Circulation, Flow Rate and Turnover

Swimming pool water is circulated around a system so that it can be

  • filtered,
  • heated and
  • chemically treated

before being returned to the pool.

Most circulation pumps work via centrifugal action. An outer casing encloses a rotating impeller that draws water in via vacuum suction. On the other side, the water is under pressure and gets forced along the pipework. The pumps need to be primed (i.e. flooded with water) at all times in order for this to happen.

Flow rate

The rate at which water is flowing through the system. Usually expressed as cubic metres per hour by a component fitted to the system pipework (usually between the pumps and filters) called a flow rate meter.

If you can’t seem to locate the flow rate meter on your pool, it may well be that it wasn’t fitted as part of the original installation (this is unfortunately quite common).

You’ll need to get one fitted as soon as possible in order to calculate the turnover time (discussed below).

Flow rate meter (large pool)
Flow rate meter (small pool)

Turnover time

This is the time it takes to circulate the pool volume around the treatment system.

Calculated by dividing the pool volume by the flow rate.

If the turnover time of a pool is too long, pollution levels will start to build up. If the turnover time is too short, the water will be travelling too fast through the system and this will have a negative impact on the effectiveness of the filtration system (slower filtration is usually better than faster filtration).

If you have a flow rate meter fitted to your system, work out your pools turnover time and make a note of it here.

See how it compares to the recommended turnover times given in the drop-down above.

This information is important to include in the Normal Operating Procedures (NOP) document.

Common Circulation Problems