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Thames Water Tank Base Coating, London

THE PROBLEM

The originally applied protective coating/screed to the tank base has largely failed. Anecdotally this was thought to be as a result of lack of surface preparation prior to tank lining application.

Industrial facility with large circular metal structure, surrounded by fencing and pipes. Overcast sky adds a somber tone. Road in foreground.
Interior of an empty, rusty industrial tank with a cracked concrete floor and metal beams. Dim lighting creates a gloomy atmosphere.
Interior of an empty, rusty industrial tank with a cracked concrete floor and metal beams. Dim lighting creates a gloomy atmosphere.

THE SOLUTION

As requested we provided a quotation for the removal of the existing failed tank lining and the application of suitable replacement tank lining to the concrete tank base.

Due to uncertainty over whether a damp proof membrane was installed beneath the slab, we proposed the application of Sikagard M790. As well as offering excellent resistance to waste water and offering crack bridging, this material is also vapor permeable. This made it ideal for this application where uncertainty over the presence of a DPM meant that osmotic blistering could be a risk, and by using this tank lining system would help to mitigate this risk.

Initially the failed tank lining was removed by method of high pressure water jetting (10,000 psi) and preparing the concrete simultaneously.

Pothole filled with muddy water on a road, surrounded by damaged asphalt pieces. The surface is wet and reflective, conveying neglect and disrepair.
Close-up of a wet, gravelly road surface. The ground appears muddy with small puddles reflecting light, suggesting recent rain. Earthy tone.

Once all arisings had been removed it was apparent that whilst the concrete surface was very well prepared, a significant profile had been created.

We therefore took the decision to conduct secondary preparation in the form of vacuum controlled diamond grinding in order to lessen the peaks of the surface profile.

A large, circular concrete tank interior with dim lighting. The floor shows a textured, pale surface, and the walls are a muted, weathered green. The atmosphere feels industrial and quiet.

All surface to be coated were then vacuumed clean in order to ensure the best possible adhesion of the new tank lining, which would be disrupted if a layer of dust was present on the surface.

A metal broom sweeps across a dusty, concrete floor, leaving a cleaner strip. The image conveys a sense of cleaning in progress.

As part of our standard quality assurance when applying tank linings to concrete the moisture content of the concrete was tested and recorded.

A worker in protective gear and helmet crouches inside a large, industrial tank, examining the floor with a focused expression. The space appears worn and metallic.
A gloved hand holds a moisture meter on a rough concrete surface. The analog gauge shows moisture levels, indicating moderate moisture content.

This is not strictly required for this tank lining system as it has no substrate moisture content limitations.

To ensure the correct relative humidity and dew point as per the manufacturers recommendations indirect oil fired heating and dehumidification was introduced. Again as part of our standard tank lining quality assurance the climatic conditions were tested and recorded prior to tank lining application commencing.

Close-up of a hand holding a PosiTector gauge displaying humidity and temperature readings. The rough, wet concrete surface is visible in the background.

All prepared surface were then primed using Sikagard P770 applied by method of brush and roller at a practical coverage rate of 0.4Kg/m2.

Thames Water Tank Base 11
Interior of an industrial structure with metal beams and overhead lights illuminating the space. The floor appears wet, creating a reflective surface. Industrial tone.

Once cured the first coat of Sikagard M790 was applied in a red colour at a practical coverage rate of 0.6Kg/m2.

A worker in protective gear applies a red coating to a concrete surface. The setting is industrial, with a focus on precision and safety.

Throughout the tank lining application wet film thickness readings were taken suing thickness combs to ensure the correct tank lining thickness was achieved.

A gloved hand holds a small, notched card over a wet, shiny surface. The card has faint markings. The scene is dimly lit, creating a focused, procedural mood.

The second coat of Sikagard M790 was then applied in the same manner and consumption rate in the contrasting grey colour.

Interior of a large industrial tank filled with still, reflective liquid. Dim lighting and metal scaffolding create an eerie, vast atmosphere.
Close-up of a smooth, shiny surface transitioning from gray to green, separated by a black strip. The texture appears wet, suggesting recent cleaning.

By using contrasting colour for each layer of the tank lining system this aids applicators in achieving full and uniform coverage and is considered best tank lining practice.

The cured tank lining was tested for pin holing by method of spark testing. A single pin hole is a point of tank lining failure, making this a critical quality assurance step.

Finally the sealant at the floor/wall interface which had been removed as part of the preparation works was reinstated using Sika  TS Plus applied using sealant guns and bladed flush.

Thames Water Tank Base 17

The works from start to finish were completed in two weeks and once complete enabled the client to return the tank to full operational service.