
- Calibration: Calibrate the electrode with buffer solutions; the catalogue lists pH 7 and pH 4 calibration solutions. The Lara PR performs calibration fully digitally; on the Nova DMPR, calibration is done from the pump menu. Do not pour used buffer solution back into its bottle.
- Start-up delay: On the Lara PR, a measurement settling time of 0–60 minutes can be entered for start-up. During this time the pump does not dose by measurement, preventing overdosing based on a false reading before the electrode has stabilised.
- Target and dose setting: During commissioning, correctly define the target pH value and the direction of the chemical you use (reducer or increaser). In the first days, start with a low capacity limit and watch how the system responds.
- Safety inputs: Connect the suction assembly with a level sensor to get a warning when the tank runs empty. To prevent dosing when water is not flowing, run the pump together with the circulation or feed pump; on the Nova DMPR you can use the flow sensor input.
- First days: Compare the value shown by the pump with a handheld meter or test kit; if there is a difference, repeat the calibration.
Unlike chlorine dosing, pH dosing cannot be calculated with a single formula; the amount of chemical needed depends on the alkalinity of the water. You can gauge the requirement in advance by adding chemical gradually to a small sample and measuring the change in pH. If you would like to leave electrode calibration to us, you can request our pH and chlorine sensor calibration service.
Pool, Tank and Process Applications
pH dosing pumps are used mostly in swimming pools, water storage tanks, and industrial process and wastewater lines.
Swimming pools
In a pool, pH control is a prerequisite for chlorine control. Because sodium hypochlorite is an alkaline solution, pH in chlorinated pools often tends to rise; that is why the pH pump in pools usually doses pH reducer. In the typical arrangement, one pump works with pH measurement and the other with ORP or free chlorine measurement. For pool layout and model selection, see our pool chlorine dosing pump page.
Water storage tanks and well water
In tanks, pH correction is carried out both to increase the effectiveness of chlorine and to protect pipes and plumbing equipment. In open tanks a set with an immersion holder can be used, and on the tank inlet or outlet line a set with a housing or fitting. On lines with varying flow, the Lara PR can also perform volumetric proportional dosing when connected to a water meter.
Process and wastewater
In industrial processes and wastewater neutralisation, chemical demand can be higher. On such lines, the Nova DMPR, which delivers up to 25 L/h, can be connected to plant automation through its 4–20 mA measurement output and ModBus RTU communication input. In closed circuits with high pressure, the Lara PR 2 L/h 20 Bar and Nova DMPR 3.5 L/h 20 Bar models, which operate up to 20 bar, are used.
Sources
- AnTech 2025 Product Catalogue (KT_25 R02): feature lists, material code tables and electrode sets with holders for the Lara PR and Nova DMPR.
Frequently Asked Questions
What is a pH dosing pump?
It is a dosing pump that measures the pH of water with an electrode and automatically doses a pH reducer or increaser to hold the target value. At AnTech, the Lara PR and Nova DMPR series do this job.
Does the pH electrode come with the pump?
No. The electrode, holder and calibration solution are selected separately as an electrode set with holder. P-coded sets are used for pH and R-coded sets for ORP.
Can the same pump control both pH and chlorine?
No. The Lara PR and Nova DMPR measure only one of pH or ORP at a time and dose a single chemical. pH and chlorine control require two separate pumps.
At what value should pH be kept?
The target value depends on the application; there are different requirements for pools, drinking water and wastewater. Use the value in the regulations that apply to your facility; if you are unsure, write to us and we will check it together.
How often should a pH electrode be calibrated?
The calibration interval depends on water quality and operating conditions. Regularly compare the value shown by the pump with a test kit or handheld meter; when you see a deviation, clean the electrode and recalibrate it with buffer solutions.
Should I buy the Lara PR or the Nova DMPR?
For compact and more economical pH control, the Lara PR is sufficient. If you need a flow rate above 10 L/h, a 95–260 V AC supply, transmission of the measurement via 4–20 mA or ModBus communication, choose the Nova DMPR.
Which chemical is used to lower pH?
Diluted sulphuric acid, hydrochloric acid or sodium bisulphate dissolved in water are commonly used. Send us the name and concentration of the chemical and we will check its compatibility with the pump materials together.