How to waterproof water tanks

Waterproofing is essential for the work carried out by water tanks, those concrete infrastructures that collect, purify and distribute water, especially in view of the fact that water is an increasingly scarce resource.

Although it is true that concrete stands out for its compactness, which gives it maximum density and makes it impermeable, this is not always enough and it must be waterproofed in order to preserve its capacity to contain water and its possible deterioration.

Another problem is water getting into the concrete reinforcement, causing rusting. The waterproofing of the vessel prevents the volume of the material from increasing and cracks from occurring, causing leakage or even contamination.

How to do it, step by step

First of all, at Molins we recommend preparing the surface by removing dirt, paint and old waterproofing residues from the floors and walls of renovation tanks and the remains of weak grout in new structures. In the case of newly built tanks, it is necessary to establish an adequate design of the sealing and the concrete joints or through elements.

In tanks to be rehabilitated, damage (cracks or loss of volume) must be treated with mortars suitable for concrete repair and the joints with through elements in walls and slabs must be repaired. In the case of underground tanks, seepage problems must be stopped. In addition, half-rounds should be made in the corners of the tank to minimise stresses at the junctions between walls and slabs.

The next step is to reinforce with low grammage fibreglass mesh the singular points that require more attention and thus absorb the movements that may occur. In the case of structural joints or where higher performance reinforcement is required, a high performance elastic joint sealing system is required.

For waterproofing: wet the surface until it starts to lose its shine, then apply two cross coats of FLEXITEC with a minimum final thickness of 2 mm. Waterproofing is generally a simple process that can be carried out manually or by spraying, although a minimum of seven days is required for the product to cure properly and fill the tank permanently.

Finally, in the case of drinking water, it must be pre-washed with pressurised water for 4 consecutive days to remove any remaining dirt.

For this waterproofing process, we also have single-component membranes, such as Propam ImpeFlex, a waterproofing coating that is easy to apply and dries quickly, which acts as a physical and chemical barrier to the passage of filtration damp, applicable by brush or trowel in a thin layer, which can be applied to a wide variety of substrates and which is compatible with all types of finishes.