Early Stage Development of Large Scale Water Tanks
Large scale cold water storage can be traced back to medieval times. Here the construction of castles and fortified buildings led to bloody battles for ownership. If the invading armies could not gain access to the castle by the original attack then they would set up camps close by and starve the troops out. To overcome this threat, these buildings increasing in size and complexity to include areas to store food, livestock, and most importantly water to sustain everyone. Edinburgh Castle is originally an 11th century building that followed the route of building a water storage tower in the 15th century to protect itself for this very threat. Both castle and water tanks are still intact and can be visited to this day.
As populations have grown and settled in larger towns and cities, the technologies surrounding the water industry have also evolved to provide large scale water storage solutions needed to keep pace with the growth. For many centuries water storage tanks were limited in size as the hydrostatic pressure from the tank would cause the delivery pipes to crack or expose holes in the construction therefore disrupting supply. As the materials used to create water pipes improved over the centuries then it allowed the water storage tanks to become larger and more reliable.
From the second half of the 19th century, indoor plumbing became more prevalent within developed countries. Up until this point in history, indoor plumbing was only available to the super rich. To cope with this demand, local towns would construct large water storage tanks within the town rather than on the outskirts. Many of these became spectacular buildings that sat well within their local environment and many still exist because of the beauty and quality of construction, albeit with a new role.
These large scale water tanks are often described as “water towers”. A water tower is an elevated structure supporting a water reservoir constructed at a height sufficient to pressurize the water and distribute it around the pipe network. As populations continued to grow, then the technologies needed to match this expansion. The development of prefabricated concrete sections allowed water towers to be built quicker and cheaper. There are still many examples visible in the landscape. Some disguised and others made elaborate to stand out.
Control of Water-Borne Diseases
Contaminated water has been, and continues to be one of the biggest killers of the human population throughout history, even more than those killed by all the wars. In the last few hundred years, humanity has begun to understand that water-borne diseases are vastly reduced by the provision of proper sanitation and availability of fresh water.
By the early 20th century most people in the UK had piped water supplies and sanitation. Each area organised its own water and sewerage services, often by an individual Act of Parliament or Royal Charter.
This meant that at the end of the Second World War there were more than 1,000 bodies involved in the supply of water and around 1,400 bodies responsible for sewerage and sewage disposal. Most of these were local authorities.
In the last fifty years, the number of water authorities has significantly reduced to provide savings and some investment for rural communities. It has also lead to a greater number of pieces of legislation aimed at reducing the incidences of disease or death from contaminated water. It is now a highly regulated industry because it understands its history and the potential for very dangerous diseases to develop.
Key Criteria for Cold Water Storage Tank?
If you are specifying a cold water storage tank you must ensure that the supplier of the
tank and all the ancillary material has a WRAS approval certificate.
First and foremost, the material that the tank is constructed from must be inert and not be capable of changing the chemistry of the water. The tank should be capable of being cleaned and chlorinated internally without changing or damaging the tank surface. The materials used for water tanks are primarily driven by the size and the economics of manufacture. Generally smaller scale water storage tanks are made from Glass Reinforced Plastic (GRP).
These can range in size from 1m³ to 1000m³ and will not be any higher than 4m in height. These can be either a “one piece” tank built on a single mould tool (see image ‘One Piece GRP Water Tank’) or a sectional tank built from pre-fabricated panels and bolted together on site.
Larger scale water storage tanks are normally deemed to be over 1000m³ and heights over 4m.
In this segment of the market, the material choice is wider and is driven by the structural strength required to support the tank’s weight and the weight of the water and not collapse. The materials can be concrete or steel, and the steel can be stainless, galvanised or epoxy coated. Some of these options also require the use of a WRAS approved liner material; again it must be inert and not be capable of changing the chemistry of the water or be affected by the cleaning and chlorination processes.
All cold water storage tanks must be completely sealed units that are capable of stopping light, dust, and vermin from entering the water supply, as this could contaminate the “wholesome water” and spread diseases.
A cold water tank and lid for the storage of “wholesome water” shall be fitted with insulation to help prevent water from freezing and also help keep the water as cool as practicable, ideally less than 20°C. Insulation will be applied to the lid and the four walls of the tank and for those tanks in boiler rooms or other areas experiencing high heat levels, insulation should also be applied to the base. The minimum (u) value for the insulation should be 2.5 W/m²K. The (u) value, thermal conductance, is a measure of the ability of an object to allow the flow of heat from its warmer surface through the object to its colder surface.
It’s how a cup of tea gets cold when not drunk. The W is a watt, a unit of power. Light bulbs are graded by this method. The m² is the surface area of the tank. K is the isolation value of a building; it defines how a building will lose heat.
Every water tank will be fitted with an inlet pipe and valve to provide the water supply to fill the space.
The inlet valve can sometimes also be known as ball, fill or float valve (see image ‘Inlet Valve’) because they all use an air filled sealed float to set the level of water within the tank. As the water rises so does this float, and there is a rod between the float and the valve mechanism. Eventually, the float is pushed high enough to close off the valve controlling the inlet water supply.
Cold water storage tanks must also have the ability to have a warning and/or overflow pipe fitted (see image ‘Screened Overflow’).
The purpose of the warning pipe is to provide a visual indication that the inlet valve is no longer closing off the supply of water into the tank. The warning and/or overflow pipes should be installed in a prominent position where someone can see the water escaping and question why water is leaking from the tank.
The warning pipe and overflow pipe appear to carry out the same task so why would you install both?
Warning pipes are installed closer to the agreed water level within a water tank than an overflow pipe.
It would also be smaller in diameter than an overflow pipe, as its key function is to provide a visual indication that the inlet valve needs adjustment or replacement. This hopefully minimises water loss and cost to the organisation.
The overflow pipe is fitted in a higher position in the tank but still below the inlet supply. If the water level continues to rise then the overflow will allow the water to escape to a drain area to ensure that the building is not damaged or flooded. The overflow pipe will be double the size of the inlet pipe to ensure that the tank will never fill beyond a safe point, which may cause damage to the tank and the building and its contents.
An overflow pipe will always be piped towards a safe and appropriately sized drainage system, again to protect the building and its contents.
There is one more important feature that requires to be added to the cold water storage tank to allow it to operate successfully, and that it is an air vent (see image ‘Screened Air Vent’). The need to allow non-pressurised tanks to breathe is paramount. Specialised fittings are required to ensure atmospheric pressure acts on the fluid surface at all times.
Failure to meet this requirement endangers vessel construction, as well as the liquid flow in and out, could well be impaired or restricted. The air vents installed must comply with the WRAS standard and be capable of stopping light, dust, and vermin from entering the water supply but still allow air to enter. For potable water tanks, it is necessary to fit appropriate mesh screening to any atmospheric openings in the vessel construction. The Water Regulations state that no mesh should have apertures greater than 0.65mm sq.
The points highlighted above cover the key criteria for what is commonly referred to as “Byelaw 30” within the water industry. Do not be fooled that these are local authority rules, in reality, these are regulations that are governed by national parliaments or assembly under the following acts;
The Water Supply (Water Fittings) Regulations 1999, The Water Supply (Water Fittings) Regulations (Northern Ireland) 2009, and The Water Supply (Water Fittings) (Scotland) Byelaws 2014.
Will Cold Water Storage Tanks be Needed in the Future?
Do smaller scale cold water storage tanks still have a role to play within the housing, offices, or other buildings within a modern pressurised pumped water system when the supply pipes are so reliable and the ability to repair any damage is so quick? You would think the answer would be no, however, stop for a few seconds and think about how much water is used even within the home and how this has increased over the last twenty years.
More homes than ever now have dishwashers as well as washing machines. More fridges are being bought where water supply is required to make ice cubes. Higher end coffee machines are also looking for a water supply rather than filling a tank. More people are buying instant hot water boilers and water filtration to go with their normal tap. Homes now have more bathrooms than ever before with great showers and double wash hand basins. How many times a day are multiples of these running together, more than you think?
If this is how technology has evolved over the last 20 years where will it take us in the next twenty?
It would seem that cold water storage will still have an important role to play to accommodate this expansion in water usage. The pressure to construct buildings on smaller footprints will continue to grow as the population grows and urbanisation continues at a pace. There is also a demand to maximise the usable space for the client and put services into smaller and smaller areas that are less accessible. This reduction in the space allocated to services has driven the cold water storage tank manufacturers to create more sectional tanks that can be supplied on small pallets taken through smaller access doors and be built on site in more confined spaces.
The future is likely to be smaller, more flexible tanks that are easy to transport and quicker to install on site.
The drive for greater innovation will only continue.
At Nicholson’s, we pride ourselves in manufacturing and installing GRP water storage solutions of the highest quality throughout the UK.
Why work with us?
Over 50 years’ industry experience
Projects completed in the last 24 months
Nicholson Plastics is a UK GRP Water Storage Tank Manufacturer with a proven track record in the supply of water tanks to all industry sectors throughout the UK. We have an expert team on hand with over 50 Years' industry experience. Our team works hard to provide exceptional industry lead times from quotes, site visits, order processing, and delivery. We are a British Standard approved company with full certification through BSI/ISO9001 including WRAS approved certified products for potable drinking water.
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