Installation: Henden pH Dosing Pump HPHD Owner Manual

Content

Overview

The pH Dosing Pump HPHD is an automatic acid dosing pump designed to help keep pool water balanced by measuring pH and dosing diluted acid when the water becomes too alkaline. It is intended for residential pools and works alongside the filtration system so chemical correction happens only during normal circulation.

This guide is aimed at pool owners, installers, and service technicians who need a clear, practical explanation of how the pH Dosing Pump HPHD is installed, calibrated, maintained, and troubleshot.

Specifications

Model: HPHD
Function: Automatic pH control with acid dosing
Display: Digital LCD
Power supply: 230-240 V, 50/60 Hz, single phase
Enclosure rating: IPX4
Approximate dimensions: 120 mm deep, 105 mm wide, 140 mm high
Probe calibration reference: pH 7 buffer solution
Set point range: 7.0 to 7.6 pH
Recommended operating pH range: 7.2 to 7.6
Maximum recommended system pressure: 1 bar, never above 1.5 bar
Compatible installation: Suits existing Henden chlorinators and other non-Henden chlorinators in Australia
Supply connection: 3-pin piggyback plug and lead
Warranty period: 2 years

Detailed description

The pH Dosing Pump HPHD measures pool water pH through a probe installed in the circulation line. When the reading moves away from the target value, the controller activates the peristaltic pump to draw diluted acid from a storage container and inject it into the plumbing system. The dosage is proportional, so the pump shortens or lengthens its run time based on how far the water is from the set point.

The package includes the peristaltic pump, PVC tube, pH probe with protective cap, foot filter, injection valve, pipe clamp, pH 7 buffer solution, mounting hardware, inline electrode holder, and shutter washer. The controller uses a simple front-panel interface with SET and CAL buttons, plus a pH display that shows the measured water value and operating status.

Safety

The pH Dosing Pump HPHD must be installed by a person who understands swimming pool plumbing and electrical requirements. It is not suitable for use by children or by anyone who cannot operate it safely without supervision.

Never connect the unit directly to mains power. It must run from the chlorinator power supply so dosing follows the filtration cycle. Keep the unit dry, avoid wet-hand handling, and disconnect power before any service work. Pressure must also be relieved from the pump head or injection line before maintenance begins.

Because the system handles acid, protective clothing is essential. Gloves, goggles, and overalls should be used when mixing, filling, or servicing the dosing system. Only use containers, tubing, seals, and valves that are suitable for hydrochloric acid.

Pool acid must always be diluted carefully. For pools up to 100,000 litres, the recommended mix is 5 parts water to 1 part acid in a suitable 20-litre container. For pools above 100,000 litres to 160,000 litres, use 3 parts water to 1 part acid. The hydrochloric acid strength must not exceed 28 percent.

Install the controller in a dry location away from heat and where ambient temperatures do not exceed 45°C. The pH probe must be positioned before any heater or electrolyser, and the injection valve must be the last item in the pipework.

Setup and operation

Mount the pump on the wall using the bracket and fixings supplied. Drill suitable holes for the wall type, secure the bracket, and slide the pump into place. The clamp assembly is fitted to the pipework, with separate openings for the injection valve and the pH probe.

Install the probe holder carefully and insert the probe without crushing the body. The probe tip should sit partway into the pipework, and the lead connects to the BNC terminal on the controller. Keep at least 200 mm between the probe and the injection valve to reduce interference and improve measuring stability.

Plumb the tube from the pump and foot filter to the injection valve by sliding the nut over the tube, seating the tube on the conical nipple, and tightening the nut by hand. Use thread seal tape on the injection valve threads where required.

After plumbing, connect the unit through the chlorinator so the pump runs only during filtration cycles. If the pool pump is already plugged into the chlorinator, move that plug to the chlorinator socket through the pH pump’s piggyback connection, then connect the pool pump to the female socket on the pH pump lead.

To calibrate the probe, stop the filtration pump, close any isolation valves, remove the probe, and seal the holder opening with the shutter washer. Rinse the probe in tap water for at least 20 minutes, then place it in the pH 7 solution. After the value stabilises, press CAL until the display flashes CAL, then release and complete the calibration process.

The set point can be adjusted by pressing SET to display the current value and then pulsing CAL to change it in 0.1 pH steps between 7.0 and 7.6. The factory set point is 7.4 pH. In normal use, the pump reduces dosing as the reading approaches the target and may remain off for long periods, which is normal.

The display backlight turns off after 30 minutes without key activity to save energy. A short press on SET or CAL restores the light.

Cleaning and maintenance

The peristaltic tube is a wear item and should be checked regularly for leaks or damage. Replacement is generally recommended about once a year, while the roller holder should be inspected periodically and replaced about every two years.

The pH probe can develop scale and contamination over time, especially in hard or mineral-rich water. Regular calibration every three to four weeks, or sooner if chemical consumption changes abnormally, helps maintain accuracy.

For winter storage in freezing areas, remove the peristaltic tube, flush it with fresh water, dry it fully, and reinstall it only after it is completely dry. The pH probe should be removed, fitted into its protective cap, and stored with the cap filled one-third with fresh water.

Troubleshooting

If CAL Err appears during calibration, the most likely causes are a faulty probe, contaminated buffer solution, or moisture/oxidation in the probe connector. Replace the affected part or repeat the calibration with fresh buffer solution.

If Alr Err appears, the measured pH is outside the safe operating range, below 5 or above 9. Dosing stops automatically until the water chemistry is corrected. Adjust the pool manually by checking total alkalinity, hardness, and pH, then allow the controller to resume once the reading returns to range.

If probe readings become unstable or abnormal chemical use is noticed, recalibrate the system and inspect the probe, connector, and buffer solution before continuing operation.

Warranty

The pH Dosing Pump HPHD is covered by a two-year guarantee. The coverage includes repair, replacement, or refund rights where the product fails under Australian Consumer Law, subject to the conditions stated by the manufacturer.

The warranty does not cover normal wear, misuse, negligent handling, improper installation, failure to follow operating instructions, lack of maintenance, corrosive or abrasive liquids, lightning or power surges, or repairs attempted by unauthorized persons.

Pros & Cons

Pros: Automatic pH correction, proportional dosing control, easy set-point adjustment, clear digital display, and compatibility with chlorinator-based systems.
Pros: Includes calibration buffer, probe hardware, mounting parts, and tube connections in the box.
Pros: Designed for safe operation during filtration cycles and supports regular pool maintenance routines.
Cons: Requires careful installation, regular probe calibration, and periodic replacement of wear parts such as the peristaltic tube.
Cons: Must be installed with proper acid handling practices and cannot be connected directly to mains power.

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Faqs

How do I install the pH Dosing Pump HPHD so it works only with the pool filtration cycle?

The HPHD should be installed in a dry, well-ventilated area away from heat and protected from weather exposure. It must not be connected directly to mains power; instead, it should be linked to the chlorinator power supply so it runs only when the filtration pump is on. This helps the dosing pump operate during preset filtration cycles and supports safer, more controlled pH dosing.

Where should the pH probe and injection valve be positioned in the pool plumbing?

The pH probe must be installed before any heater or electrolyser so it reads the pool water correctly. The injection valve should be placed last in the pipework, and there must be at least 200 mm between the probe and the injection point. The probe tip should sit roughly halfway into the pipe flow for accurate measurement without being forced too deeply into the line.

How do I connect the HPHD to the chlorinator and pool pump?

For the recommended setup, remove the pool pump plug from the chlorinator socket, plug the HPHD piggy-back lead into that socket, and then connect the pool pump to the female socket on the back of the HPHD power lead. This arrangement lets the dosing pump follow the chlorinator’s filtration timing. It also helps prevent the unit from running when circulation is off, which is important for safe acid dosing.

What is the correct water and acid dilution ratio for pH dosing with the HPHD?

The manual recommends diluting hydrochloric acid before it is dosed into the pool. For pools up to 100,000 litres, the ratio is 5 parts water to 1 part acid. For pools above 100,000 litres and up to 160,000 litres, the ratio is 3 parts water to 1 part acid. The manual states the acid strength should not exceed 28%, and the mixture should be kept in a suitable ventilated container.

How do I calibrate the pH probe on the HPHD?

To calibrate the probe, stop filtration, close any isolation valves, remove the probe, and fit the shutter washer to seal the holder opening. Rinse the probe in tap water for at least 20 minutes, then place it in the pH 7 buffer solution and wait until the reading stabilises. Press CAL until the display flashes, then release. Reinstall the probe after calibration and repeat this process regularly for accurate readings.

Why does the HPHD often show the pump as off during normal operation?

This is normal behaviour. The HPHD uses proportional dosing, so it reduces its dosing time as the pH reading gets closer to the set point. When the water is already near the target, the pump spends more time idle because only a small correction is needed. The unit may appear to switch off frequently, but that simply means it is adjusting dosage gradually to avoid over-correcting the pool water.

How do I change the pH set point on the HPHD controller?

Press SET to display the current set point, then press SET again and use CAL in short pulses to adjust the value. Each pulse changes the pH target by 0.1, within the range of 7.0 to 7.6. The factory default is 7.4. This makes it easy to fine-tune pool water balance while staying within the manual’s recommended pH operating range of 7.2 to 7.6.

What should I do if the HPHD shows a CAL error or Alr error?

A CAL error during calibration usually points to a faulty pH probe, contaminated buffer solution, or moisture in the probe connector. Replace the probe, use fresh buffer solution, and check the connector for water or oxidation. An Alr error means the pH is outside the safe dosing range, below 5 or above 9, and dosing stops automatically. In that case, correct the pool chemistry manually before the controller can resume normal operation.