What do you need to know about Water Tanks?

In September we published an article with information about the problems your home water may have. Today we give you more information about the tanks that store the water you consume. If you live in a building with a tank, you should be aware of some problems that could seriously compromise your health. Read on to learn more.


In the design phase of a building, it may be important to consider the need to use a tank both for water supply and as a constituent element of the fire network.


To ensure that residents are not consuming contaminated water, it is very important to carry out the diagnosis of the tank and then its rehabilitation. The diagnosis should verify its waterproofing conditions, checking possible water losses and waste entry.


Special precautions when using water supply tanks should start at the construction plan. It is essential to provide the construction plan for the special care tanks concerning water potability.



The Portuguese General Regulation of Public and Building Systems for Water Distribution and Wastewater Drainage (RGSPPDADAR) states in Article 108:


  • Building tanks are intended for the storage of water at atmospheric pressure, constituting a reserve for feeding the networks of the buildings to which they are associated.


  • The storage of water for food purposes is only allowed in cases duly authorized by the management entity, namely when the characteristics of the supply by the public system do not offer the guarantees necessary for the proper functioning of the building system, in terms of flow and pressure.


  • In the cases referred to in the previous paragraph, the managing entity shall define the constructive aspects, the sizing and the location of the tanks.



Anomalies and deficiencies

There are several cases of reservoir anomalies and deficiencies that have been noted by companies over the years to be aware of. These problems can be categorized into problems related to design, construction, operation, reservoir water status, human contact with water, and objects found within reservoirs.



Issues in the design phase:

  • Water tanks tidy in the building and not rationally placed;
  • Water tanks integrated with the cracked building structure giving rise to infiltrations;
  • Water tanks constructed of half-walled blackwater pits;
  • Water tanks in garages and atriums with floor-level mouths and vents with improper covers that do not prevent the entry of dust and spilled liquids into the reservoirs;
  • Water tanks of disproportionate length/width dimensions, with water inlet and outlet in the same vertical, giving rise to standing water at a distance, with stable foam plates and mosquitoes;
  • Water tanks with volumes disproportionate to the consumption needs, resulting in standing water;
  • Water tanks with reduced access entrances, to the point of allowing only children access;
  • Water tanks implanted in such a way that access to water inlet control valves is provided by a pneumatic boat always available inside the reservoirs;
  • Water tanks where access to water inlet control valves can only be achieved by emptying cells in series, and access to the interior by intermediate cells;
  • Water tanks with considerable areas and reduced working height, so that movement inside is only on knees;
  • Water tanks with such difficulty of access to the interior that, due to the inability to clean, were abandoned;
  • Buried water tanks, without drainage of the surrounding land, generating groundwater infiltration.



Problems in the construction phase:

  • Water tanks with slab bottom sloping in the opposite direction to sewage;
  • Water tanks with improper interior surface finish (very rough), resulting in increased contact area with water and as a consequence increased scale and difficulty in disinfection;
  • Water tanks without bottom sewage;
  • Water tanks with misplaced fishing tube relative to the bottom slab;
  • Water tanks accessible to animals such as rats, pigeons, mollusks, insects, etc .;
  • Water tanks with improper access covers and location;
  • Water tanks without vents or with floor-level vents without any protection;
  • Water tanks with trop-plein and breather without siphon, connected to rainwater or blackwater sewage;
  • Installation or expansion of water networks with new contaminated pipes;
  • Expansion of the water network with ducts with rat nests giving rise to clogging and changing water quality;
  • Water tanks without trop-plein;
  • Poorly sealed reservoir surfaces with visible steel reinforcement caused by oxidation and grouting of concrete;
  • Serial water tanks, connected at the bottom and with water entering and leaving the first reservoir, generating permanently standing water;
  • Water tanks without access to its interior;
  • Water outlet pipes at or below the bottom slab.


Exploration phase issues:

  • Water tanks in use, completely forgotten, unassisted for years, with mud in the bottom tens of centimeters thick and unqualified walls;
  • Water tanks with standing water for months or years, waiting for public water shortages to start the supply pumps;
  • Water tanks with interior surfaces completely degraded;
  • Water tanks with the strangest objects dragged during pipeline repairs after breakages;
  • Water tanks for direct use to the population, such as codfish demolishing tank;
  • Highly responsible reservoirs used as swimming pools;
  • Poorly protected reservoirs leaking buckets of dirty water, like a rainwater cover;
  • Water tanks exposed to attic temperature, with very little water renewal;
  • Water tanks uncovered in attics, subject to all dust and light;
  • Buried water tanks without protection area;
  • Water tanks enclosures where waste materials are stored without any hygienic precaution;
  • Water tanks too ventilated, not ventilated and without light protection;
  • Ventilation openings without protective nets;
  • Gardens grown on reservoirs;
  • Forage area over reservoirs or grazing domestic animals.


Problems related to reservoir water status:

  • Water covered by hydrocarbon film;
  • Surface dust films forming continuous layer;
  • Water surface, giving evidence of fermentation;
  • Smelly waters;
  • Waters with tadpoles, larvae and live worms;
  • Waters of black animals, similar to “fur-lined buttons”;
  • Water quality control, incipient, even when assisted by responsible entities.



Problems created by human contact in water tanks:

  • Lack of care and sense of responsibility towards water or personnel without any specific training;
  • Personnel in contact with water without any sanitary control;
  • Day-to-day use of clothing and shoes without gloves when in contact with the inside of the shells;
  • Absence of any visual or physical limitation of human movement in treatment or pumping stations, even when they are covered by metal grids;
  • Local authorities smoking and drinking at the time of disinfection of the reservoirs with hypochlorite solution;
  • Buried reservoirs, without drainage of the surrounding land, generating groundwater infiltration;
  • Wash the operator’s footwear in the reservoir water at the end of the work period.


Objects found inside water tanks in service:

  • Putrescent remains of building materials;
  • Remnants of paint and solvents;
  • Tools;
  • Old papers;
  • Old clothes;
  • Shoes;
  • Cigarette butts;
  • Trash containers;
  • Food pans;
  • Live mosquitoes – colonies;
  • Shellfish;
  • Small reptiles;
  • Fecal waste;
  • Dead animals: rats, doves, small reptiles, mollusks, etc.;
  • Spent batteries;
  • Plastics;
  • Cans;
  • Bottles



SEE ALSO: What problems can your home water have?


Entrust us with the rehabilitation of your reservoir

At Prudencio we are often called upon to rehabilitate or reactivate reservoirs, which have been deactivated many times over several years, to ensure the water pressure of buildings with pressure problems on the top floors. Adequate waterproofing of these reservoirs must be ensured so that rehabilitation is carried out safely and effectively.


Contact us for the diagnosis and repair of your reservoir and be aware of our special condominium conditions.


We rehabilitated your reservoir by applying Köster TPO Aqua membranes. These waterproofing membranes meet the strictest hygienic requirements for drinking water environments.



Source: Building tanks for human consumption and other purposes – Design criteria and constructive characteristics. Author: André Martins Aires Cruz Rua

Master dissertation presented to the Faculty of Engineering of the University of Porto in the Scientific Area.

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