How to prevent
corrosion damage in
swimming pool buildings

Tuesday, April 25, 2017


An indoor swimming pool will offer countless hours of fun and relaxation if built and maintained the right way. However, choosing the wrong materials or not ensuring the right composition of chemicals in the water will put an end to the good times very quickly.

The environment of an indoor swimming pool is aggressive, due to both the temperature, humidity in the air and the chemicals added to the water.

This is why it is very important that the materials used in a dehumidifier are corrosion-protected. Otherwise, the lifetime of the product will be all too short.

Sign up to receive our extensive “Swimming Pool Dehumidification Selection Guide” right here.

Never mix comfort ventilation and swimming pool ventilation


The most fundamental mistake you can make when deciding how to dehumidify your indoor swimming pool is to make use of ordinary comfort ventilation.

Components in comfort ventilation units are not manufactured to withstand the aggressive environment of a swimming pool. This means you have to ensure that the building’s comfort ventilation is not merged with the swimming pool ventilation.

The best materials for dehumidifiers


The basic materials used in a dehumidifier for heat exchangers, fans, and surfaces is categorised in different corrosion classes depending on the required lifetime.

We recommend that the basic material is aluminium or hot-dip galvanised steel that has been powder coated. The heat exchangers should be made of aluminium that is epoxy-protected and coated.

The evaporators and condensers particularly need to be well protected, firstly with a primer of epoxy coating followed by a top coating.

In general, galvanised steel or powder coated aluminium are the only materials suitable for swimming pool environments. Standard stainless steel should be avoided.

 Dantherm Heat Exchanger

The right blend of chemicals is crucial


The aggressive environment of indoor swimming pools has a lot to do with the chemicals added to the water. Treating the water with too much chlorine will increase the risk of corrosion of the inventory inside the pool room and the swimming pool’s technical room.

An inaccurate blend of chemical ingredients in the water could destroy all of the inventory very quickly, including the dehumidifier and other equipment that has been installed to process the air.

Another very important issue, when it comes to adding chemicals, is of course the health of the people using the swimming pool.

Insufficiently treated water results in poor hygiene, while water that has been treated excessively results in gases in the air containing chlorine which can irritate the eyes and cause breathing difficulties.

Chemical threshold values

Shown below are the threshold values for products for indoor swimming pools in accordance with EN/ISO 12944-2, protection class C4. Complying with these values is needed to for a warranty to be valid.

When adding chemicals:

Free chlorine:                1.0 - 2.0 PPM
Combined chlorine:        Max 1/3 of the free chlorine content
pH:                               7.2 - 7.6
Total alkalinity:              80 - 150
Calcium hardness:         250 - 450
Total dissolved solids:    < 2,000
Sulphates:                    < 360

When adding chemicals:

Salt (NaCl):                  < 30,000
Total dissolved solids:    < 5,500
pH:                              7.2 - 7.6
Total alkalinity:             80 - 150
Calcium hardness:        250 – 450
Sulphates:                   < 360

So, to avoid corrosion of your indoor swimming pool equipment you will have to choose materials well suited for the harsh environment of an indoor swimming pool and make sure that the chemicals added are within the threshold values.


The ultimate Swimming Pool Dehumidification Selection Guide


Selection Guide frontpage - Download nowFor a deeper dive into the specifics on choosing and dimensioning the right dehumidifier for your indoor swimming pool, please sign up for our “Selection Guide – Swimming Pool Dehumidification”.

Dantherm is a market leading supplier of energy efficient climate control solutions for customers across the globe. Ask your pool supplier for a Dantherm product.

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