Adding chemical products "by eye", with a bucket and a rough measure, is an image very much associated with home pool maintenance. But as soon as bathers are present, regulations no longer allow it, and there's a good safety reason behind it.

Automatic dosing, drop by drop

The pump injects small doses of product into the return line, based on what the probes measure. In a peristaltic pump a rotor squeezes a flexible tube, so the product never touches any mechanical part.

What the regulations say

Chemical products may only be added to the pool water manually when carrying out a shock treatment, and always with no bathers present, who can only use the pool again once the physicochemical parameters are back within permitted values. With bathers present, the dosing of chemical products must be automatic or semi-automatic, with no exceptions.

Why this requirement existsPouring concentrated chlorine directly where people are bathing is a real risk of irritation or chemical burns. Automatic dosing releases the product in a controlled, constant way, avoiding those concentration spikes.

What a dosing pump is

These are a type of special pump used to correctly dose a chemical substance into a water stream, a tank, or any system where the concentration of that substance (chlorine, polymers, sodium metabisulfite, pH regulators...) needs to stay constant over time.

The 2 most common types

Diaphragm pump

Pulse-driven push

  • Doses with the movement of a flexible diaphragm
  • The usual choice for medium and high flow rates
Peristaltic pump

Tube compression

  • The product never touches any mechanical part
  • Very common with especially corrosive products
  • Diaphragm pumps: dose through the movement of a flexible diaphragm that pushes the liquid with each pulse.
  • Peristaltic pumps: dose by progressively compressing a flexible tube, so the chemical product never touches any mechanical part, very common with especially corrosive products.

Both types need to be regulated and calibrated periodically, to make sure the amount of product they're actually delivering matches the amount programmed.

Which products they dose

Disinfectant (chlorine), pH regulators, flocculant and algaecide, any product whose concentration needs to stay within a constant range, without the peaks and troughs typical of occasional manual dosing.

How it relates to the rest of the system

Automatic dosing works together with water parameter measurement, the system doses based on the actual chlorine and pH readings, not on a fixed schedule, adjusting to the pool's real use at each moment of the day.