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Water Tank Replacement
Replace or Refurbish? (Replacement Advice)
Most engineers who replace their steel water storage tanks for brand new Glass Reinforced Plastic (GRP) water storage tanks believe that water tank replacement is the ‘ultimate’ solution. Unfortunately, having now repaired and relined literally hundreds of GRP water storage tanks, we know this not to be the case. COVAC are constantly asked to carry out water tank repair and reline GRP water storage tanks, some of which are only months old. This is because the problem faced by all engineers who are responsible for the maintenance of GRP tanks is that even with regular cleaning and chlorination, bacteria such as micro-aquatic organisms will continue to multiply as they are protected in the habitat provided by air filled cavities and fine cracks that often cannot be seen with the naked eye. These cavities and cracks in the internal substrate allow bacteria to nest and proliferate.
The problems start to occur when the water molecules migrating into the GRP tank encounter other chemicals inside the laminate, primarily water-soluble materials (WSMs) such as the emulsion binders used to hold the glass mat together before it is moulded. The water molecules can then have a chemical reaction with these substances, forming larger molecules of a new chemical, often acidic – which unlike the original small water molecules, cannot carry on passing through the GRP. These larger molecules are then trapped. This is the point at which osmosis actually starts.
Osmotic blistering of the GRP substrate due to water permeation can also lead to deterioration of the gel coat and, subsequently, a surface which is highly likely to harbour and promote the growth of micro-aquatic organisms.
It should be borne in mind that, if ignored, such internal water osmotic blisters will eventually burst putting their contents into the potable water. These chemicals not only have a very unpleasant taste but are also toxic! For this reason, GRP is not recommended or approved by the DWI (Drinking Water Inspectorate) for drinking water storage tanks.
In addition to erosion of the GRP surfaces, there can also be numerous areas of corrosion to the steel fastenings which hold the GRP tank panels together.
Black spore fungi is also common in GRP tanks and is notorious for spreading, predominantly where there is a combination of water and air at an ambient temperature. These spores tend to multiply very quickly and produce a grey or black jelly-like growth on the internal GRP surface.
Another common fault associated with GRP tanks is the deterioration of the mastic used between the sectional GRP tank panels and the subsequent leaking of water. The mastic commonly used in these joints often deteriorates rapidly following years (sometimes months) of use and this, combined with the excessive structural movement of the plastic and the chemical dosing regime will lead to the eventual leaking of the tank from these jointed areas. The consequential loss of water through these joints can be catastrophic.
In our experience, there is usually no regress to the original manufacturer / supplier of the GRP tank because they predominantly only offer a maximum of 12 months guarantee and do not guarantee the tank against leaking!
In most cases, repairing and refurbishment of a water storage tank or cooling tower repair is far more cost effective than water tank replacement and downtime of water services and general disruption to your business will usually be far less. Following refurbishment using 3M™ Scotchkote™ Urethane Coating 165PW, structures are also very easy to clean due to the ceramic, tile-like finish of the product, meaning that your Legionella treatment programme will be far more effective.
In addition, many manufacturers of new water storage tanks and cooling towers do not offer the Ten Year "Single Source Responsibility" Guarantee that is offered by COVAC and endorsed by 3M when we refurbish any type of structure.
Impact on the environment must also be considered, we must all endeavour to minimise wastage and recycle materials as far as possible.
How will you remove and dispose of your existing water storage tank and how much extra will this and re-installation of a new water storage tank cost? This can prove very expensive with consistently increasing labour costs and the ever tightening environmental legislation regarding waste disposal for businesses.
How can we Help?
3M™ Scotchkote™ Urethane Coating 165PW has been proven to resist the growth of bacteria, such as micro-aquatic organisms and will also prevent further corrosion of steel and / or erosion of concrete and GRP surfaces, which is also an excellent nutrient source for microbial growth.
Once 3M™ Scotchkote™ Urethane Coating 165PW is applied and fully cured the internal surfaces of the structure are left with a smooth, tough, ceramic, tile-like finish, which is both easy to maintain and extremely easy to clean. Application of 3M™ Scotchkote™ Urethane Coating 165PW to the structures internal surfaces will dramatically reduce the risk of further deterioration of the surface substrate and contamination of the down services with the supply of unhygienic water to the outlets. 3M™ Scotchkote™ Urethane Coating 165PW will always produce a quality water tank coating.
