SEKO Dosing Pump Not Priming? TEKNA Air Bleeding and Mode Checks

The TEKNA is installed, the panel light is on, the pump clicks away stroke after stroke, and the tank level doesn't move. When a SEKO dosing pump won't deliver, the usual suspects are air and suction piping, but solenoid pumps add one more category people forget about: control mode and settings. Quite often the pump is fine and a parameter is simply wrong.

Make Sure the Pump Is Really Stroking

TEKNA comes in five models, 500, 600, 603, 800 and 803, all with a PVDF head, ceramic balls and a PTFE diaphragm, and the supply range is 100-240 V. After power-up, check two things: is the power indicator lit, and can you hear a regular stroke?

No light and no sound means power or wiring. Light on but no strokes usually means the SEKO dosing pump is waiting for a signal or has been stopped externally; that's covered in the mode section below. Strokes but no chemical is the genuine "won't prime" case.

SEKO Dosing Pump Won't Prime: Air and Suction Line

Gas in the head

A solenoid pump displaces only a small volume per stroke, so a little gas in the head and the diaphragm is just compressing air. With gassing chemicals such as sodium hypochlorite or hydrogen peroxide, a pump that sat overnight and won't prime in the morning is completely normal.

The SEKO brochure's typical installation drawing is labeled as an installation with a degassing head, and it shows a priming valve and a back pressure valve on the discharge side. If your SEKO dosing pump has that priming valve, open it after starting the pump so gas and chemical return to the tank through the return tube, and close it once you see a steady flow of liquid. For gassing chemicals, ask about the degassing head at the ordering stage. It beats bleeding by hand again and again.

Suction tubing and foot filter

Each TEKNA SEKO dosing pump ships with a foot filter, an injection valve, 2 m of PE discharge tubing and 4 m of PVC suction tubing. You don't have to use all 4 m. If the tank sits next to the pump, cut the suction tube shorter for less suction resistance and fewer places for air to get in.

The foot filter sits on the tank bottom, and once sediment cakes the screen, nothing comes up. A suction fitting that isn't compressed properly lets the pump pull air. One more trap when changing models: the 500, 600, 603 and 800 use small tubing with a 4 mm inside diameter, while the 803 moves up to 8/12 tubing. Swap an 800 for an 803 without changing tubing and fittings and the connection is very hard to seal.

Wrong Control Mode Looks Like a Dead Pump

On SEKO dosing pump service calls, this is the most common situation, and the pump itself has nothing wrong with it.

AKS frequency range. The AKS adjusts flow with a knob and has two frequency ranges, 0-20% and 0-100%. Left on 0-20%, even a fully turned knob gives a very low stroke rate. The pump moves, but the output is too small to notice.

APG pulse ratio. The APG takes a 4-20 mA signal or a pulse signal from something like a water meter, and offers four pulse ratios: 1:1, 4:1, 10:1 and 1:N. Pick the wrong ratio and the pump doses far less than expected. If the water meter isn't sending pulses, the pump doesn't stroke at all.

TPG and TPR remote start/stop and level. The TPG has a remote on/off input; the TPR can be started and stopped by an external signal, and it has a level input with low-level alarm. If the external stop signal is always present, or the level probe is mounted wrong, the SEKO dosing pump stays idle. The TPR also adjusts flow from its pH/ORP reading, so when the reading is already at setpoint, it doses less or not at all by design. That isn't a fault; check that the probe reading is accurate first.

Match the Pressure Rating

On every TEKNA SEKO dosing pump, flow and pressure are given as pairs, and the more flow, the less pressure it can handle. The 803 is the extreme case: 54 L/h only applies at 0.1 bar, and at 20 L/h it can reach 5 bar. Run an 803 flat out into a pressurized line and almost nothing gets in. The 600 reaches 20 bar at 2.5 L/h but only 8 bar at 5 L/h. If the injection point pressure is high, step back to a suitable model for the actual pressure.

Too little pressure is also a problem. The chemical siphons and flow swings around. Fit a back pressure valve on the discharge so the SEKO dosing pump always works against a stable pressure.

Servicing Valves and Seals

Two points when cleaning the valve assemblies: mark the orientation before removal, and don't flip them on reassembly. Ceramic balls don't corrode, but seats and seals age. TEKNA seals come in FPM and EPDM, with 0 for FPM and 1 for EPDM in the model code. Acids and alkalis need different materials, and a seal that swells after a chemical change can leak and stop the pump priming.

SEKO says the diaphragm is solid PTFE with a service life of more than 5 years. So on a SEKO dosing pump the diaphragm can go to the end of the list; work through air, piping and settings first.

Prevention

Use a level probe in the tank with a model that has the level input, so the pump alarms at low level instead of running dry and pulling air into the line. Lift out and rinse the foot filter on a schedule that fits the chemical, and with crystallizing chemicals, circulate clean water for a few minutes before shutdown. Write the AKS range and APG ratio on a tag next to the pump after commissioning, so the next shift has one less thing to get wrong.

Conclusion

When a TEKNA SEKO dosing pump won't deliver, go in this order. Confirm power and strokes, bleed gas from the head, check suction tubing, foot filter and fittings, then verify the AKS range, APG pulse ratio and TPG/TPR start/stop and level signals, and finally check the pressure rating and seal material. On solenoid pumps, settings cause a bigger share of "no dosing" calls than most people expect.

FAQ

Should I take the SEKO dosing pump head apart first?

No rush. Bleed the air, then check the suction line and settings. Most problems are solved in those two steps.

My 803 at full output delivers less than an 800. Why?

The 803's maximum flow only applies at 0.1 bar. With pressure in the line, its output drops sharply. Use the curve for the actual pressure when picking a model.

The SEKO dosing pump is wired to a water meter but never strokes. What's wrong?

Check that the meter is actually sending pulses, then check the APG ratio. In 1:N mode with a large N, the pump has to collect many pulses before each stroke.

After switching chemicals my SEKO dosing pump leaks and won't prime. Why?

The seal material probably doesn't suit the new chemical. Check FPM or EPDM compatibility and replace the seals if needed.

Can I service a SEKO dosing pump myself?

Cleaning the foot filter, injection valve and valve assemblies is fine. Stop the pump, release the pressure and wear protection first. Leave control board and solenoid problems to an authorized service channel.

Still no flow after all that? Send us the model code, chemical and an installation photo through our contact page and we'll take a look.