Metering of Flocculant in Swimming Pool Water

Swimming pool water treatment includes the metering of flocculants in order to achieve optimal filtration results. Challenge: constant and exact metering of small amounts. No Problem for ProMinent Metering Pumps.


Water filtration is a step in swimming pool water treatment that, for optimal results, requires the metering of flocculants into the water. By means of flocculants, non-filterable particles are rendered filterable. The particles that are to be filtered, so-called colloidal disperse substances, are not visible to the naked eye. As these small particles (1 µ/mm) are charged with negative energy, they can be attracted by positively charged flocculants. The compound of particles to be filtered and flocculant is filterable.


For optimal flocculation the following three criteria are relevant:

  • Acid Capacity
  • pH Value
  • Metering/Metering amount

The minimum acid capacity is of KS 4.3 0.3 mol/m³ in Whirlpools with own water treatment section and of KS4.3 0.7 mol/m³ in all other pool versions. Sodium carbonate and Sodium hydrogen carbonate can be used to correct this value (see Article "pH Regulation in Swimming Pools", right side).

When metering, the following points are to be considered:

  • Metering of flocculants has to be effected constantly and exactly as possible. Long metering breaks (longer than 2 seconds) should be avoided. Thus, the metering amounts are very small.
  • The metering amount of aluminum salts is at 0.05g/m³, ferric salts having a circulation value of 0.1g/m³. The respective metering amount is to be adjusted according to the instructions of the manufacturer on the exact concentration of the flocculants.

As very small doses are used, the metering accuracy must be very high. The metering place should be positioned a sufficient distance from the filter in order to allow an adequate reaction time. Mixing can be intensified with an appropriate mixer unit. If the flocculant metering is to be effected on the suction side of the circulation process, the problem of flocculant separation is to be observed and the metering of activated carbon should be avoided. This procedure would cause heavy wear on the circulation pump, as the metering of activated carbon is always effected before the flocculation.

The ProMinent Solution

Our Solenoid Driven Metering Pumps, Beta® and gamma/L, are ideally suitable for the demands made on the metering of flocculants. These two series pumps allow minimum metering amounts with high accuracy via stroke length and frequency adjustments.

The calibration function of gamma/L series enable exact metering, indicating the current and totalized metering amounts. With calibration of the respective medium (viscosity, density), the metering line and the entire frame conditions of the system are detected. Thus, you may be sure that exact amount of flocculants is dosed into the system.