North West of England Hospital

In 1997, Covac were asked to inspect a large Hornsley Bridge, Sectional, Steel Potable water storage tank, located internally in a roof top plant room within a Hospital in the North West of England. In order to comply with regulations, a Risk Assessment was completed on the tank, where the following problems were identified:

  • The internal surfaces of the tank had previously been painted with a now non (WRAS/DWI) approved Bitumen Coating, which had now reached the end of its useful life, due to non-compliance, sub-film corrosion, low film build, general deterioration and subsequent debonding.
  • If left untreated, the internal surfaces would have continued to be at risk from bacterial growth including Legionella (which can lead to Legionnaires disease), Pseudomonas and Biofilm; this can lead to further deterioration in the tank’s surface structure and contamination of the down services with the supply of unhygienic water to the outlets.
  • Numerous areas of the joints between the sectional steel panels had been leaking. Apart from the obvious problem of loss of water, there was also the more urgent problem which needed to be addressed in-so-far-as the water was starting to leak through the plant room floor and walls and traverse down into the ward below.
  • It was deemed that the roof of the plant room was too close to the roof access of the water tank and safe access and egress could not be achieved. COVAC had to formulate a solution to meet all the above parameters.

What did we do?

These images show the internal surfaces of the water tank, following draining of the tank.

Inside, before Water Tank Refurbishment Inside, before Water Tank Refurbishment Inside, before Water Tank Refurbishment Inside, before Water Tank Refurbishment

These images show the tank, having been prepared by means of dry abrasive blasting techniques. In order to gain safe access and egress, we removed one of the steel panels from the bottom of the tank, which was later replaced with a new low level hatch. This meant easy access / egress for future maintenance and cleaning.

Inside, after Blasting Inside, after Blasting Inside, after Blasting Inside, after Blasting

These images show the tank having been stripe coated with approximately 5mm nominal wet / dry film thickness of 3M Scotchkote 165PW. All areas of the tank that we deem to be potentially problematic, such as sharp edges, bolt holes and joints are given a "stripe coat" prior to the internal surfaces being completely relined. 3M™ Scotchkote™ Urethane Coating 165PW is then applied over the existing mastic in order to completely protect it and ensure that potential future leakage does not occur. 3M™ Scotchkote™ Urethane Coating 165PW has 35% elongation properties, therefore, not only will it cope with the structural movement of the tank, but also, the movement of the flexible mastic between the steel, sectional panels.

Inside, after Stripe Coat Inside, after Stripe Coat Inside, after Stripe Coat Inside, after Stripe Coat

These images show the internal surfaces of the tank following the full application of 3M™ Scotchkote™ Urethane Coating 165PW by means of Hot Applied, Plural Component Spray Equipment.

Inside, after full Refurbishment Inside, after full Refurbishment Inside, after full Refurbishment Inside, after full Refurbishment

In summary, the tank was fully relined and protected against any future corrosion and leakage and access and egress was no longer a worry for the Site Engineer.

A Ten Year Warranty was provided with this work, along with an image supported Completion Report.