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Sizing of the heating time

Swimming pool heating

The pools contain large masses of water that must be kept at a controlled temperature, whether they are located in theopen or closed.

The temperature at which to bring and keep the water depends on the type of activities that must take place in the pool and on the degree of comfort desired in the following table are identified ranges of temperature for different types of reservoirs.

In the heating of swimming pools, there are two different times: start-up system e maintenance. The start-up system is the increase in water temperature from the value of the aqueduct to the value of use.

This operation takes place during the first start-up of the pool and subsequently whenever necessary to empty the tank for the normal operations of maintenance and hygiene.

The time in which it can be made the start-up system varies from 24h up to 96 h.

Type of pool

Temperature ° C

competitive pool 22-24
light sport / leisure 24-28
children's pool / warm up 28-30
swimming pools for therapeutic use 29-30

Water temperatures for different types of pool

Calculation of heat loss of the pools 


The shorter the time to reach steady greater the power required to the generator accordingly it is advisable to opt for a longer time: the power start-up system exceeds that required for the maintenance of a share greater the smaller is the time of start-up system.

Once reached the desired temperature, this must be maintained so we need to deliver a continuous heat input equivalent to the sum of the dispersions of the entire pool: this is the maintenance phase. The heat loss a pool is due to several factors:

  • Evaporation from the surface of the water;
  • radiation towards the external environment;
  • convection produced by the contact between the air and the water;
  • transmission through the walls of the basin;
  • flow rate of water daily change.

The most important item of dispersion is evaporation and depends on the size of the mirror of water, the water temperature and the air temperature and above all by its content of steam.

For reasons of comfort in indoor swimming pools, must be:

Taria ° C = Twater + (1 ÷ 3) ° C

Relative humidity RH = 50 ÷ 60% 

The phenomenon of evaporation it is accentuated by the degree of activity in the pool: in the calculation of the evaporation fraction it is necessary to resort to corrective factors to be used according to the degree of activity. Convection losses depend on the velocity of the air on the water surface.

The losses for radiationMore difficult to assess, depending on the temperature of the surfaces bounding the pool.

The above items must be added the losses due to water flow renewal daily. For hygienic reasons the conduction of the basins requires a water flow rate of renewal of at least 5% of the volume present in the tub.

Calculate the heat demand for heating swimming pools

In the following tables show the values ​​of thermal requirement for swimming pools of different type, highlighting how the dispersions vary with the temperature of the air.

Specific dispersion of swimming pools for sports W / m2
  Air temperature (° C) / Humidity
water (° C)
23 ° C / 60% 25 ° C / 60% 27 ° C / 60% 29 ° C / 60%
22 230 190 160 121
24 - 260 230 190
26 - - 290 260
28 - - - 330

Indicative of leakage from reservoirs sports

Specific dispersion swimming pools for residential use W / m2
  Air temperature (° C) / Humidity
water (° C)
23 ° C / 60% 25 ° C / 60% 27 ° C / 60% 29 ° C / 60%
22 170 150 130 110
24 - 190 170 150
26 - - 220 200
28 - - - 240

Indicative of leakage from reservoirs residential 

In important applications such as those of sports is even more significant savings achievable by heating in heat pump. Already Annex D of Presidential Decree 412/93 indicated heat pumps as technologies for the use of renewable sources or similar electively indicated for the production of energy in buildings and facilities used for sports activities and specifically for:

  • drying air temperature in indoor and heated;
  • heating ambient air in indoor swimming pools;
  • heating tank water;
  • heating hot water for showers and changing rooms.

Energy savings for heating swimming pools

Both the powers necessary for the start-up system, as those necessary for the maintenance, may be provided by heat pumps saving in terms of Costi management compared to other heating systems up to 80%.

The state of the art envisages, in particular applications such as those of the pools the interposition between the
generator and the pelvis of a heat exchanger plates of a material able to withstand the aggression of the chlorinated water.

The hydraulic circuit must be equipped in each case of filters and prefilters to protect the system and also a system by-pass the pool side to avoid the sovradimensionameto exchanger.

If you want to do the insights on heating for swimming pools heat pump, You can find valuable information at the following links:

Rossato Group Srl
Via del Murillo, km 3.500, 04013 Sermoneta LT - Italy
Share capital € 200.000,00 fully paid up - no. REA LT-107494
VAT-CF IT01745300598

Working Time
From Monday to Friday
Morning 8: 30 - 12: 30
Afternoon 13: 30 - 17: 30